Randomization-Based Inference about Latent Variables from Complex Samples: The Case of Two-Stage Sampling

ERIC Educational Resources Information Center

Li, Tiandong

2012-01-01

In large-scale assessments, such as the National Assessment of Educational Progress (NAEP), plausible values based on Multiple Imputations (MI) have been used to estimate population characteristics for latent constructs under complex sample designs. Mislevy (1991) derived a closed-form analytic solution for a fixed-effect model in creating…

The Analysis of Organizational Diagnosis on Based Six Box Model in Universities

ERIC Educational Resources Information Center

Hamid, Rahimi; Siadat, Sayyed Ali; Reza, Hoveida; Arash, Shahin; Ali, Nasrabadi Hasan; Azizollah, Arbabisarjou

2011-01-01

Purpose: The analysis of organizational diagnosis on based six box model at universities. Research method: Research method was descriptive-survey. Statistical population consisted of 1544 faculty members of universities which through random strafed sampling method 218 persons were chosen as the sample. Research Instrument were organizational…

Exact intervals and tests for median when one sample value possibly an outliner

NASA Technical Reports Server (NTRS)

Keller, G. J.; Walsh, J. E.

1973-01-01

Available are independent observations (continuous data) that are believed to be a random sample. Desired are distribution-free confidence intervals and significance tests for the population median. However, there is the possibility that either the smallest or the largest observation is an outlier. Then, use of a procedure for rejection of an outlying observation might seem appropriate. Such a procedure would consider that two alternative situations are possible and would select one of them. Either (1) the n observations are truly a random sample, or (2) an outlier exists and its removal leaves a random sample of size n-1. For either situation, confidence intervals and tests are desired for the median of the population yielding the random sample. Unfortunately, satisfactory rejection procedures of a distribution-free nature do not seem to be available. Moreover, all rejection procedures impose undesirable conditional effects on the observations, and also, can select the wrong one of the two above situations. It is found that two-sided intervals and tests based on two symmetrically located order statistics (not the largest and smallest) of the n observations have this property.

Sampling ARG of multiple populations under complex configurations of subdivision and admixture.

PubMed

Carrieri, Anna Paola; Utro, Filippo; Parida, Laxmi

2016-04-01

Simulating complex evolution scenarios of multiple populations is an important task for answering many basic questions relating to population genomics. Apart from the population samples, the underlying Ancestral Recombinations Graph (ARG) is an additional important means in hypothesis checking and reconstruction studies. Furthermore, complex simulations require a plethora of interdependent parameters making even the scenario-specification highly non-trivial. We present an algorithm SimRA that simulates generic multiple population evolution model with admixture. It is based on random graphs that improve dramatically in time and space requirements of the classical algorithm of single populations.Using the underlying random graphs model, we also derive closed forms of expected values of the ARG characteristics i.e., height of the graph, number of recombinations, number of mutations and population diversity in terms of its defining parameters. This is crucial in aiding the user to specify meaningful parameters for the complex scenario simulations, not through trial-and-error based on raw compute power but intelligent parameter estimation. To the best of our knowledge this is the first time closed form expressions have been computed for the ARG properties. We show that the expected values closely match the empirical values through simulations.Finally, we demonstrate that SimRA produces the ARG in compact forms without compromising any accuracy. We demonstrate the compactness and accuracy through extensive experiments. SimRA (Simulation based on Random graph Algorithms) source, executable, user manual and sample input-output sets are available for downloading at: https://github.com/ComputationalGenomics/SimRA CONTACT: : parida@us.ibm.com Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Sampling considerations for disease surveillance in wildlife populations

USGS Publications Warehouse

Nusser, S.M.; Clark, W.R.; Otis, D.L.; Huang, L.

2008-01-01

Disease surveillance in wildlife populations involves detecting the presence of a disease, characterizing its prevalence and spread, and subsequent monitoring. A probability sample of animals selected from the population and corresponding estimators of disease prevalence and detection provide estimates with quantifiable statistical properties, but this approach is rarely used. Although wildlife scientists often assume probability sampling and random disease distributions to calculate sample sizes, convenience samples (i.e., samples of readily available animals) are typically used, and disease distributions are rarely random. We demonstrate how landscape-based simulation can be used to explore properties of estimators from convenience samples in relation to probability samples. We used simulation methods to model what is known about the habitat preferences of the wildlife population, the disease distribution, and the potential biases of the convenience-sample approach. Using chronic wasting disease in free-ranging deer (Odocoileus virginianus) as a simple illustration, we show that using probability sample designs with appropriate estimators provides unbiased surveillance parameter estimates but that the selection bias and coverage errors associated with convenience samples can lead to biased and misleading results. We also suggest practical alternatives to convenience samples that mix probability and convenience sampling. For example, a sample of land areas can be selected using a probability design that oversamples areas with larger animal populations, followed by harvesting of individual animals within sampled areas using a convenience sampling method.

Assessing the Generalizability of Randomized Trial Results to Target Populations

PubMed Central

Stuart, Elizabeth A.; Bradshaw, Catherine P.; Leaf, Philip J.

2014-01-01

Recent years have seen increasing interest in and attention to evidence-based practices, where the “evidence” generally comes from well-conducted randomized trials. However, while those trials yield accurate estimates of the effect of the intervention for the participants in the trial (known as “internal validity”), they do not always yield relevant information about the effects in a particular target population (known as “external validity”). This may be due to a lack of specification of a target population when designing the trial, difficulties recruiting a sample that is representative of a pre-specified target population, or to interest in considering a target population somewhat different from the population directly targeted by the trial. This paper first provides an overview of existing design and analysis methods for assessing and enhancing the ability of a randomized trial to estimate treatment effects in a target population. It then provides a case study using one particular method, which weights the subjects in a randomized trial to match the population on a set of observed characteristics. The case study uses data from a randomized trial of School-wide Positive Behavioral Interventions and Supports (PBIS); our interest is in generalizing the results to the state of Maryland. In the case of PBIS, after weighting, estimated effects in the target population were similar to those observed in the randomized trial. The paper illustrates that statistical methods can be used to assess and enhance the external validity of randomized trials, making the results more applicable to policy and clinical questions. However, there are also many open research questions; future research should focus on questions of treatment effect heterogeneity and further developing these methods for enhancing external validity. Researchers should think carefully about the external validity of randomized trials and be cautious about extrapolating results to specific populations unless they are confident of the similarity between the trial sample and that target population. PMID:25307417

Assessing the generalizability of randomized trial results to target populations.

PubMed

Stuart, Elizabeth A; Bradshaw, Catherine P; Leaf, Philip J

2015-04-01

Recent years have seen increasing interest in and attention to evidence-based practices, where the "evidence" generally comes from well-conducted randomized trials. However, while those trials yield accurate estimates of the effect of the intervention for the participants in the trial (known as "internal validity"), they do not always yield relevant information about the effects in a particular target population (known as "external validity"). This may be due to a lack of specification of a target population when designing the trial, difficulties recruiting a sample that is representative of a prespecified target population, or to interest in considering a target population somewhat different from the population directly targeted by the trial. This paper first provides an overview of existing design and analysis methods for assessing and enhancing the ability of a randomized trial to estimate treatment effects in a target population. It then provides a case study using one particular method, which weights the subjects in a randomized trial to match the population on a set of observed characteristics. The case study uses data from a randomized trial of school-wide positive behavioral interventions and supports (PBIS); our interest is in generalizing the results to the state of Maryland. In the case of PBIS, after weighting, estimated effects in the target population were similar to those observed in the randomized trial. The paper illustrates that statistical methods can be used to assess and enhance the external validity of randomized trials, making the results more applicable to policy and clinical questions. However, there are also many open research questions; future research should focus on questions of treatment effect heterogeneity and further developing these methods for enhancing external validity. Researchers should think carefully about the external validity of randomized trials and be cautious about extrapolating results to specific populations unless they are confident of the similarity between the trial sample and that target population.

Universal-Based Prevention of Syndromal and Subsyndromal Social Anxiety: A Randomized Controlled Study

ERIC Educational Resources Information Center

Aune, Tore; Stiles, Tore C.

2009-01-01

This article reports results from a universal preventive program aimed at (a) reducing social anxiety and (b) preventing the development of syndromal social anxiety among a population-based sample of older children and young adolescents during a 1-year period. Pupils (N = 1,748) from 2 counties were cluster randomized to either an intervention or…

The Evaluation of Teachers' Job Performance Based on Total Quality Management (TQM)

ERIC Educational Resources Information Center

Shahmohammadi, Nayereh

2017-01-01

This study aimed to evaluate teachers' job performance based on total quality management (TQM) model. This was a descriptive survey study. The target population consisted of all primary school teachers in Karaj (N = 2917). Using Cochran formula and simple random sampling, 340 participants were selected as sample. A total quality management…

A Dexterous Optional Randomized Response Model

ERIC Educational Resources Information Center

Tarray, Tanveer A.; Singh, Housila P.; Yan, Zaizai

2017-01-01

This article addresses the problem of estimating the proportion Pi[subscript S] of the population belonging to a sensitive group using optional randomized response technique in stratified sampling based on Mangat model that has proportional and Neyman allocation and larger gain in efficiency. Numerically, it is found that the suggested model is…

Estimating the encounter rate variance in distance sampling

USGS Publications Warehouse

Fewster, R.M.; Buckland, S.T.; Burnham, K.P.; Borchers, D.L.; Jupp, P.E.; Laake, J.L.; Thomas, L.

2009-01-01

The dominant source of variance in line transect sampling is usually the encounter rate variance. Systematic survey designs are often used to reduce the true variability among different realizations of the design, but estimating the variance is difficult and estimators typically approximate the variance by treating the design as a simple random sample of lines. We explore the properties of different encounter rate variance estimators under random and systematic designs. We show that a design-based variance estimator improves upon the model-based estimator of Buckland et al. (2001, Introduction to Distance Sampling. Oxford: Oxford University Press, p. 79) when transects are positioned at random. However, if populations exhibit strong spatial trends, both estimators can have substantial positive bias under systematic designs. We show that poststratification is effective in reducing this bias. ?? 2008, The International Biometric Society.

Are great apes able to reason from multi-item samples to populations of food items?

PubMed

Eckert, Johanna; Rakoczy, Hannes; Call, Josep

2017-10-01

Inductive learning from limited observations is a cognitive capacity of fundamental importance. In humans, it is underwritten by our intuitive statistics, the ability to draw systematic inferences from populations to randomly drawn samples and vice versa. According to recent research in cognitive development, human intuitive statistics develops early in infancy. Recent work in comparative psychology has produced first evidence for analogous cognitive capacities in great apes who flexibly drew inferences from populations to samples. In the present study, we investigated whether great apes (Pongo abelii, Pan troglodytes, Pan paniscus, Gorilla gorilla) also draw inductive inferences in the opposite direction, from samples to populations. In two experiments, apes saw an experimenter randomly drawing one multi-item sample from each of two populations of food items. The populations differed in their proportion of preferred to neutral items (24:6 vs. 6:24) but apes saw only the distribution of food items in the samples that reflected the distribution of the respective populations (e.g., 4:1 vs. 1:4). Based on this observation they were then allowed to choose between the two populations. Results show that apes seemed to make inferences from samples to populations and thus chose the population from which the more favorable (4:1) sample was drawn in Experiment 1. In this experiment, the more attractive sample not only contained proportionally but also absolutely more preferred food items than the less attractive sample. Experiment 2, however, revealed that when absolute and relative frequencies were disentangled, apes performed at chance level. Whether these limitations in apes' performance reflect true limits of cognitive competence or merely performance limitations due to accessory task demands is still an open question. © 2017 Wiley Periodicals, Inc.

Methods for estimating population density in data-limited areas: evaluating regression and tree-based models in Peru.

PubMed

Anderson, Weston; Guikema, Seth; Zaitchik, Ben; Pan, William

2014-01-01

Obtaining accurate small area estimates of population is essential for policy and health planning but is often difficult in countries with limited data. In lieu of available population data, small area estimate models draw information from previous time periods or from similar areas. This study focuses on model-based methods for estimating population when no direct samples are available in the area of interest. To explore the efficacy of tree-based models for estimating population density, we compare six different model structures including Random Forest and Bayesian Additive Regression Trees. Results demonstrate that without information from prior time periods, non-parametric tree-based models produced more accurate predictions than did conventional regression methods. Improving estimates of population density in non-sampled areas is important for regions with incomplete census data and has implications for economic, health and development policies.

Methods for Estimating Population Density in Data-Limited Areas: Evaluating Regression and Tree-Based Models in Peru

PubMed Central

Anderson, Weston; Guikema, Seth; Zaitchik, Ben; Pan, William

2014-01-01

Obtaining accurate small area estimates of population is essential for policy and health planning but is often difficult in countries with limited data. In lieu of available population data, small area estimate models draw information from previous time periods or from similar areas. This study focuses on model-based methods for estimating population when no direct samples are available in the area of interest. To explore the efficacy of tree-based models for estimating population density, we compare six different model structures including Random Forest and Bayesian Additive Regression Trees. Results demonstrate that without information from prior time periods, non-parametric tree-based models produced more accurate predictions than did conventional regression methods. Improving estimates of population density in non-sampled areas is important for regions with incomplete census data and has implications for economic, health and development policies. PMID:24992657

Advance notification letters increase adherence in colorectal cancer screening: a population-based randomized trial.

PubMed

van Roon, A H C; Hol, L; Wilschut, J A; Reijerink, J C I Y; van Vuuren, A J; van Ballegooijen, M; Habbema, J D F; van Leerdam, M E; Kuipers, Ernst J

2011-06-01

The population benefit of screening depends not only on the effectiveness of the test, but also on adherence, which, for colorectal cancer (CRC) screening remains low. An advance notification letter may increase adherence, however, no population-based randomized trials have been conducted to provide evidence of this. In 2008, a representative sample of the Dutch population (aged 50-74 years) was randomized. All 2493 invitees in group A were sent an advance notification letter, followed two weeks later by a standard invitation. The 2507 invitees in group B only received the standard invitation. Non-respondents in both groups were sent a reminder 6 weeks after the invitation. The advance notification letters resulted in a significantly higher adherence (64.4% versus 61.1%, p-value 0.019). Multivariate logistic regression analysis showed no significant interactions between group and age, sex, or socio-economic status. Cost analysis showed that the incremental cost per additional detected advanced neoplasia due to sending an advance notification letter was € 957. This population-based randomized trial demonstrates that sending an advance notification letter significantly increases adherence by 3.3%. The incremental cost per additional detected advanced neoplasia is acceptable. We therefore recommend that such letters are incorporated within the standard CRC-screening invitation process. Copyright © 2011 Elsevier Inc. All rights reserved.

USING GIS TO GENERATE SPATIALLY-BALANCED RANDOM SURVEY DESIGNS FOR NATURAL RESOURCE APPLICATIONS

EPA Science Inventory

Sampling of a population is frequently required to understand trends and patterns in natural resource management because financial and time constraints preclude a complete census. A rigorous probability-based survey design specifies where to sample so that inferences from the sam...

Physical Activity among Rural Older Adults with Diabetes

ERIC Educational Resources Information Center

Arcury, Thomas A.; Snively, Beverly M.; Bell, Ronny A.; Smith, Shannon L.; Stafford, Jeanette M.; Wetmore-Arkader, Lindsay K.; Quandt, Sara A.

2006-01-01

Purpose: This analysis describes physical activity levels and factors associated with physical activity in an ethnically diverse (African American, Native American, white) sample of rural older adults with diabetes. Method: Data were collected using a population-based, cross-sectional stratified random sample survey of 701 community-dwelling…

Point-Sampling and Line-Sampling Probability Theory, Geometric Implications, Synthesis

Treesearch

L.R. Grosenbaugh

1958-01-01

Foresters concerned with measuring tree populations on definite areas have long employed two well-known methods of representative sampling. In list or enumerative sampling the entire tree population is tallied with a known proportion being randomly selected and measured for volume or other variables. In area sampling all trees on randomly located plots or strips...

From samples to populations in retinex models

NASA Astrophysics Data System (ADS)

Gianini, Gabriele

2017-05-01

Some spatial color algorithms, such as Brownian Milano retinex (MI-retinex) and random spray retinex (RSR), are based on sampling. In Brownian MI-retinex, memoryless random walks (MRWs) explore the neighborhood of a pixel and are then used to compute its output. Considering the relative redundancy and inefficiency of MRW exploration, the algorithm RSR replaced the walks by samples of points (the sprays). Recent works point to the fact that a mapping from the sampling formulation to the probabilistic formulation of the corresponding sampling process can offer useful insights into the models, at the same time featuring intrinsically noise-free outputs. The paper continues the development of this concept and shows that the population-based versions of RSR and Brownian MI-retinex can be used to obtain analytical expressions for the outputs of some test images. The comparison of the two analytic expressions from RSR and from Brownian MI-retinex demonstrates not only that the two outputs are, in general, different but also that they depend in a qualitatively different way upon the features of the image.

Assessment of the effect of population and diary sampling methods on estimation of school-age children exposure to fine particles.

PubMed

Che, W W; Frey, H Christopher; Lau, Alexis K H

2014-12-01

Population and diary sampling methods are employed in exposure models to sample simulated individuals and their daily activity on each simulation day. Different sampling methods may lead to variations in estimated human exposure. In this study, two population sampling methods (stratified-random and random-random) and three diary sampling methods (random resampling, diversity and autocorrelation, and Markov-chain cluster [MCC]) are evaluated. Their impacts on estimated children's exposure to ambient fine particulate matter (PM2.5 ) are quantified via case studies for children in Wake County, NC for July 2002. The estimated mean daily average exposure is 12.9 μg/m(3) for simulated children using the stratified population sampling method, and 12.2 μg/m(3) using the random sampling method. These minor differences are caused by the random sampling among ages within census tracts. Among the three diary sampling methods, there are differences in the estimated number of individuals with multiple days of exposures exceeding a benchmark of concern of 25 μg/m(3) due to differences in how multiday longitudinal diaries are estimated. The MCC method is relatively more conservative. In case studies evaluated here, the MCC method led to 10% higher estimation of the number of individuals with repeated exposures exceeding the benchmark. The comparisons help to identify and contrast the capabilities of each method and to offer insight regarding implications of method choice. Exposure simulation results are robust to the two population sampling methods evaluated, and are sensitive to the choice of method for simulating longitudinal diaries, particularly when analyzing results for specific microenvironments or for exposures exceeding a benchmark of concern. © 2014 Society for Risk Analysis.

Methods and analysis of realizing randomized grouping.

PubMed

Hu, Liang-Ping; Bao, Xiao-Lei; Wang, Qi

2011-07-01

Randomization is one of the four basic principles of research design. The meaning of randomization includes two aspects: one is to randomly select samples from the population, which is known as random sampling; the other is to randomly group all the samples, which is called randomized grouping. Randomized grouping can be subdivided into three categories: completely, stratified and dynamically randomized grouping. This article mainly introduces the steps of complete randomization, the definition of dynamic randomization and the realization of random sampling and grouping by SAS software.

Population and performance analyses of four major populations with Illumina's FGx Forensic Genomics System.

PubMed

Churchill, Jennifer D; Novroski, Nicole M M; King, Jonathan L; Seah, Lay Hong; Budowle, Bruce

2017-09-01

The MiSeq FGx Forensic Genomics System (Illumina) enables amplification and massively parallel sequencing of 59 STRs, 94 identity informative SNPs, 54 ancestry informative SNPs, and 24 phenotypic informative SNPs. Allele frequency and population statistics data were generated for the 172 SNP loci included in this panel on four major population groups (Chinese, African Americans, US Caucasians, and Southwest Hispanics). Single-locus and combined random match probability values were generated for the identity informative SNPs. The average combined STR and identity informative SNP random match probabilities (assuming independence) across all four populations were 1.75E-67 and 2.30E-71 with length-based and sequence-based STR alleles, respectively. Ancestry and phenotype predictions were obtained using the ForenSeq™ Universal Analysis System (UAS; Illumina) based on the ancestry informative and phenotype informative SNP profiles generated for each sample. Additionally, performance metrics, including profile completeness, read depth, relative locus performance, and allele coverage ratios, were evaluated and detailed for the 725 samples included in this study. While some genetic markers included in this panel performed notably better than others, performance across populations was generally consistent. The performance and population data included in this study support that accurate and reliable profiles were generated and provide valuable background information for laboratories considering internal validation studies and implementation. Copyright © 2017 Elsevier B.V. All rights reserved.

Duration of Sleep and ADHD Tendency among Adolescents in China

ERIC Educational Resources Information Center

Lam, Lawrence T.; Yang, L.

2008-01-01

Objective: This study investigates the association between duration of sleep and ADHD tendency among adolescents. Method: This population-based health survey uses a two-stage random cluster sampling design. Participants ages 13 to 17 are recruited from the total population of adolescents attending high school in one city of China. Duration of…

A robust and efficient statistical method for genetic association studies using case and control samples from multiple cohorts

PubMed Central

2013-01-01

Background The theoretical basis of genome-wide association studies (GWAS) is statistical inference of linkage disequilibrium (LD) between any polymorphic marker and a putative disease locus. Most methods widely implemented for such analyses are vulnerable to several key demographic factors and deliver a poor statistical power for detecting genuine associations and also a high false positive rate. Here, we present a likelihood-based statistical approach that accounts properly for non-random nature of case–control samples in regard of genotypic distribution at the loci in populations under study and confers flexibility to test for genetic association in presence of different confounding factors such as population structure, non-randomness of samples etc. Results We implemented this novel method together with several popular methods in the literature of GWAS, to re-analyze recently published Parkinson’s disease (PD) case–control samples. The real data analysis and computer simulation show that the new method confers not only significantly improved statistical power for detecting the associations but also robustness to the difficulties stemmed from non-randomly sampling and genetic structures when compared to its rivals. In particular, the new method detected 44 significant SNPs within 25 chromosomal regions of size < 1 Mb but only 6 SNPs in two of these regions were previously detected by the trend test based methods. It discovered two SNPs located 1.18 Mb and 0.18 Mb from the PD candidates, FGF20 and PARK8, without invoking false positive risk. Conclusions We developed a novel likelihood-based method which provides adequate estimation of LD and other population model parameters by using case and control samples, the ease in integration of these samples from multiple genetically divergent populations and thus confers statistically robust and powerful analyses of GWAS. On basis of simulation studies and analysis of real datasets, we demonstrated significant improvement of the new method over the non-parametric trend test, which is the most popularly implemented in the literature of GWAS. PMID:23394771

The non-equilibrium allele frequency spectrum in a Poisson random field framework.

PubMed

Kaj, Ingemar; Mugal, Carina F

2016-10-01

In population genetic studies, the allele frequency spectrum (AFS) efficiently summarizes genome-wide polymorphism data and shapes a variety of allele frequency-based summary statistics. While existing theory typically features equilibrium conditions, emerging methodology requires an analytical understanding of the build-up of the allele frequencies over time. In this work, we use the framework of Poisson random fields to derive new representations of the non-equilibrium AFS for the case of a Wright-Fisher population model with selection. In our approach, the AFS is a scaling-limit of the expectation of a Poisson stochastic integral and the representation of the non-equilibrium AFS arises in terms of a fixation time probability distribution. The known duality between the Wright-Fisher diffusion process and a birth and death process generalizing Kingman's coalescent yields an additional representation. The results carry over to the setting of a random sample drawn from the population and provide the non-equilibrium behavior of sample statistics. Our findings are consistent with and extend a previous approach where the non-equilibrium AFS solves a partial differential forward equation with a non-traditional boundary condition. Moreover, we provide a bridge to previous coalescent-based work, and hence tie several frameworks together. Since frequency-based summary statistics are widely used in population genetics, for example, to identify candidate loci of adaptive evolution, to infer the demographic history of a population, or to improve our understanding of the underlying mechanics of speciation events, the presented results are potentially useful for a broad range of topics. Copyright © 2016 Elsevier Inc. All rights reserved.

[Use of blood lead data to evaluate and prevent childhood lead poisoning in Latin America].

PubMed

Romieu, Isabelle

2003-01-01

Exposure to lead is a widespread and serious threat to the health of children in Latin America. Health officials should monitor sources of exposure and health outcomes to design, implement, and evaluate prevention and control activities. To evaluate the magnitude of lead as a public health problem, three key elements must be defined: I) the potential sources of exposure, 2) the indicators to evaluate health effects and environmental exposure, and 3) the sampling methods for the population at risk. Several strategies can be used to select the study population depending on the study objectives, the time limitations, and the available resources. If the objective is to evaluate the magnitude and sources of the problem, the following sampling methods can be used: I) population-based random sampling; 2) facility-based random sampling within hospitals, daycare centers, or schools; 3) target sampling of high risk groups; 4) convenience sampling of volunteers; and 5) case reporting (which can lead to the identification of populations at risk and sources of exposures). For all sampling methods, information gathering should include the use of a questionnaire to collect general information on the participants and on potential local sources of exposure, as well as the collection of biological samples. In interpreting data, one should consider the type of sampling used and the non-response rates, as well as factors that might influence blood lead measurements, such as age and seasonal variability. Blood lead measurements should be integrated in an overall strategy to prevent lead toxicity in children. The English version of this paper is available at: http://www.insp.mx/salud/index.html.

[Respondent-Driven Sampling: a new sampling method to study visible and hidden populations].

PubMed

Mantecón, Alejandro; Juan, Montse; Calafat, Amador; Becoña, Elisardo; Román, Encarna

2008-01-01

The paper introduces a variant of chain-referral sampling: respondent-driven sampling (RDS). This sampling method shows that methods based on network analysis can be combined with the statistical validity of standard probability sampling methods. In this sense, RDS appears to be a mathematical improvement of snowball sampling oriented to the study of hidden populations. However, we try to prove its validity with populations that are not within a sampling frame but can nonetheless be contacted without difficulty. The basics of RDS are explained through our research on young people (aged 14 to 25) who go clubbing, consume alcohol and other drugs, and have sex. Fieldwork was carried out between May and July 2007 in three Spanish regions: Baleares, Galicia and Comunidad Valenciana. The presentation of the study shows the utility of this type of sampling when the population is accessible but there is a difficulty deriving from the lack of a sampling frame. However, the sample obtained is not a random representative one in statistical terms of the target population. It must be acknowledged that the final sample is representative of a 'pseudo-population' that approximates to the target population but is not identical to it.

Demographic trends in Claremont California’s street tree population

Treesearch

Natalie S. van Doorn; E. Gregory McPherson

2018-01-01

The aim of this study was to quantify street tree population dynamics in the city of Claremont, CA. A repeated measures survey (2000 and 2014) based on a stratified random sampling approach across size classes and for the most abundant 21 species was analyzed to calculate removal, growth, and replacement planting rates. Demographic rates were estimated using a...

Allelic variability in species and stocks of Lake Superior ciscoes (Coregoninae)

USGS Publications Warehouse

Todd, Thomas N.

1981-01-01

Starch gel electrophoresis was used as a means of recognizing species and stocks in Lake Superior Coregonus. Allelic variability at isocitrate dehydrogenase and glycerol-3-phosphate dehydrogenase loci was recorded for samples of lake herring (Coregonus artedii), bloater (C. hoyi), kiyi (C. kiyi), and shortjaw cisco (C. zenithicus) from five Lake Superior localities. The observed frequencies of genotypes within each subsample did not differ significantly from those expected on the basis of random mating, and suggested that each subsample represented either a random sample from a larger randomly mating population or an independent and isolated subpopulation within which mating was random. Significant contingency X2 values for comparisons between both localities and species suggested that more than one randomly mating population occurred among the Lake Superior ciscoes, but did not reveal how many such populations there were. In contrast to the genetic results of this study, morphology seems to be a better descriptor of cisco stocks, and identification of cisco stocks and species will still have to be based on morphological criteria until more data are forthcoming. Where several species are sympatric, management should strive to preserve the least abundant. Failure to do so could result in the extinction or depletion of the rarer forms.

Extending cluster Lot Quality Assurance Sampling designs for surveillance programs

PubMed Central

Hund, Lauren; Pagano, Marcello

2014-01-01

Lot quality assurance sampling (LQAS) has a long history of applications in industrial quality control. LQAS is frequently used for rapid surveillance in global health settings, with areas classified as poor or acceptable performance based on the binary classification of an indicator. Historically, LQAS surveys have relied on simple random samples from the population; however, implementing two-stage cluster designs for surveillance sampling is often more cost-effective than simple random sampling. By applying survey sampling results to the binary classification procedure, we develop a simple and flexible non-parametric procedure to incorporate clustering effects into the LQAS sample design to appropriately inflate the sample size, accommodating finite numbers of clusters in the population when relevant. We use this framework to then discuss principled selection of survey design parameters in longitudinal surveillance programs. We apply this framework to design surveys to detect rises in malnutrition prevalence in nutrition surveillance programs in Kenya and South Sudan, accounting for clustering within villages. By combining historical information with data from previous surveys, we design surveys to detect spikes in the childhood malnutrition rate. PMID:24633656

Adaptive sampling in research on risk-related behaviors.

PubMed

Thompson, Steven K; Collins, Linda M

2002-11-01

This article introduces adaptive sampling designs to substance use researchers. Adaptive sampling is particularly useful when the population of interest is rare, unevenly distributed, hidden, or hard to reach. Examples of such populations are injection drug users, individuals at high risk for HIV/AIDS, and young adolescents who are nicotine dependent. In conventional sampling, the sampling design is based entirely on a priori information, and is fixed before the study begins. By contrast, in adaptive sampling, the sampling design adapts based on observations made during the survey; for example, drug users may be asked to refer other drug users to the researcher. In the present article several adaptive sampling designs are discussed. Link-tracing designs such as snowball sampling, random walk methods, and network sampling are described, along with adaptive allocation and adaptive cluster sampling. It is stressed that special estimation procedures taking the sampling design into account are needed when adaptive sampling has been used. These procedures yield estimates that are considerably better than conventional estimates. For rare and clustered populations adaptive designs can give substantial gains in efficiency over conventional designs, and for hidden populations link-tracing and other adaptive procedures may provide the only practical way to obtain a sample large enough for the study objectives.

LOD score exclusion analyses for candidate genes using random population samples.

PubMed

Deng, H W; Li, J; Recker, R R

2001-05-01

While extensive analyses have been conducted to test for, no formal analyses have been conducted to test against, the importance of candidate genes with random population samples. We develop a LOD score approach for exclusion analyses of candidate genes with random population samples. Under this approach, specific genetic effects and inheritance models at candidate genes can be analysed and if a LOD score is < or = - 2.0, the locus can be excluded from having an effect larger than that specified. Computer simulations show that, with sample sizes often employed in association studies, this approach has high power to exclude a gene from having moderate genetic effects. In contrast to regular association analyses, population admixture will not affect the robustness of our analyses; in fact, it renders our analyses more conservative and thus any significant exclusion result is robust. Our exclusion analysis complements association analysis for candidate genes in random population samples and is parallel to the exclusion mapping analyses that may be conducted in linkage analyses with pedigrees or relative pairs. The usefulness of the approach is demonstrated by an application to test the importance of vitamin D receptor and estrogen receptor genes underlying the differential risk to osteoporotic fractures.

Randomized Controlled Trial to Increase Physical Activity among Insufficiently Active Women Following Their Participation in a Mass Event

ERIC Educational Resources Information Center

Lane, Aoife; Murphy, Niamh; Bauman, Adrian; Chey, Tien

2010-01-01

Objective: To assess the impact of a community based, low-contact intervention on the physical activity habits of insufficiently active women. Design: Randomized controlled trial. Participants: Inactive Irish women. Method: A population sample of women participating in a mass 10 km event were up followed at 2 and 6 months, and those who had…

A nonparametric method to generate synthetic populations to adjust for complex sampling design features.

PubMed

Dong, Qi; Elliott, Michael R; Raghunathan, Trivellore E

2014-06-01

Outside of the survey sampling literature, samples are often assumed to be generated by a simple random sampling process that produces independent and identically distributed (IID) samples. Many statistical methods are developed largely in this IID world. Application of these methods to data from complex sample surveys without making allowance for the survey design features can lead to erroneous inferences. Hence, much time and effort have been devoted to develop the statistical methods to analyze complex survey data and account for the sample design. This issue is particularly important when generating synthetic populations using finite population Bayesian inference, as is often done in missing data or disclosure risk settings, or when combining data from multiple surveys. By extending previous work in finite population Bayesian bootstrap literature, we propose a method to generate synthetic populations from a posterior predictive distribution in a fashion inverts the complex sampling design features and generates simple random samples from a superpopulation point of view, making adjustment on the complex data so that they can be analyzed as simple random samples. We consider a simulation study with a stratified, clustered unequal-probability of selection sample design, and use the proposed nonparametric method to generate synthetic populations for the 2006 National Health Interview Survey (NHIS), and the Medical Expenditure Panel Survey (MEPS), which are stratified, clustered unequal-probability of selection sample designs.

A nonparametric method to generate synthetic populations to adjust for complex sampling design features

PubMed Central

Dong, Qi; Elliott, Michael R.; Raghunathan, Trivellore E.

2017-01-01

Outside of the survey sampling literature, samples are often assumed to be generated by a simple random sampling process that produces independent and identically distributed (IID) samples. Many statistical methods are developed largely in this IID world. Application of these methods to data from complex sample surveys without making allowance for the survey design features can lead to erroneous inferences. Hence, much time and effort have been devoted to develop the statistical methods to analyze complex survey data and account for the sample design. This issue is particularly important when generating synthetic populations using finite population Bayesian inference, as is often done in missing data or disclosure risk settings, or when combining data from multiple surveys. By extending previous work in finite population Bayesian bootstrap literature, we propose a method to generate synthetic populations from a posterior predictive distribution in a fashion inverts the complex sampling design features and generates simple random samples from a superpopulation point of view, making adjustment on the complex data so that they can be analyzed as simple random samples. We consider a simulation study with a stratified, clustered unequal-probability of selection sample design, and use the proposed nonparametric method to generate synthetic populations for the 2006 National Health Interview Survey (NHIS), and the Medical Expenditure Panel Survey (MEPS), which are stratified, clustered unequal-probability of selection sample designs. PMID:29200608

Elder Abuse and Black Americans: Incidence, Correlates, Treatment and Prevention.

ERIC Educational Resources Information Center

Cazenave, Noel A.

Existing evidence on family violence rates by age and race as well as the available data on race and physical elder abuse incidence rates suggests that because such data are not based on random or representative samples and tend to reflect a "sampling artifact" of the particular client populations served by the professionals surveyed,…

The Effect on Non-Normal Distributions on the Integrated Moving Average Model of Time-Series Analysis.

ERIC Educational Resources Information Center

Doerann-George, Judith

The Integrated Moving Average (IMA) model of time series, and the analysis of intervention effects based on it, assume random shocks which are normally distributed. To determine the robustness of the analysis to violations of this assumption, empirical sampling methods were employed. Samples were generated from three populations; normal,…

Implementation of Structured Inquiry Based Model Learning toward Students' Understanding of Geometry

ERIC Educational Resources Information Center

Salim, Kalbin; Tiawa, Dayang Hjh

2015-01-01

The purpose of this study is implementation of a structured inquiry learning model in instruction of geometry. The model used is a model with a quasi-experimental study amounted to two classes of samples selected from the population of the ten classes with cluster random sampling technique. Data collection tool consists of a test item…

Use of Nutritional Information in Canada: National Trends between 2004 and 2008

ERIC Educational Resources Information Center

Goodman, Samantha; Hammond, David; Pillo-Blocka, Francy; Glanville, Theresa; Jenkins, Richard

2011-01-01

Objective: To examine longitudinal trends in use of nutrition information among Canadians. Design: Population-based telephone and Internet surveys. Setting and Participants: Representative samples of Canadian adults recruited with random-digit dialing sampling in 2004 (n = 2,405) and 2006 (n = 2,014) and an online commercial panel in 2008 (n =…

[A comparison of convenience sampling and purposive sampling].

PubMed

Suen, Lee-Jen Wu; Huang, Hui-Man; Lee, Hao-Hsien

2014-06-01

Convenience sampling and purposive sampling are two different sampling methods. This article first explains sampling terms such as target population, accessible population, simple random sampling, intended sample, actual sample, and statistical power analysis. These terms are then used to explain the difference between "convenience sampling" and purposive sampling." Convenience sampling is a non-probabilistic sampling technique applicable to qualitative or quantitative studies, although it is most frequently used in quantitative studies. In convenience samples, subjects more readily accessible to the researcher are more likely to be included. Thus, in quantitative studies, opportunity to participate is not equal for all qualified individuals in the target population and study results are not necessarily generalizable to this population. As in all quantitative studies, increasing the sample size increases the statistical power of the convenience sample. In contrast, purposive sampling is typically used in qualitative studies. Researchers who use this technique carefully select subjects based on study purpose with the expectation that each participant will provide unique and rich information of value to the study. As a result, members of the accessible population are not interchangeable and sample size is determined by data saturation not by statistical power analysis.

Creel survey sampling designs for estimating effort in short-duration Chinook salmon fisheries

USGS Publications Warehouse

McCormick, Joshua L.; Quist, Michael C.; Schill, Daniel J.

2013-01-01

Chinook Salmon Oncorhynchus tshawytscha sport fisheries in the Columbia River basin are commonly monitored using roving creel survey designs and require precise, unbiased catch estimates. The objective of this study was to examine the relative bias and precision of total catch estimates using various sampling designs to estimate angling effort under the assumption that mean catch rate was known. We obtained information on angling populations based on direct visual observations of portions of Chinook Salmon fisheries in three Idaho river systems over a 23-d period. Based on the angling population, Monte Carlo simulations were used to evaluate the properties of effort and catch estimates for each sampling design. All sampling designs evaluated were relatively unbiased. Systematic random sampling (SYS) resulted in the most precise estimates. The SYS and simple random sampling designs had mean square error (MSE) estimates that were generally half of those observed with cluster sampling designs. The SYS design was more efficient (i.e., higher accuracy per unit cost) than a two-cluster design. Increasing the number of clusters available for sampling within a day decreased the MSE of estimates of daily angling effort, but the MSE of total catch estimates was variable depending on the fishery. The results of our simulations provide guidelines on the relative influence of sample sizes and sampling designs on parameters of interest in short-duration Chinook Salmon fisheries.

Geospatial techniques for developing a sampling frame of watersheds across a region

USGS Publications Warehouse

Gresswell, Robert E.; Bateman, Douglas S.; Lienkaemper, George; Guy, T.J.

2004-01-01

Current land-management decisions that affect the persistence of native salmonids are often influenced by studies of individual sites that are selected based on judgment and convenience. Although this approach is useful for some purposes, extrapolating results to areas that were not sampled is statistically inappropriate because the sampling design is usually biased. Therefore, in recent investigations of coastal cutthroat trout (Oncorhynchus clarki clarki) located above natural barriers to anadromous salmonids, we used a methodology for extending the statistical scope of inference. The purpose of this paper is to apply geospatial tools to identify a population of watersheds and develop a probability-based sampling design for coastal cutthroat trout in western Oregon, USA. The population of mid-size watersheds (500-5800 ha) west of the Cascade Range divide was derived from watershed delineations based on digital elevation models. Because a database with locations of isolated populations of coastal cutthroat trout did not exist, a sampling frame of isolated watersheds containing cutthroat trout had to be developed. After the sampling frame of watersheds was established, isolated watersheds with coastal cutthroat trout were stratified by ecoregion and erosion potential based on dominant bedrock lithology (i.e., sedimentary and igneous). A stratified random sample of 60 watersheds was selected with proportional allocation in each stratum. By comparing watershed drainage areas of streams in the general population to those in the sampling frame and the resulting sample (n = 60), we were able to evaluate the how representative the subset of watersheds was in relation to the population of watersheds. Geospatial tools provided a relatively inexpensive means to generate the information necessary to develop a statistically robust, probability-based sampling design.

Coupling Financial Incentives With Direct Mail in Population-Based Practice.

PubMed

Slater, Jonathan S; Parks, Michael J; Malone, Michael E; Henly, George A; Nelson, Christina L

2017-02-01

Financial incentives are being used increasingly to encourage a wide array of health behaviors because of their well-established efficacy. However, little is known about how to translate incentive-based strategies to public health practice geared toward improving population-level health, and a dearth of research exists on how individuals respond to incentives through public health communication strategies such as direct mail. This study reports results of a population-based randomized controlled trial testing a direct mail, incentive-based intervention for promoting mammography uptake. The study population was composed of a random sample of Minnesota women enrolled in Medicare fee-for-service and overdue for breast cancer screening. Participants ( N = 18,939) were randomized into three groups: (1) Direct Mail only, (2) Direct Mail plus Incentive, and (3) Control. Both direct mail groups received two mailers with a message about the importance of mammography; however, Mail plus Incentive mailers also offered a $25 incentive for getting a mammogram. Logistic regression analyses measured intervention effects. Results showed the odds for receiving mammography were significantly higher for the Direct Mail plus Incentive group compared with both Direct Mail only and Control groups. The use of incentives also proved to be cost-effective. Additionally, the Direct Mail only group was more likely to receive mammography than the Control group. Findings offer experimental evidence on how the population-based strategy of direct mail coupled with a financial incentive can encourage healthy behavior, as well as how incentive-based programs can be translated into health promotion practice aimed at achieving population-level impact.

ADAPTIVE MATCHING IN RANDOMIZED TRIALS AND OBSERVATIONAL STUDIES

PubMed Central

van der Laan, Mark J.; Balzer, Laura B.; Petersen, Maya L.

2014-01-01

SUMMARY In many randomized and observational studies the allocation of treatment among a sample of n independent and identically distributed units is a function of the covariates of all sampled units. As a result, the treatment labels among the units are possibly dependent, complicating estimation and posing challenges for statistical inference. For example, cluster randomized trials frequently sample communities from some target population, construct matched pairs of communities from those included in the sample based on some metric of similarity in baseline community characteristics, and then randomly allocate a treatment and a control intervention within each matched pair. In this case, the observed data can neither be represented as the realization of n independent random variables, nor, contrary to current practice, as the realization of n/2 independent random variables (treating the matched pair as the independent sampling unit). In this paper we study estimation of the average causal effect of a treatment under experimental designs in which treatment allocation potentially depends on the pre-intervention covariates of all units included in the sample. We define efficient targeted minimum loss based estimators for this general design, present a theorem that establishes the desired asymptotic normality of these estimators and allows for asymptotically valid statistical inference, and discuss implementation of these estimators. We further investigate the relative asymptotic efficiency of this design compared with a design in which unit-specific treatment assignment depends only on the units’ covariates. Our findings have practical implications for the optimal design and analysis of pair matched cluster randomized trials, as well as for observational studies in which treatment decisions may depend on characteristics of the entire sample. PMID:25097298

The Association between Childhood and Adolescent Sexual Abuse and Proxies for Sexual Risk Behavior: A Random Sample of the General Population of Sweden

ERIC Educational Resources Information Center

Steel, Jennifer L.; Herlitz, Claes A.

2005-01-01

Objective: Several studies with small and ''high risk'' samples have demonstrated that a history of childhood or adolescent sexual abuse (CASA) is associated with sexual risk behaviors (SRBs). However, few studies with large random samples from the general population have specifically examined the relationship between CASA and SRBs with a…

Misrepresenting random sampling? A systematic review of research papers in the Journal of Advanced Nursing.

PubMed

Williamson, Graham R

2003-11-01

This paper discusses the theoretical limitations of the use of random sampling and probability theory in the production of a significance level (or P-value) in nursing research. Potential alternatives, in the form of randomization tests, are proposed. Research papers in nursing, medicine and psychology frequently misrepresent their statistical findings, as the P-values reported assume random sampling. In this systematic review of studies published between January 1995 and June 2002 in the Journal of Advanced Nursing, 89 (68%) studies broke this assumption because they used convenience samples or entire populations. As a result, some of the findings may be questionable. The key ideas of random sampling and probability theory for statistical testing (for generating a P-value) are outlined. The result of a systematic review of research papers published in the Journal of Advanced Nursing is then presented, showing how frequently random sampling appears to have been misrepresented. Useful alternative techniques that might overcome these limitations are then discussed. REVIEW LIMITATIONS: This review is limited in scope because it is applied to one journal, and so the findings cannot be generalized to other nursing journals or to nursing research in general. However, it is possible that other nursing journals are also publishing research articles based on the misrepresentation of random sampling. The review is also limited because in several of the articles the sampling method was not completely clearly stated, and in this circumstance a judgment has been made as to the sampling method employed, based on the indications given by author(s). Quantitative researchers in nursing should be very careful that the statistical techniques they use are appropriate for the design and sampling methods of their studies. If the techniques they employ are not appropriate, they run the risk of misinterpreting findings by using inappropriate, unrepresentative and biased samples.

Children Without Homes: An Examination of Public Responsibility to Children in Out-of-Home Care.

ERIC Educational Resources Information Center

Knitzer, Jane; And Others

This book is the seventh Children's Defense Fund report on major problems facing American children at risk of placement or already placed out of their homes. The findings are based on a survey of child welfare and probation offices in a stratified random sample of 140 counties (27 with populations over 300,000, and 113 with populations under…

The 'number needed to sample' in primary care research. Comparison of two primary care sampling frames for chronic back pain.

PubMed

Smith, Blair H; Hannaford, Philip C; Elliott, Alison M; Smith, W Cairns; Chambers, W Alastair

2005-04-01

Sampling for primary care research must strike a balance between efficiency and external validity. For most conditions, even a large population sample will yield a small number of cases, yet other sampling techniques risk problems with extrapolation of findings. To compare the efficiency and external validity of two sampling methods for both an intervention study and epidemiological research in primary care--a convenience sample and a general population sample--comparing the response and follow-up rates, the demographic and clinical characteristics of each sample, and calculating the 'number needed to sample' (NNS) for a hypothetical randomized controlled trial. In 1996, we selected two random samples of adults from 29 general practices in Grampian, for an epidemiological study of chronic pain. One sample of 4175 was identified by an electronic questionnaire that listed patients receiving regular analgesic prescriptions--the 'repeat prescription sample'. The other sample of 5036 was identified from all patients on practice lists--the 'general population sample'. Questionnaires, including demographic, pain and general health measures, were sent to all. A similar follow-up questionnaire was sent in 2000 to all those agreeing to participate in further research. We identified a potential group of subjects for a hypothetical trial in primary care based on a recently published trial (those aged 25-64, with severe chronic back pain, willing to participate in further research). The repeat prescription sample produced better response rates than the general sample overall (86% compared with 82%, P < 0.001), from both genders and from the oldest and youngest age groups. The NNS using convenience sampling was 10 for each member of the final potential trial sample, compared with 55 using general population sampling. There were important differences between the samples in age, marital and employment status, social class and educational level. However, among the potential trial sample, there were no demographic differences. Those from the repeat prescription sample had poorer indices than the general population sample in all pain and health measures. The repeat prescription sampling method was approximately five times more efficient than the general population method. However demographic and clinical differences in the repeat prescription sample might hamper extrapolation of findings to the general population, particularly in an epidemiological study, and demonstrate that simple comparison with age and gender of the target population is insufficient.

Precision of systematic and random sampling in clustered populations: habitat patches and aggregating organisms.

PubMed

McGarvey, Richard; Burch, Paul; Matthews, Janet M

2016-01-01

Natural populations of plants and animals spatially cluster because (1) suitable habitat is patchy, and (2) within suitable habitat, individuals aggregate further into clusters of higher density. We compare the precision of random and systematic field sampling survey designs under these two processes of species clustering. Second, we evaluate the performance of 13 estimators for the variance of the sample mean from a systematic survey. Replicated simulated surveys, as counts from 100 transects, allocated either randomly or systematically within the study region, were used to estimate population density in six spatial point populations including habitat patches and Matérn circular clustered aggregations of organisms, together and in combination. The standard one-start aligned systematic survey design, a uniform 10 x 10 grid of transects, was much more precise. Variances of the 10 000 replicated systematic survey mean densities were one-third to one-fifth of those from randomly allocated transects, implying transect sample sizes giving equivalent precision by random survey would need to be three to five times larger. Organisms being restricted to patches of habitat was alone sufficient to yield this precision advantage for the systematic design. But this improved precision for systematic sampling in clustered populations is underestimated by standard variance estimators used to compute confidence intervals. True variance for the survey sample mean was computed from the variance of 10 000 simulated survey mean estimates. Testing 10 published and three newly proposed variance estimators, the two variance estimators (v) that corrected for inter-transect correlation (ν₈ and ν(W)) were the most accurate and also the most precise in clustered populations. These greatly outperformed the two "post-stratification" variance estimators (ν₂ and ν₃) that are now more commonly applied in systematic surveys. Similar variance estimator performance rankings were found with a second differently generated set of spatial point populations, ν₈ and ν(W) again being the best performers in the longer-range autocorrelated populations. However, no systematic variance estimators tested were free from bias. On balance, systematic designs bring more narrow confidence intervals in clustered populations, while random designs permit unbiased estimates of (often wider) confidence interval. The search continues for better estimators of sampling variance for the systematic survey mean.

Sleep Complaints in the Adult Brazilian Population: A National Survey Based on Screening Questions

PubMed Central

Bittencourt, Lia Rita A.; Santos-Silva, Rogerio; Taddei, Jose A.; Andersen, Monica L.; de Mello, Marco T.; Tufik, Sergio

2009-01-01

Study Objectives: The aim of the current survey was to investigate the prevalence of sleep complaints in a randomized cluster sample of the Brazilian population. Methods: A 3-stage cluster sampling technique was utilized to randomly select Brazilian subjects older than 16 years, of both genders and all socioeconomic classes. The final sample of 2,110 subjects from 150 different cities was enough to estimate prevalence in the Brazilian population with a sampling error of ± 2%. Questions about sleep complaints were administered face-to-face by Instituto Datafolha interviewers on March 26 and 27, 2008. Data were expanded using a weighted variable. Results: Of all interviewed subjects, 63% reported at least one sleep related complaint. Sleep complaint prevalence increased with age and was similar among inhabitants of different Brazilian regions, as well as between metropolitan areas and smaller cities. Insomnia and nightmares were significantly more prevalent in women (40% and 25%, respectively), and snoring was more prevalent in men (35%). For sleep complaints with frequencies greater than 3 times per week, we found the following prevalence: 61% for snoring, 35% for insomnia, 17% for nightmares, 53% for leg kicking, and 37% for breathing pauses. Conclusions: Because sleep disorders are affect a high proportion of the population and are known to be correlated with decreased well-being and productivity, more detailed national surveys are necessary to provide relevant information to develop approaches to prevention and treatment. Citation: Bittencourt LRA; Santos-Silva R; Taddei JA; Andersen ML; de Mello MT; Tufik S. Sleep complaints in the adult brazilian population: a national survey based on screening questions. J Clin Sleep Med 2009;5(5):459-463. PMID:19961032

Estimation of population mean in the presence of measurement error and non response under stratified random sampling

PubMed Central

Shabbir, Javid

2018-01-01

In the present paper we propose an improved class of estimators in the presence of measurement error and non-response under stratified random sampling for estimating the finite population mean. The theoretical and numerical studies reveal that the proposed class of estimators performs better than other existing estimators. PMID:29401519

Bias, Confounding, and Interaction: Lions and Tigers, and Bears, Oh My!

PubMed

Vetter, Thomas R; Mascha, Edward J

2017-09-01

Epidemiologists seek to make a valid inference about the causal effect between an exposure and a disease in a specific population, using representative sample data from a specific population. Clinical researchers likewise seek to make a valid inference about the association between an intervention and outcome(s) in a specific population, based upon their randomly collected, representative sample data. Both do so by using the available data about the sample variable to make a valid estimate about its corresponding or underlying, but unknown population parameter. Random error in an experiment can be due to the natural, periodic fluctuation or variation in the accuracy or precision of virtually any data sampling technique or health measurement tool or scale. In a clinical research study, random error can be due to not only innate human variability but also purely chance. Systematic error in an experiment arises from an innate flaw in the data sampling technique or measurement instrument. In the clinical research setting, systematic error is more commonly referred to as systematic bias. The most commonly encountered types of bias in anesthesia, perioperative, critical care, and pain medicine research include recall bias, observational bias (Hawthorne effect), attrition bias, misclassification or informational bias, and selection bias. A confounding variable is a factor associated with both the exposure of interest and the outcome of interest. A confounding variable (confounding factor or confounder) is a variable that correlates (positively or negatively) with both the exposure and outcome. Confounding is typically not an issue in a randomized trial because the randomized groups are sufficiently balanced on all potential confounding variables, both observed and nonobserved. However, confounding can be a major problem with any observational (nonrandomized) study. Ignoring confounding in an observational study will often result in a "distorted" or incorrect estimate of the association or treatment effect. Interaction among variables, also known as effect modification, exists when the effect of 1 explanatory variable on the outcome depends on the particular level or value of another explanatory variable. Bias and confounding are common potential explanations for statistically significant associations between exposure and outcome when the true relationship is noncausal. Understanding interactions is vital to proper interpretation of treatment effects. These complex concepts should be consistently and appropriately considered whenever one is not only designing but also analyzing and interpreting data from a randomized trial or observational study.

Hierarchical model analysis of the Atlantic Flyway Breeding Waterfowl Survey

USGS Publications Warehouse

Sauer, John R.; Zimmerman, Guthrie S.; Klimstra, Jon D.; Link, William A.

2014-01-01

We used log-linear hierarchical models to analyze data from the Atlantic Flyway Breeding Waterfowl Survey. The survey has been conducted by state biologists each year since 1989 in the northeastern United States from Virginia north to New Hampshire and Vermont. Although yearly population estimates from the survey are used by the United States Fish and Wildlife Service for estimating regional waterfowl population status for mallards (Anas platyrhynchos), black ducks (Anas rubripes), wood ducks (Aix sponsa), and Canada geese (Branta canadensis), they are not routinely adjusted to control for time of day effects and other survey design issues. The hierarchical model analysis permits estimation of year effects and population change while accommodating the repeated sampling of plots and controlling for time of day effects in counting. We compared population estimates from the current stratified random sample analysis to population estimates from hierarchical models with alternative model structures that describe year to year changes as random year effects, a trend with random year effects, or year effects modeled as 1-year differences. Patterns of population change from the hierarchical model results generally were similar to the patterns described by stratified random sample estimates, but significant visibility differences occurred between twilight to midday counts in all species. Controlling for the effects of time of day resulted in larger population estimates for all species in the hierarchical model analysis relative to the stratified random sample analysis. The hierarchical models also provided a convenient means of estimating population trend as derived statistics from the analysis. We detected significant declines in mallard and American black ducks and significant increases in wood ducks and Canada geese, a trend that had not been significant for 3 of these 4 species in the prior analysis. We recommend using hierarchical models for analysis of the Atlantic Flyway Breeding Waterfowl Survey.

Scientific Reasoning and Its Relationship with Problem Solving: The Case of Upper Primary Science Teachers

ERIC Educational Resources Information Center

Alshamali, Mahmoud A.; Daher, Wajeeh M.

2016-01-01

This study aimed at identifying the levels of scientific reasoning of upper primary stage (grades 4-7) science teachers based on their use of a problem-solving strategy. The study sample (N = 138; 32 % male and 68 % female) was randomly selected using stratified sampling from an original population of 437 upper primary school teachers. The…

Genetic structure of Mexican Mestizo women with breast cancer based on three STR loci.

PubMed

Calderón-Garcidueñas, Ana L; Rivera-Prieto, Roxana A; Ortíz-Lopez, Rocio; Rivas, Fernando; Barrera-Saldaña, Hugo A; Peñaloza-Espinosa, Rosenda I; Cerda-Flores, Ricardo M

2008-01-01

The aim of this population genetics study was to compare the genetic structure of Mexican women with breast cancer (BrCa) with previously reported data of four random populations (Nuevo León, Hispanics, Chihuahua, and Central Region of Mexico). A sample of 115 unrelated women with BrCa and whose four grandparents were born in five zones of Mexico were interviewed at a reference hospital in Northeastern Mexico. Noncodifying STRs D7S820, D13S317, and D16S39 were analyzed; genotype distribution was in agreement with Hardy-Weinberg expectations for all three markers. Similar allele frequencies among four random populations and this selected population were found. According with this and previous studies using molecular and nonmolecular nuclear DNA markers not associated with any disease, Mexican Mestizo population is genetically homogeneous and therefore, genetic causes of BrCa are less heterogeneous, simplifying genetic epidemiologic studies.

Population impact of a high cardiovascular risk management program delivered by village doctors in rural China: design and rationale of a large, cluster-randomized controlled trial.

PubMed

Yan, Lijing L; Fang, Weigang; Delong, Elizabeth; Neal, Bruce; Peterson, Eric D; Huang, Yining; Sun, Ningling; Yao, Chen; Li, Xian; MacMahon, Stephen; Wu, Yangfeng

2014-04-11

The high-risk strategy has been proven effective in preventing cardiovascular disease; however, the population benefits from these interventions remain unknown. This study aims to assess, at the population level, the effects of an evidence-based high cardiovascular risk management program delivered by village doctors in rural China. The study will employ a cluster-randomized controlled trial in which a total of 120 villages in five northern provinces of China, will be assigned to either intervention (60 villages) or control (60 villages). Village doctors in intervention villages will be trained to implement a simple evidence-based management program designed to identify, treat and follow-up as many as possible individuals at high-risk of cardiovascular disease in the village. The intervention will also include performance feedback as well as a performance-based incentive payment scheme and will last for 2 years. We will draw two different (independent) random samples, before and after the intervention, 20 men aged≥50 years and 20 women aged≥60 years from each village in each sample and a total of 9,600 participants from 2 samples to measure the study outcomes at the population level. The primary outcome will be the pre-post difference in mean systolic blood pressure, analyzed with a generalized estimating equations extension of linear regression model to account for cluster effect. Secondary outcomes will include monthly clinic visits, provision of lifestyle advice, use of antihypertensive medications and use of aspirin. Process and economic evaluations will also be conducted. This trial will be the first implementation trial in the world to evaluate the population impact of the high-risk strategy in prevention and control of cardiovascular disease. The results are expected to provide important information (effectiveness, cost-effectiveness, feasibility and acceptability) to guide policy making for rural China as well as other resource-limited countries. The trial is registered at ClinicalTrials.gov (NCT01259700). Date of initial registration is December 13, 2010.

Influence of Problem Based Learning on Critical Thinking Skills and Competence Class VIII SMPN 1 Gunuang Omeh, 2016/2017

NASA Astrophysics Data System (ADS)

Aswan, D. M.; Lufri, L.; Sumarmin, R.

2018-04-01

This research intends to determine the effect of Problem Based Learning models on students' critical thinking skills and competences. This study was a quasi-experimental research. The population of the study was the students of class VIII SMPN 1 Subdistrict Gunuang Omeh. Random sample selection is done by randomizing the class. Sample class that was chosen VIII3 as an experimental class given that treatment study based on problems and class VIII1 as control class that treatment usually given study. Instrument that used to consist of critical thinking test, cognitive tests, observation sheet of affective and psychomotor. Independent t-test and Mann Whitney U test was used for the analysis. Results showed that there was significant difference (sig <0.05) between control and experimental group. The conclusion of this study was Problem Based Learning models affected the students’ critical thinking skills and competences.

Assessment of Visual Status of the Aeta, a Hunter-Gatherer Population of the Philippines (An AOS Thesis)

PubMed Central

Allingham, R. Rand

2008-01-01

Purpose A screening study was performed to assess levels of visual impairment and blindness among a representative sample of older members of the Aeta, an indigenous hunter-gatherer population living on the island of Luzon in the Philippines. Methods Unrelated older Aeta couples were randomly invited to participate in a visual screening study. All consented individuals had ocular history, medical history, complete ophthalmic examination, height, weight, and blood pressure taken. Results A total of 225 individuals were screened from 4 villages. Visual acuity, both uncorrected and pinhole corrected, was significantly worse among older vs younger age-groups for women, men, and when combined (P < .001). Visual impairment was present in 48% of uncorrected and 43% of pinhole corrected eyes in the oldest age-group. Six percent of the screened population was bilaterally blind. The major causes of blindness were readily treatable. The most common etiologies as a proportion of blind eyes were cataract (66%), refractive error (20%), and trauma (7%). No cases of primary open-angle, primary angle-closure, or exfoliation glaucoma were observed in this population. Discussion Visual impairment and blindness were common in the Aeta population. Primary forms of glaucoma, a major cause of blindness found in most population-based studies, were not observed. The absence of primary glaucoma in this population may reflect random sampling error. However, based on similar findings in the Australian Aborigine, this raises the possibility that these two similar populations may share genetic and/or environmental factors that are protective for glaucoma.. PMID:19277240

Multiple Imputation in Two-Stage Cluster Samples Using The Weighted Finite Population Bayesian Bootstrap.

PubMed

Zhou, Hanzhi; Elliott, Michael R; Raghunathan, Trivellore E

2016-06-01

Multistage sampling is often employed in survey samples for cost and convenience. However, accounting for clustering features when generating datasets for multiple imputation is a nontrivial task, particularly when, as is often the case, cluster sampling is accompanied by unequal probabilities of selection, necessitating case weights. Thus, multiple imputation often ignores complex sample designs and assumes simple random sampling when generating imputations, even though failing to account for complex sample design features is known to yield biased estimates and confidence intervals that have incorrect nominal coverage. In this article, we extend a recently developed, weighted, finite-population Bayesian bootstrap procedure to generate synthetic populations conditional on complex sample design data that can be treated as simple random samples at the imputation stage, obviating the need to directly model design features for imputation. We develop two forms of this method: one where the probabilities of selection are known at the first and second stages of the design, and the other, more common in public use files, where only the final weight based on the product of the two probabilities is known. We show that this method has advantages in terms of bias, mean square error, and coverage properties over methods where sample designs are ignored, with little loss in efficiency, even when compared with correct fully parametric models. An application is made using the National Automotive Sampling System Crashworthiness Data System, a multistage, unequal probability sample of U.S. passenger vehicle crashes, which suffers from a substantial amount of missing data in "Delta-V," a key crash severity measure.

Multiple Imputation in Two-Stage Cluster Samples Using The Weighted Finite Population Bayesian Bootstrap

PubMed Central

Zhou, Hanzhi; Elliott, Michael R.; Raghunathan, Trivellore E.

2017-01-01

Multistage sampling is often employed in survey samples for cost and convenience. However, accounting for clustering features when generating datasets for multiple imputation is a nontrivial task, particularly when, as is often the case, cluster sampling is accompanied by unequal probabilities of selection, necessitating case weights. Thus, multiple imputation often ignores complex sample designs and assumes simple random sampling when generating imputations, even though failing to account for complex sample design features is known to yield biased estimates and confidence intervals that have incorrect nominal coverage. In this article, we extend a recently developed, weighted, finite-population Bayesian bootstrap procedure to generate synthetic populations conditional on complex sample design data that can be treated as simple random samples at the imputation stage, obviating the need to directly model design features for imputation. We develop two forms of this method: one where the probabilities of selection are known at the first and second stages of the design, and the other, more common in public use files, where only the final weight based on the product of the two probabilities is known. We show that this method has advantages in terms of bias, mean square error, and coverage properties over methods where sample designs are ignored, with little loss in efficiency, even when compared with correct fully parametric models. An application is made using the National Automotive Sampling System Crashworthiness Data System, a multistage, unequal probability sample of U.S. passenger vehicle crashes, which suffers from a substantial amount of missing data in “Delta-V,” a key crash severity measure. PMID:29226161

Post-traumatic stress disorder in older adults: a systematic review of the psychotherapy treatment literature.

PubMed

Dinnen, Stephanie; Simiola, Vanessa; Cook, Joan M

2015-01-01

Older adults represent the fastest growing segment of the US and industrialized populations. However, older adults have generally not been included in randomized clinical trials of psychotherapy for post-traumatic stress disorder (PTSD). This review examined reports of psychological treatment for trauma-related problems, primarily PTSD, in studies with samples of at least 50% adults aged 55 and older using standardized measures. A systematic review of the literature was conducted on psychotherapy for PTSD with older adults using PubMed, Medline, PsychInfo, CINAHL, PILOTS, and Google Scholar. A total of 42 studies were retrieved for full review; 22 were excluded because they did not provide at least one outcome measure or results were not reported by age in the case of mixed-age samples. Of the 20 studies that met review criteria, there were: 13 case studies or series, three uncontrolled pilot studies, two randomized clinical trials, one non-randomized concurrent control study and one post hoc effectiveness study. Significant methodological limitations in the current older adult PTSD treatment outcome literature were found reducing its internal validity and generalizability, including non-randomized research designs, lack of comparison conditions and small sample sizes. Select evidence-based interventions validated in younger and middle-aged populations appear acceptable and efficacious with older adults. There are few treatment studies on subsets of the older adult population including cultural and ethnic minorities, women, the oldest old (over 85), and those who are cognitively impaired. Implications for clinical practice and future research directions are discussed.

Experimental design and efficient parameter estimation in preclinical pharmacokinetic studies.

PubMed

Ette, E I; Howie, C A; Kelman, A W; Whiting, B

1995-05-01

Monte Carlo simulation technique used to evaluate the effect of the arrangement of concentrations on the efficiency of estimation of population pharmacokinetic parameters in the preclinical setting is described. Although the simulations were restricted to the one compartment model with intravenous bolus input, they provide the basis of discussing some structural aspects involved in designing a destructive ("quantic") preclinical population pharmacokinetic study with a fixed sample size as is usually the case in such studies. The efficiency of parameter estimation obtained with sampling strategies based on the three and four time point designs were evaluated in terms of the percent prediction error, design number, individual and joint confidence intervals coverage for parameter estimates approaches, and correlation analysis. The data sets contained random terms for both inter- and residual intra-animal variability. The results showed that the typical population parameter estimates for clearance and volume were efficiently (accurately and precisely) estimated for both designs, while interanimal variability (the only random effect parameter that could be estimated) was inefficiently (inaccurately and imprecisely) estimated with most sampling schedules of the two designs. The exact location of the third and fourth time point for the three and four time point designs, respectively, was not critical to the efficiency of overall estimation of all population parameters of the model. However, some individual population pharmacokinetic parameters were sensitive to the location of these times.

Bounce Back Now! Protocol of a population-based randomized controlled trial to examine the efficacy of a Web-based intervention with disaster-affected families.

PubMed

Ruggiero, Kenneth J; Davidson, Tatiana M; McCauley, Jenna; Gros, Kirstin Stauffacher; Welsh, Kyleen; Price, Matthew; Resnick, Heidi S; Danielson, Carla Kmett; Soltis, Kathryn; Galea, Sandro; Kilpatrick, Dean G; Saunders, Benjamin E; Nissenboim, Josh; Muzzy, Wendy; Fleeman, Anna; Amstadter, Ananda B

2015-01-01

Disasters have far-reaching and potentially long-lasting effects on youth and families. Research has consistently shown a clear increase in the prevalence of several mental health disorders after disasters, including depression and posttraumatic stress disorder. Widely accessible evidence-based interventions are needed to address this unmet need for youth and families, who are underrepresented in disaster research. Rapid growth in Internet and Smartphone access, as well as several Web based evaluation studies with various adult populations has shown that Web-based interventions are likely to be feasible in this context and can improve clinical outcomes. Such interventions also are generally cost-effective, can be targeted or personalized, and can easily be integrated in a stepped care approach to screening and intervention delivery. This is a protocol paper that describes an innovative study design in which we evaluate a self-help Web-based resource, Bounce Back Now, with a population-based sample of disaster affected adolescents and families. The paper includes description and justification for sampling selection and procedures, selection of assessment measures and methods, design of the intervention, and statistical evaluation of critical outcomes. Unique features of this study design include the use of address-based sampling to recruit a population-based sample of disaster-affected adolescents and parents, telephone and Web-based assessments, and development and evaluation of a highly individualized Web intervention for adolescents. Challenges related to large-scale evaluation of technology-delivered interventions with high-risk samples in time-sensitive research are discussed, as well as implications for future research and practice. Published by Elsevier Inc.

Bounce Back Now! Protocol of a Population-Based Randomized Controlled Trial to Examine the Efficacy of a Web-based Intervention with Disaster-Affected Families

PubMed Central

Ruggiero, Kenneth J.; Davidson, Tatiana M.; McCauley, Jenna; Gros, Kirstin Stauffacher; Welsh, Kyleen; Price, Matthew; Resnick, Heidi S.; Danielson, Carla Kmett; Soltis, Kathryn; Galea, Sandro; Kilpatrick, Dean G.; Saunders, Benjamin E.; Nissenboim, Josh; Muzzy, Wendy; Fleeman, Anna; Amstadter, Ananda B.

2014-01-01

Disasters have far-reaching and potentially long-lasting effects on youth and families. Research has consistently shown a clear increase in the prevalence of several mental health disorders after disasters, including depression and posttraumatic stress disorder. Widely accessible evidence-based interventions are needed to address this unmet need for youth and families, who are underrepresented in disaster research. Rapid growth in Internet and Smartphone access, as well as several web based evaluation studies with various adult populations has shown that web-based interventions are likely to be feasible in this context and can improve clinical outcomes. Such interventions also are generally cost-effective, can be targeted or personalized, and can easily be integrated in a stepped care approach to screening and intervention delivery. This is a protocol paper that describes an innovative study design in which we evaluate a self-help web-based resource, Bounce Back Now, with a population-based sample of disaster affected adolescents and families. The paper includes description and justification for sampling selection and procedures, selection of assessment measures and methods, design of the intervention, and statistical evaluation of critical outcomes. Unique features of this study design include the use of address-based sampling to recruit a population-based sample of disaster-affected adolescents and parents, telephone and web-based assessments, and development and evaluation of a highly individualized web intervention for adolescents. Challenges related to large-scale evaluation of technology-delivered interventions with high-risk samples in time-sensitive research are discussed, as well as implications for future research and practice. PMID:25478956

Prevalence of rosacea in the general population of Germany and Russia - The RISE study.

PubMed

Tan, J; Schöfer, H; Araviiskaia, E; Audibert, F; Kerrouche, N; Berg, M

2016-03-01

There is an unmet need for general population-based epidemiological data on rosacea based on contemporary diagnostic criteria and validated population survey methodology. To evaluate the prevalence of rosacea in the general population of Germany and Russia. General population screening was conducted in 9-10 cities per country to ensure adequate geographic representation. In Part I of this two-phase study, screening of a representative sample of the general population (every fifth person or every fifth door using a fixed-step procedure on a random route sample) was expedited with use of a questionnaire and algorithm based on current diagnostic criteria for rosacea. Of the subjects that screened positive in the initial phase, a randomly selected sample (every third subject) t`hen underwent diagnostic confirmation by a dermatologist in Part II. A total of 3052 and 3013 subjects (aged 18-65 years) were screened in Germany and Russia respectively. Rosacea prevalence was 12.3% [95%CI, 10.2-14.4] in Germany and 5.0% [95%CI, 2.8-7.2] in Russia. The profile of subjects with rosacea (75% women; mean age of 40 years; mainly skin phototype II or III, majority of subjects with sensitive facial skin) and subtype distribution were similar. Overall, 18% of subjects diagnosed with rosacea were aged 18-30 years. Over 80% were not previously diagnosed. Within the previous year, 47.5% of subjects had received no rosacea care and 23.7% had received topical and/or systemic drugs. Over one-third (35% Germany, 43% Russia) of rosacea subjects reported a moderate to severe adverse impact on quality of life. Rosacea is highly prevalent in Germany (12.3%) and Russia (5.0%). The demographic profile of rosacea subjects was similar between countries and the majority were previously undiagnosed. © 2016 The Authors. Journal of the European Academy of Dermatology and Venereology published by John Wiley & Sons Ltd on behalf of European Academy of Dermatology and Venereology.

Sampling designs for HIV molecular epidemiology with application to Honduras.

PubMed

Shepherd, Bryan E; Rossini, Anthony J; Soto, Ramon Jeremias; De Rivera, Ivette Lorenzana; Mullins, James I

2005-11-01

Proper sampling is essential to characterize the molecular epidemiology of human immunodeficiency virus (HIV). HIV sampling frames are difficult to identify, so most studies use convenience samples. We discuss statistically valid and feasible sampling techniques that overcome some of the potential for bias due to convenience sampling and ensure better representation of the study population. We employ a sampling design called stratified cluster sampling. This first divides the population into geographical and/or social strata. Within each stratum, a population of clusters is chosen from groups, locations, or facilities where HIV-positive individuals might be found. Some clusters are randomly selected within strata and individuals are randomly selected within clusters. Variation and cost help determine the number of clusters and the number of individuals within clusters that are to be sampled. We illustrate the approach through a study designed to survey the heterogeneity of subtype B strains in Honduras.

Health indicators: eliminating bias from convenience sampling estimators.

PubMed

Hedt, Bethany L; Pagano, Marcello

2011-02-28

Public health practitioners are often called upon to make inference about a health indicator for a population at large when the sole available information are data gathered from a convenience sample, such as data gathered on visitors to a clinic. These data may be of the highest quality and quite extensive, but the biases inherent in a convenience sample preclude the legitimate use of powerful inferential tools that are usually associated with a random sample. In general, we know nothing about those who do not visit the clinic beyond the fact that they do not visit the clinic. An alternative is to take a random sample of the population. However, we show that this solution would be wasteful if it excluded the use of available information. Hence, we present a simple annealing methodology that combines a relatively small, and presumably far less expensive, random sample with the convenience sample. This allows us to not only take advantage of powerful inferential tools, but also provides more accurate information than that available from just using data from the random sample alone. Copyright © 2011 John Wiley & Sons, Ltd.

Determination of reference values for elevated fasting and random insulin levels and their associations with metabolic risk factors among rural Pakistanis from Sindh Province.

PubMed

Ahmadani, Muhammad Yakoob; Hakeem, Rubina; Fawwad, Asher; Basit, Abdul; Shera, A Samad

2008-06-01

To assess insulin levels and their association with metabolic risk factors (family history of diabetes, abnormal glucose tolerance, hypertension, overweight and android obesity) among a representative group of Pakistan. The study data was taken from the database of a population-based survey conducted in Sindh Province, Pakistan, in 1994 to assess the prevalence of diabetes mellitus and impaired glucose tolerance (IGT). Through stratified random sampling; oral glucose tolerance tests were performed in 967 adults; every fifth sample was estimated for fasting and random (2-hour post-75 gm glucose load) insulin levels. The total number of metabolic risk factors was counted for each subject, and their association with insulin levels studied. Of the 130 subjects, 56.1% were females and 95.4% were Sindhi. The mean age of males and females was 43.84 and 40.61 years, respectively. Family history for diabetes and frequency of overweight had significant positive associations with both fasting and random insulin levels (P < 0.05). Association between hypertension and insulin levels was significant only for random insulin levels, and between android obesity, abnormal glucose tolerance, or male gender and insulin levels only for fasting insulin levels (P < 0.05). Metabolic risk factors had significant positive associations with both fasting (r = 0.351 P = 0.000) as well as random insulin levels (r = 0.364 P = 0.000). This paper provides baseline pioneering information applicable to the Pakistani population. Furthermore, the observations made in this study about differences in association of fasting or random insulin levels with various metabolic risk factors highlight the possibility of using either of them for risk assessment. This finding needs to be assessed in a larger and nationally representative sample.

A New Stratified Sampling Procedure which Decreases Error Estimation of Varroa Mite Number on Sticky Boards.

PubMed

Kretzschmar, A; Durand, E; Maisonnasse, A; Vallon, J; Le Conte, Y

2015-06-01

A new procedure of stratified sampling is proposed in order to establish an accurate estimation of Varroa destructor populations on sticky bottom boards of the hive. It is based on the spatial sampling theory that recommends using regular grid stratification in the case of spatially structured process. The distribution of varroa mites on sticky board being observed as spatially structured, we designed a sampling scheme based on a regular grid with circles centered on each grid element. This new procedure is then compared with a former method using partially random sampling. Relative error improvements are exposed on the basis of a large sample of simulated sticky boards (n=20,000) which provides a complete range of spatial structures, from a random structure to a highly frame driven structure. The improvement of varroa mite number estimation is then measured by the percentage of counts with an error greater than a given level. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Identifying key demographic parameters of a small island-associated population of Indo-Pacific bottlenose dolphins (Reunion, Indian Ocean).

PubMed

Dulau, Violaine; Estrade, Vanessa; Fayan, Jacques

2017-01-01

Photo-identification surveys of Indo-Pacific bottlenose dolphins were conducted from 2009 to 2014 off Reunion Island (55°E33'/21°S07'), in the Indian Ocean. Robust Design models were applied to produce the most reliable estimate of population abundance and survival rate, while accounting for temporary emigration from the survey area (west coast). The sampling scheme consisted of a five-month (June-October) sampling period in each year of the study. The overall population size at Reunion was estimated to be 72 individuals (SE = 6.17, 95%CI = 61-85), based on a random temporary emigration (γ") of 0.096 and a proportion of 0.70 (SE = 0.03) distinct individuals. The annual survival rate was 0.93 (±0.018 SE, 95%CI = 0.886-0.958) and was constant over time and between sexes. Models considering gender groups indicated different movement patterns between males and females. Males showed null or quasi-null temporary emigration (γ" = γ' < 0.01), while females showed a random temporary emigration (γ") of 0.10, suggesting that a small proportion of females was outside the survey area during each primary sampling period. Sex-specific temporary migration patterns were consistent with movement and residency patterns observed in other areas. The Robust Design approach provided an appropriate sampling scheme for deriving island-associated population parameters, while allowing to restrict survey effort both spatially (i.e. west coast only) and temporally (five months per year). Although abundance and survival were stable over the six years, the small population size of fewer than 100 individuals suggested that this population is highly vulnerable. Priority should be given to reducing any potential impact of human activity on the population and its habitat.

Sampling in health geography: reconciling geographical objectives and probabilistic methods. An example of a health survey in Vientiane (Lao PDR)

PubMed Central

Vallée, Julie; Souris, Marc; Fournet, Florence; Bochaton, Audrey; Mobillion, Virginie; Peyronnie, Karine; Salem, Gérard

2007-01-01

Background Geographical objectives and probabilistic methods are difficult to reconcile in a unique health survey. Probabilistic methods focus on individuals to provide estimates of a variable's prevalence with a certain precision, while geographical approaches emphasise the selection of specific areas to study interactions between spatial characteristics and health outcomes. A sample selected from a small number of specific areas creates statistical challenges: the observations are not independent at the local level, and this results in poor statistical validity at the global level. Therefore, it is difficult to construct a sample that is appropriate for both geographical and probability methods. Methods We used a two-stage selection procedure with a first non-random stage of selection of clusters. Instead of randomly selecting clusters, we deliberately chose a group of clusters, which as a whole would contain all the variation in health measures in the population. As there was no health information available before the survey, we selected a priori determinants that can influence the spatial homogeneity of the health characteristics. This method yields a distribution of variables in the sample that closely resembles that in the overall population, something that cannot be guaranteed with randomly-selected clusters, especially if the number of selected clusters is small. In this way, we were able to survey specific areas while minimising design effects and maximising statistical precision. Application We applied this strategy in a health survey carried out in Vientiane, Lao People's Democratic Republic. We selected well-known health determinants with unequal spatial distribution within the city: nationality and literacy. We deliberately selected a combination of clusters whose distribution of nationality and literacy is similar to the distribution in the general population. Conclusion This paper describes the conceptual reasoning behind the construction of the survey sample and shows that it can be advantageous to choose clusters using reasoned hypotheses, based on both probability and geographical approaches, in contrast to a conventional, random cluster selection strategy. PMID:17543100

Sampling in health geography: reconciling geographical objectives and probabilistic methods. An example of a health survey in Vientiane (Lao PDR).

PubMed

Vallée, Julie; Souris, Marc; Fournet, Florence; Bochaton, Audrey; Mobillion, Virginie; Peyronnie, Karine; Salem, Gérard

2007-06-01

Geographical objectives and probabilistic methods are difficult to reconcile in a unique health survey. Probabilistic methods focus on individuals to provide estimates of a variable's prevalence with a certain precision, while geographical approaches emphasise the selection of specific areas to study interactions between spatial characteristics and health outcomes. A sample selected from a small number of specific areas creates statistical challenges: the observations are not independent at the local level, and this results in poor statistical validity at the global level. Therefore, it is difficult to construct a sample that is appropriate for both geographical and probability methods. We used a two-stage selection procedure with a first non-random stage of selection of clusters. Instead of randomly selecting clusters, we deliberately chose a group of clusters, which as a whole would contain all the variation in health measures in the population. As there was no health information available before the survey, we selected a priori determinants that can influence the spatial homogeneity of the health characteristics. This method yields a distribution of variables in the sample that closely resembles that in the overall population, something that cannot be guaranteed with randomly-selected clusters, especially if the number of selected clusters is small. In this way, we were able to survey specific areas while minimising design effects and maximising statistical precision. We applied this strategy in a health survey carried out in Vientiane, Lao People's Democratic Republic. We selected well-known health determinants with unequal spatial distribution within the city: nationality and literacy. We deliberately selected a combination of clusters whose distribution of nationality and literacy is similar to the distribution in the general population. This paper describes the conceptual reasoning behind the construction of the survey sample and shows that it can be advantageous to choose clusters using reasoned hypotheses, based on both probability and geographical approaches, in contrast to a conventional, random cluster selection strategy.

Incidence and seroprevalence of tularaemia in Finland, 1995 to 2013: regional epidemics with cyclic pattern.

PubMed

Rossow, H; Ollgren, J; Hytonen, J; Rissanen, H; Huitu, O; Henttonen, H; Kuusi, M; Vapalahti, O

2015-08-20

We studied the incidence of reported tularaemia by year and region and the prevalence of antibodies against Francisella tularensis in the adult general population in Finland. Moreover, we assessed the correlation between vole population cycles and human tularaemia outbreaks. The seroprevalence study made use of serum samples from a nationwide population-based health survey (Health 2000). The samples of 1,045 randomly selected persons, representative for the Finnish population in each region, were screened with an enzyme-linked immunosorbent assay (ELISA) for the presence of IgG antibodies against F. tularensis, and positive results were further confirmed by immunoblotting. A serological response to F. tularensis was found in 2% (95% confidence interval: 1.1–3.5) of the population. Incidence and seroprevalence were highest in the same areas, and vole population peaks clearly preceded tularaemia outbreaks one year later.

Shared Genetic Influences on Negative Emotionality and Major Depression/Conduct Disorder Comorbidity

ERIC Educational Resources Information Center

Tackett, Jennifer L.; Waldman, Irwin D.; Van Hulle, Carol A.; Lahey, Benjamin B.

2011-01-01

Objective: To investigate whether genetic contributions to major depressive disorder and conduct disorder comorbidity are shared with genetic influences on negative emotionality. Method: Primary caregivers of 2,022 same- and opposite-sex twin pairs 6 to 18 years of age comprised a population-based sample. Participants were randomly selected across…

Nonsuicidal Self-Injury in a College Population: General Trends and Sex Differences

ERIC Educational Resources Information Center

Whitlock, Janis; Muehlenkamp, Jennifer; Purington, Amanda; Eckenrode, John; Barreira, Paul; Abrams, Gina Baral; Marchell, Tim; Kress, Victoria; Girard, Kristine; Chin, Calvin; Knox, Kerry

2011-01-01

Objective: To describe basic nonsuicidal self-injury (NSSI) characteristics and to explore sex differences. Methods: A random sample from 8 universities were invited to participate in a Web-based survey in 2006-2007; 38.9% (n = 14,372) participated. Analysis assessed sex differences in NSSI prevalence, practices, severity, perceived dependency,…

Mitigating budget constraints on visitation volume surveys: the case of U.S. National forests

Treesearch

Ashley E. Askew; Donald B.K. English; Stanley J. Zarnoch; Neelam C. Poudyal; J.M. Bowker

2014-01-01

Stratified random sampling (SRS) provides a scientifically based estimate of a population comprising mutually exclusive, homogenous subgroups. In the National Visitor Use Monitoring (NVUM) program, SRS is used to estimate recreation visitation and visitor characteristics across activities on National forests. However, with rising costs and declining budgets, carrying...

Contaminants in fish tissue from US lakes and reservoirs: A ...

EPA Pesticide Factsheets

An unequal probability design was used to develop national estimates for 268 persistent, bioaccumulative, and toxic chemicals in fish tissue from lakes and reservoirs of the conterminous United States (excluding the Laurentian Great Lakes and Great Salt Lake). Predator (fillet) and bottom-dweller (whole-body) composites were collected from 500 lakes selected randomly from the target population of 147,343 lakes in the lower 48 states. Each of these composite types comprised nationally representative samples whose results were extrapolated to the sampled population of an estimated 76,559 lakes for predators and 46,190 lakes for bottom dwellers. Mercury and PCBs were detected in all fish samples. Dioxins and furans were detected in 81% and 99% of predator and bottom-dweller samples, respectively. Cumulative frequency distributions showed that mercury concentrations exceeded the EPA 300 ppb mercury fish tissue criterion at nearly half of the lakes in the sampled population. Total PCB concentrations exceeded a 12 ppb human health risk-based consumption limit at nearly 17% of lakes, and dioxins and furans exceeded a 0.15 ppt (toxic equivalent or TEQ) risk-based threshold at nearly 8% of lakes in the sampled population. In contrast, 43 target chemicals were not detected in any samples. No detections were reported for nine organophosphate pesticides, one PCB congener, 16 polycyclic aromatic hydrocarbons, or 17 other semivolatile organic chemicals. An unequal prob

Contaminants in fish tissue from US lakes and reservoirs: a national probabilistic study.

PubMed

Stahl, Leanne L; Snyder, Blaine D; Olsen, Anthony R; Pitt, Jennifer L

2009-03-01

An unequal probability design was used to develop national estimates for 268 persistent, bioaccumulative, and toxic chemicals in fish tissue from lakes and reservoirs of the conterminous United States (excluding the Laurentian Great Lakes and Great Salt Lake). Predator (fillet) and bottom-dweller (whole body) composites were collected from 500 lakes selected randomly from the target population of 147,343 lakes in the lower 48 states. Each of these composite types comprised nationally representative samples whose results were extrapolated to the sampled population of an estimated 76,559 lakes for predators and 46,190 lakes for bottom dwellers. Mercury and PCBs were detected in all fish samples. Dioxins and furans were detected in 81% and 99% of predator and bottom-dweller samples, respectively. Cumulative frequency distributions showed that mercury concentrations exceeded the EPA 300 ppb mercury fish tissue criterion at nearly half of the lakes in the sampled population. Total PCB concentrations exceeded a 12 ppb human health risk-based consumption limit at nearly 17% of lakes, and dioxins and furans exceeded a 0.15 ppt (toxic equivalent or TEQ) risk-based threshold at nearly 8% of lakes in the sampled population. In contrast, 43 target chemicals were not detected in any samples. No detections were reported for nine organophosphate pesticides, one PCB congener, 16 polycyclic aromatic hydrocarbons, or 17 other semivolatile organic chemicals.

Repeated Random Sampling in Year 5

ERIC Educational Resources Information Center

Watson, Jane M.; English, Lyn D.

2016-01-01

As an extension to an activity introducing Year 5 students to the practice of statistics, the software "TinkerPlots" made it possible to collect repeated random samples from a finite population to informally explore students' capacity to begin reasoning with a distribution of sample statistics. This article provides background for the…

The Danish National Health Survey 2010. Study design and respondent characteristics.

PubMed

Christensen, Anne Illemann; Ekholm, Ola; Glümer, Charlotte; Andreasen, Anne Helms; Hvidberg, Michael Falk; Kristensen, Peter Lund; Larsen, Finn Breinholt; Ortiz, Britta; Juel, Knud

2012-06-01

In 2010 the five Danish regions and the National Institute of Public Health at the University of Southern Denmark conducted a national representative health survey among the adult population in Denmark. This paper describes the study design and the sample and study population as well as the content of the questionnaire. The survey was based on five regional stratified random samples and one national random sample. The samples were mutually exclusive. A total of 298,550 individuals (16 years or older) were invited to participate. Information was collected using a mixed mode approach (paper and web questionnaires). A questionnaire with a minimum of 52 core questions was used in all six subsamples. Calibrated weights were computed in order to take account of the complex survey design and reduce non-response bias. In all, 177,639 individuals completed the questionnaire (59.5%). The response rate varied from 52.3% in the Capital Region of Denmark sample to 65.5% in the North Denmark Region sample. The response rate was particularly low among young men, unmarried people and among individuals with a different ethnic background than Danish. The survey was a result of extensive national cooperation across sectors, which makes it unique in its field of application, e.g. health surveillance, planning and prioritizing public health initiatives and research. However, the low response rate in some subgroups of the study population can pose problems in generalizing data, and efforts to increase the response rate will be important in the forthcoming surveys.

Accounting for selection bias in association studies with complex survey data.

PubMed

Wirth, Kathleen E; Tchetgen Tchetgen, Eric J

2014-05-01

Obtaining representative information from hidden and hard-to-reach populations is fundamental to describe the epidemiology of many sexually transmitted diseases, including HIV. Unfortunately, simple random sampling is impractical in these settings, as no registry of names exists from which to sample the population at random. However, complex sampling designs can be used, as members of these populations tend to congregate at known locations, which can be enumerated and sampled at random. For example, female sex workers may be found at brothels and street corners, whereas injection drug users often come together at shooting galleries. Despite the logistical appeal, complex sampling schemes lead to unequal probabilities of selection, and failure to account for this differential selection can result in biased estimates of population averages and relative risks. However, standard techniques to account for selection can lead to substantial losses in efficiency. Consequently, researchers implement a variety of strategies in an effort to balance validity and efficiency. Some researchers fully or partially account for the survey design, whereas others do nothing and treat the sample as a realization of the population of interest. We use directed acyclic graphs to show how certain survey sampling designs, combined with subject-matter considerations unique to individual exposure-outcome associations, can induce selection bias. Finally, we present a novel yet simple maximum likelihood approach for analyzing complex survey data; this approach optimizes statistical efficiency at no cost to validity. We use simulated data to illustrate this method and compare it with other analytic techniques.

Marginal bone level in two Danish cross-sectional population samples in 1997-1998 and 2007-2008.

PubMed

Bahrami, Golnosh; Vaeth, Michael; Wenzel, Ann; Isidor, Flemming

2018-04-12

The aim of this study was to compare the marginal bone level of two randomly selected population samples from 1997/1998 and 2007/2008, with special emphasis on the role of smoking habits and gender. Two cross-sectional randomly selected population samples [1997/1998 (N = 616) and 2007/2008 (N = 396)] were analysed with respect to the marginal bone level. The marginal bone level was measured in full-mouth intraoral radiographs. Information on smoking was gathered using questionnaires. Multiple regression analysis was used in order to adjust for correlating factors (gender, age, smoking habits and number of teeth). After adjusting for confounding factors, the population sample from 2007/2008 had on average a slightly, but statistically significantly, more reduced average marginal bone level (0.15 mm) than the population sample from 1997/1998. Men had more reduced marginal bone level than women (0.12 mm). Smokers in both population samples had more reduced marginal bone level than non-smokers (0.39 mm and 0.12 mm for 1997/1998; 0.65 mm and 0.16 mm for 2007/2008). In these populations, sampled 10 years apart, the 2007/2008 population sample had a slightly more reduced marginal bone level than the 1997/1998 population sample. Men had more reduced marginal bone level than women, and smoking is considered a major risk factor for a reduced marginal bone level.

Sampling in epidemiological research: issues, hazards and pitfalls.

PubMed

Tyrer, Stephen; Heyman, Bob

2016-04-01

Surveys of people's opinions are fraught with difficulties. It is easier to obtain information from those who respond to text messages or to emails than to attempt to obtain a representative sample. Samples of the population that are selected non-randomly in this way are termed convenience samples as they are easy to recruit. This introduces a sampling bias. Such non-probability samples have merit in many situations, but an epidemiological enquiry is of little value unless a random sample is obtained. If a sufficient number of those selected actually complete a survey, the results are likely to be representative of the population. This editorial describes probability and non-probability sampling methods and illustrates the difficulties and suggested solutions in performing accurate epidemiological research.

Sampling in epidemiological research: issues, hazards and pitfalls

PubMed Central

Tyrer, Stephen; Heyman, Bob

2016-01-01

Surveys of people's opinions are fraught with difficulties. It is easier to obtain information from those who respond to text messages or to emails than to attempt to obtain a representative sample. Samples of the population that are selected non-randomly in this way are termed convenience samples as they are easy to recruit. This introduces a sampling bias. Such non-probability samples have merit in many situations, but an epidemiological enquiry is of little value unless a random sample is obtained. If a sufficient number of those selected actually complete a survey, the results are likely to be representative of the population. This editorial describes probability and non-probability sampling methods and illustrates the difficulties and suggested solutions in performing accurate epidemiological research. PMID:27087985

Improving Generalizations from Experiments Using Propensity Score Subclassification: Assumptions, Properties, and Contexts

ERIC Educational Resources Information Center

Tipton, Elizabeth

2013-01-01

As a result of the use of random assignment to treatment, randomized experiments typically have high internal validity. However, units are very rarely randomly selected from a well-defined population of interest into an experiment; this results in low external validity. Under nonrandom sampling, this means that the estimate of the sample average…

Effectiveness of Family, Child, and Family-Child Based Intervention on ADHD Symptoms of Students with Disabilities

ERIC Educational Resources Information Center

Malekpour, Mokhtar; Aghababaei, Sara; Hadi, Samira

2014-01-01

The aim of the present study was to investigate and compare the effectiveness of family, child, and family-child based intervention on the rate of ADHD symptoms in third grade students. The population for this study was all of students with ADHD diagnoses in the city of Isfahan, Iran. The multistage random sampling method was used to select the 60…

Knowledge and attitude towards total knee arthroplasty among the public in Saudi Arabia: a nationwide population-based study.

PubMed

Al-Mohrej, Omar A; Alshammari, Faris O; Aljuraisi, Abdulrahman M; Bin Amer, Lujain A; Masuadi, Emad M; Al-Kenani, Nader S

2018-04-01

Studies on total knee arthroplasty (TKA) in Saudi Arabia are scarce, and none have reported the knowledge and attitude of the procedure in Saudi Arabia. Our study aims to measure the knowledge and attitude of TKA among the adult Saudi population. To encompass a representative sample of this cross-sectional survey, all 13 administrative areas were used as ready-made geographical clusters. For each cluster, stratified random sampling was performed to maximize participation in the study. In each area, random samples of mobile phone numbers were selected with a probability proportional to the administrative area population size. Sample size calculation was based on the assumption that 50% of the participants would have some level of knowledge, with a 2% margin of error and 95% confidence level. To reach our intended sample size of 1540, we contacted 1722 participants with a response rate of 89.4%. The expected percentage of public knowledge was 50%; however, the actual percentage revealed by this study was much lower (29.7%). A stepwise multiple logistic regression was used to assess the factors that positively affected the knowledge score regarding TKA. Age [P = 0.016 with OR of 0.47], higher income [P = 0.001 with OR of 0.52] and participants with a positive history of TKA or that have known someone who underwent the surgery [P < 0.001 with OR of 0.15] had a positive impact on the total knowledge score. There are still misconceptions among the public in Saudi Arabia concerning TKA, its indications and results. We recommend that doctors use the results of our survey to assess their conversations with their patients, and to determine whether the results of the procedure are adequately clarified.

A Statistical Method to Distinguish Functional Brain Networks

PubMed Central

Fujita, André; Vidal, Maciel C.; Takahashi, Daniel Y.

2017-01-01

One major problem in neuroscience is the comparison of functional brain networks of different populations, e.g., distinguishing the networks of controls and patients. Traditional algorithms are based on search for isomorphism between networks, assuming that they are deterministic. However, biological networks present randomness that cannot be well modeled by those algorithms. For instance, functional brain networks of distinct subjects of the same population can be different due to individual characteristics. Moreover, networks of subjects from different populations can be generated through the same stochastic process. Thus, a better hypothesis is that networks are generated by random processes. In this case, subjects from the same group are samples from the same random process, whereas subjects from different groups are generated by distinct processes. Using this idea, we developed a statistical test called ANOGVA to test whether two or more populations of graphs are generated by the same random graph model. Our simulations' results demonstrate that we can precisely control the rate of false positives and that the test is powerful to discriminate random graphs generated by different models and parameters. The method also showed to be robust for unbalanced data. As an example, we applied ANOGVA to an fMRI dataset composed of controls and patients diagnosed with autism or Asperger. ANOGVA identified the cerebellar functional sub-network as statistically different between controls and autism (p < 0.001). PMID:28261045

A Statistical Method to Distinguish Functional Brain Networks.

PubMed

Fujita, André; Vidal, Maciel C; Takahashi, Daniel Y

2017-01-01

One major problem in neuroscience is the comparison of functional brain networks of different populations, e.g., distinguishing the networks of controls and patients. Traditional algorithms are based on search for isomorphism between networks, assuming that they are deterministic. However, biological networks present randomness that cannot be well modeled by those algorithms. For instance, functional brain networks of distinct subjects of the same population can be different due to individual characteristics. Moreover, networks of subjects from different populations can be generated through the same stochastic process. Thus, a better hypothesis is that networks are generated by random processes. In this case, subjects from the same group are samples from the same random process, whereas subjects from different groups are generated by distinct processes. Using this idea, we developed a statistical test called ANOGVA to test whether two or more populations of graphs are generated by the same random graph model. Our simulations' results demonstrate that we can precisely control the rate of false positives and that the test is powerful to discriminate random graphs generated by different models and parameters. The method also showed to be robust for unbalanced data. As an example, we applied ANOGVA to an fMRI dataset composed of controls and patients diagnosed with autism or Asperger. ANOGVA identified the cerebellar functional sub-network as statistically different between controls and autism ( p < 0.001).

Estimation of infection prevalence and sensitivity in a stratified two-stage sampling design employing highly specific diagnostic tests when there is no gold standard.

PubMed

Miller, Ezer; Huppert, Amit; Novikov, Ilya; Warburg, Alon; Hailu, Asrat; Abbasi, Ibrahim; Freedman, Laurence S

2015-11-10

In this work, we describe a two-stage sampling design to estimate the infection prevalence in a population. In the first stage, an imperfect diagnostic test was performed on a random sample of the population. In the second stage, a different imperfect test was performed in a stratified random sample of the first sample. To estimate infection prevalence, we assumed conditional independence between the diagnostic tests and develop method of moments estimators based on expectations of the proportions of people with positive and negative results on both tests that are functions of the tests' sensitivity, specificity, and the infection prevalence. A closed-form solution of the estimating equations was obtained assuming a specificity of 100% for both tests. We applied our method to estimate the infection prevalence of visceral leishmaniasis according to two quantitative polymerase chain reaction tests performed on blood samples taken from 4756 patients in northern Ethiopia. The sensitivities of the tests were also estimated, as well as the standard errors of all estimates, using a parametric bootstrap. We also examined the impact of departures from our assumptions of 100% specificity and conditional independence on the estimated prevalence. Copyright © 2015 John Wiley & Sons, Ltd.

The efficacy of respondent-driven sampling for the health assessment of minority populations.

PubMed

Badowski, Grazyna; Somera, Lilnabeth P; Simsiman, Brayan; Lee, Hye-Ryeon; Cassel, Kevin; Yamanaka, Alisha; Ren, JunHao

2017-10-01

Respondent driven sampling (RDS) is a relatively new network sampling technique typically employed for hard-to-reach populations. Like snowball sampling, initial respondents or "seeds" recruit additional respondents from their network of friends. Under certain assumptions, the method promises to produce a sample independent from the biases that may have been introduced by the non-random choice of "seeds." We conducted a survey on health communication in Guam's general population using the RDS method, the first survey that has utilized this methodology in Guam. It was conducted in hopes of identifying a cost-efficient non-probability sampling strategy that could generate reasonable population estimates for both minority and general populations. RDS data was collected in Guam in 2013 (n=511) and population estimates were compared with 2012 BRFSS data (n=2031) and the 2010 census data. The estimates were calculated using the unweighted RDS sample and the weighted sample using RDS inference methods and compared with known population characteristics. The sample size was reached in 23days, providing evidence that the RDS method is a viable, cost-effective data collection method, which can provide reasonable population estimates. However, the results also suggest that the RDS inference methods used to reduce bias, based on self-reported estimates of network sizes, may not always work. Caution is needed when interpreting RDS study findings. For a more diverse sample, data collection should not be conducted in just one location. Fewer questions about network estimates should be asked, and more careful consideration should be given to the kind of incentives offered to participants. Copyright © 2017. Published by Elsevier Ltd.

Ant-inspired density estimation via random walks.

PubMed

Musco, Cameron; Su, Hsin-Hao; Lynch, Nancy A

2017-10-03

Many ant species use distributed population density estimation in applications ranging from quorum sensing, to task allocation, to appraisal of enemy colony strength. It has been shown that ants estimate local population density by tracking encounter rates: The higher the density, the more often the ants bump into each other. We study distributed density estimation from a theoretical perspective. We prove that a group of anonymous agents randomly walking on a grid are able to estimate their density within a small multiplicative error in few steps by measuring their rates of encounter with other agents. Despite dependencies inherent in the fact that nearby agents may collide repeatedly (and, worse, cannot recognize when this happens), our bound nearly matches what would be required to estimate density by independently sampling grid locations. From a biological perspective, our work helps shed light on how ants and other social insects can obtain relatively accurate density estimates via encounter rates. From a technical perspective, our analysis provides tools for understanding complex dependencies in the collision probabilities of multiple random walks. We bound the strength of these dependencies using local mixing properties of the underlying graph. Our results extend beyond the grid to more general graphs, and we discuss applications to size estimation for social networks, density estimation for robot swarms, and random walk-based sampling for sensor networks.

A fosmid cloning strategy for detecting the widest possible spectrum of microbes from the international space station drinking water system.

PubMed

Choi, Sangdun; Chang, Mi Sook; Stuecker, Tara; Chung, Christine; Newcombe, David A; Venkateswaran, Kasthuri

2012-12-01

In this study, fosmid cloning strategies were used to assess the microbial populations in water from the International Space Station (ISS) drinking water system (henceforth referred to as Prebiocide and Tank A water samples). The goals of this study were: to compare the sensitivity of the fosmid cloning strategy with that of traditional culture-based and 16S rRNA-based approaches and to detect the widest possible spectrum of microbial populations during the water purification process. Initially, microbes could not be cultivated, and conventional PCR failed to amplify 16S rDNA fragments from these low biomass samples. Therefore, randomly primed rolling-circle amplification was used to amplify any DNA that might be present in the samples, followed by size selection by using pulsed-field gel electrophoresis. The amplified high-molecular-weight DNA from both samples was cloned into fosmid vectors. Several hundred clones were randomly selected for sequencing, followed by Blastn/Blastx searches. Sequences encoding specific genes from Burkholderia, a species abundant in the soil and groundwater, were found in both samples. Bradyrhizobium and Mesorhizobium, which belong to rhizobia, a large community of nitrogen fixers often found in association with plant roots, were present in the Prebiocide samples. Ralstonia, which is prevalent in soils with a high heavy metal content, was detected in the Tank A samples. The detection of many unidentified sequences suggests the presence of potentially novel microbial fingerprints. The bacterial diversity detected in this pilot study using a fosmid vector approach was higher than that detected by conventional 16S rRNA gene sequencing.

Gaussian process-based Bayesian nonparametric inference of population size trajectories from gene genealogies.

PubMed

Palacios, Julia A; Minin, Vladimir N

2013-03-01

Changes in population size influence genetic diversity of the population and, as a result, leave a signature of these changes in individual genomes in the population. We are interested in the inverse problem of reconstructing past population dynamics from genomic data. We start with a standard framework based on the coalescent, a stochastic process that generates genealogies connecting randomly sampled individuals from the population of interest. These genealogies serve as a glue between the population demographic history and genomic sequences. It turns out that only the times of genealogical lineage coalescences contain information about population size dynamics. Viewing these coalescent times as a point process, estimating population size trajectories is equivalent to estimating a conditional intensity of this point process. Therefore, our inverse problem is similar to estimating an inhomogeneous Poisson process intensity function. We demonstrate how recent advances in Gaussian process-based nonparametric inference for Poisson processes can be extended to Bayesian nonparametric estimation of population size dynamics under the coalescent. We compare our Gaussian process (GP) approach to one of the state-of-the-art Gaussian Markov random field (GMRF) methods for estimating population trajectories. Using simulated data, we demonstrate that our method has better accuracy and precision. Next, we analyze two genealogies reconstructed from real sequences of hepatitis C and human Influenza A viruses. In both cases, we recover more believed aspects of the viral demographic histories than the GMRF approach. We also find that our GP method produces more reasonable uncertainty estimates than the GMRF method. Copyright © 2013, The International Biometric Society.

Prevalence of Childhood Sexual Abuse among Incarcerated Males in County Jail

ERIC Educational Resources Information Center

Johnson, Regina J.; Ross, Michael W.; Taylor, Wendell C.; Williams, Mark L.; Carvajal, Raul I.; Peters, Ronald J.

2006-01-01

Objective: The current study examined the prevalence and characteristics of childhood sexual abuse in a jailed-based population. Methodology: A retrospective, self-reported survey was administered over an 8-week period to a random sample of 100 men who were incarcerated in a county jail in Southeastern Texas. The survey included questions about…

The correspondence of surface climate parameters with satellite and terrain data

NASA Technical Reports Server (NTRS)

Dozier, Jeff; Davis, Frank

1987-01-01

One of the goals of the research was to develop a ground sampling stragegy for calibrating remotely sensed measurements of surface climate parameters. The initial sampling strategy involved the stratification of the terrain based on important ancillary surface variables such as slope, exposure, insolation, geology, drainage, fire history, etc. For a spatially heterogeneous population, sampling error is reduced and efficiency increased by stratification of the landscape into more homogeneous sub-areas and by employing periodic random spacing of samples. These concepts were applied in the initial stratification of the study site for the purpose of locating and allocating instrumentation.

Sampling Methods in Cardiovascular Nursing Research: An Overview.

PubMed

Kandola, Damanpreet; Banner, Davina; O'Keefe-McCarthy, Sheila; Jassal, Debbie

2014-01-01

Cardiovascular nursing research covers a wide array of topics from health services to psychosocial patient experiences. The selection of specific participant samples is an important part of the research design and process. The sampling strategy employed is of utmost importance to ensure that a representative sample of participants is chosen. There are two main categories of sampling methods: probability and non-probability. Probability sampling is the random selection of elements from the population, where each element of the population has an equal and independent chance of being included in the sample. There are five main types of probability sampling including simple random sampling, systematic sampling, stratified sampling, cluster sampling, and multi-stage sampling. Non-probability sampling methods are those in which elements are chosen through non-random methods for inclusion into the research study and include convenience sampling, purposive sampling, and snowball sampling. Each approach offers distinct advantages and disadvantages and must be considered critically. In this research column, we provide an introduction to these key sampling techniques and draw on examples from the cardiovascular research. Understanding the differences in sampling techniques may aid nurses in effective appraisal of research literature and provide a reference pointfor nurses who engage in cardiovascular research.

Computerized stratified random site-selection approaches for design of a ground-water-quality sampling network

USGS Publications Warehouse

Scott, J.C.

1990-01-01

Computer software was written to randomly select sites for a ground-water-quality sampling network. The software uses digital cartographic techniques and subroutines from a proprietary geographic information system. The report presents the approaches, computer software, and sample applications. It is often desirable to collect ground-water-quality samples from various areas in a study region that have different values of a spatial characteristic, such as land-use or hydrogeologic setting. A stratified network can be used for testing hypotheses about relations between spatial characteristics and water quality, or for calculating statistical descriptions of water-quality data that account for variations that correspond to the spatial characteristic. In the software described, a study region is subdivided into areal subsets that have a common spatial characteristic to stratify the population into several categories from which sampling sites are selected. Different numbers of sites may be selected from each category of areal subsets. A population of potential sampling sites may be defined by either specifying a fixed population of existing sites, or by preparing an equally spaced population of potential sites. In either case, each site is identified with a single category, depending on the value of the spatial characteristic of the areal subset in which the site is located. Sites are selected from one category at a time. One of two approaches may be used to select sites. Sites may be selected randomly, or the areal subsets in the category can be grouped into cells and sites selected randomly from each cell.

Systematic sampling of discrete and continuous populations: sample selection and the choice of estimator

Treesearch

Harry T. Valentine; David L. R. Affleck; Timothy G. Gregoire

2009-01-01

Systematic sampling is easy, efficient, and widely used, though it is not generally recognized that a systematic sample may be drawn from the population of interest with or without restrictions on randomization. The restrictions or the lack of them determine which estimators are unbiased, when using the sampling design as the basis for inference. We describe the...

Effect of separate sampling on classification accuracy.

PubMed

Shahrokh Esfahani, Mohammad; Dougherty, Edward R

2014-01-15

Measurements are commonly taken from two phenotypes to build a classifier, where the number of data points from each class is predetermined, not random. In this 'separate sampling' scenario, the data cannot be used to estimate the class prior probabilities. Moreover, predetermined class sizes can severely degrade classifier performance, even for large samples. We employ simulations using both synthetic and real data to show the detrimental effect of separate sampling on a variety of classification rules. We establish propositions related to the effect on the expected classifier error owing to a sampling ratio different from the population class ratio. From these we derive a sample-based minimax sampling ratio and provide an algorithm for approximating it from the data. We also extend to arbitrary distributions the classical population-based Anderson linear discriminant analysis minimax sampling ratio derived from the discriminant form of the Bayes classifier. All the codes for synthetic data and real data examples are written in MATLAB. A function called mmratio, whose output is an approximation of the minimax sampling ratio of a given dataset, is also written in MATLAB. All the codes are available at: http://gsp.tamu.edu/Publications/supplementary/shahrokh13b.

Training set optimization under population structure in genomic selection.

PubMed

Isidro, Julio; Jannink, Jean-Luc; Akdemir, Deniz; Poland, Jesse; Heslot, Nicolas; Sorrells, Mark E

2015-01-01

Population structure must be evaluated before optimization of the training set population. Maximizing the phenotypic variance captured by the training set is important for optimal performance. The optimization of the training set (TRS) in genomic selection has received much interest in both animal and plant breeding, because it is critical to the accuracy of the prediction models. In this study, five different TRS sampling algorithms, stratified sampling, mean of the coefficient of determination (CDmean), mean of predictor error variance (PEVmean), stratified CDmean (StratCDmean) and random sampling, were evaluated for prediction accuracy in the presence of different levels of population structure. In the presence of population structure, the most phenotypic variation captured by a sampling method in the TRS is desirable. The wheat dataset showed mild population structure, and CDmean and stratified CDmean methods showed the highest accuracies for all the traits except for test weight and heading date. The rice dataset had strong population structure and the approach based on stratified sampling showed the highest accuracies for all traits. In general, CDmean minimized the relationship between genotypes in the TRS, maximizing the relationship between TRS and the test set. This makes it suitable as an optimization criterion for long-term selection. Our results indicated that the best selection criterion used to optimize the TRS seems to depend on the interaction of trait architecture and population structure.

Prevalence of Latent Mycobacterium Tuberculosis Infection (LTBI) in Saudi Arabia; Population based survey.

PubMed

Balkhy, Hanan H; El Beltagy, Kamel; El-Saed, Aiman; Aljasir, Badr; Althaqafi, Abdulhakeem; Alothman, Adel F; Alshalaan, Mohammad; Al-Jahdali, Hamdan

2017-07-01

The annual risk of tuberculosis infection (ARTI) data in Saudi Arabia has not been updated since 1993. To estimate the prevalence of latent TB infection (LTBI) and ARTI in a population-based sample in Saudi Arabia using Tuberculin skin test (TST) and QuantiFERON TB Gold in tube (QFT-GIT) test. A population-based cross sectional study was conducted between July 2010 and March 2013. Participants were randomly selected from the population served by the primary healthcare centers of the Ministry of National Guard Health Affairs in Riyadh, Jeddah, Alhassa and Dammam, Saudi Arabia. A total of 1369 participants were included. The overall prevalence of LTBI was similar using TST and QFT-GIT (9.3% and 9.1% respectively, p=0.872) but stratified prevalence rates were variable in all sociodemographic groups except marital status. Additionally, the prevalence rates of LTBI using either test alone showed significant differences by several sociodemographic and behavioral characteristics. The overall ARTI was 0.36% using TST and 0.35% using QFT-GIT. We are reporting much lower estimates for the prevalence of LTBI and the ARTI in a population-based sample in Saudi Arabia relative to the data that have been used for more than two decades. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Differences in Mathematics Teachers' Perceived Preparedness to Demonstrate Competence in Secondary School Mathematics Content by Teacher Characteristics

ERIC Educational Resources Information Center

Ng'eno, J. K.; Chesimet, M. C.

2016-01-01

A sample of 300 mathematics teachers drawn from a population of 1500 participated in this study. The participants were selected using systematic random sampling and stratified random sampling (stratified by qualification and gender). The data was collected using self-report questionnaires for mathematics teachers. One tool was used to collect…

Analysis of creative mathematic thinking ability in problem based learning model based on self-regulation learning

NASA Astrophysics Data System (ADS)

Munahefi, D. N.; Waluya, S. B.; Rochmad

2018-03-01

The purpose of this research identified the effectiveness of Problem Based Learning (PBL) models based on Self Regulation Leaning (SRL) on the ability of mathematical creative thinking and analyzed the ability of mathematical creative thinking of high school students in solving mathematical problems. The population of this study was students of grade X SMA N 3 Klaten. The research method used in this research was sequential explanatory. Quantitative stages with simple random sampling technique, where two classes were selected randomly as experimental class was taught with the PBL model based on SRL and control class was taught with expository model. The selection of samples at the qualitative stage was non-probability sampling technique in which each selected 3 students were high, medium, and low academic levels. PBL model with SRL approach effectived to students’ mathematical creative thinking ability. The ability of mathematical creative thinking of low academic level students with PBL model approach of SRL were achieving the aspect of fluency and flexibility. Students of academic level were achieving fluency and flexibility aspects well. But the originality of students at the academic level was not yet well structured. Students of high academic level could reach the aspect of originality.

Protection motivation theory and physical activity: a longitudinal test among a representative population sample of Canadian adults.

PubMed

Plotnikoff, Ronald C; Rhodes, Ryan E; Trinh, Linda

2009-11-01

The purpose of this study was to examine the Protection Motivation Theory (PMT) to predict physical activity (PA) behaviour in a large, population-based sample of adults. One thousand six hundred and two randomly selected individuals completed two telephone interviews over two consecutive six-month periods assessing PMT constructs. PMT explained 35 per cent and 20 per cent of the variance in intention and behaviour respectively. Coping cognitions as moderators of threat explained 1 per cent of the variance in intention and behaviour. Age and gender as moderators of threat did not provide additional variance in the models. We conclude that salient PMT predictors (e.g. self-efficacy) may guide the development of effective PA interventions in the general population.

Seroincidence of non-typhoid Salmonella infections: convenience vs. random community-based sampling.

PubMed

Emborg, H-D; Simonsen, J; Jørgensen, C S; Harritshøj, L H; Krogfelt, K A; Linneberg, A; Mølbak, K

2016-01-01

The incidence of reported infections of non-typhoid Salmonella is affected by biases inherent to passive laboratory surveillance, whereas analysis of blood sera may provide a less biased alternative to estimate the force of Salmonella transmission in humans. We developed a mathematical model that enabled a back-calculation of the annual seroincidence of Salmonella based on measurements of specific antibodies. The aim of the present study was to determine the seroincidence in two convenience samples from 2012 (Danish blood donors, n = 500, and pregnant women, n = 637) and a community-based sample of healthy individuals from 2006 to 2007 (n = 1780). The lowest antibody levels were measured in the samples from the community cohort and the highest in pregnant women. The annual Salmonella seroincidences were 319 infections/1000 pregnant women [90% credibility interval (CrI) 210-441], 182/1000 in blood donors (90% CrI 85-298) and 77/1000 in the community cohort (90% CrI 45-114). Although the differences between study populations decreased when accounting for different age distributions the estimates depend on the study population. It is important to be aware of this issue and define a certain population under surveillance in order to obtain consistent results in an application of serological measures for public health purposes.

Effects of school-based deworming on hemoglobin level, growth development and school performance of primary school children in North Sumatera

NASA Astrophysics Data System (ADS)

Pasaribu, A. P.; Angellee, J.; Pasaribu, S.

2018-03-01

Worm infestation is mainly caused by soil-transmitted helminths (STH) infecting one-third of the world’s population, where the most affected are primary school children. This chronic, long-lasting infection can affect the growth aspects in children. A school-based deworming is one of the treatments recommended by WHO to counterattack worm infection in primary school children. To evaluate the effect of school-based deworming on the hemoglobin level, growth and school performance of primary school children, an open randomized clinical trial was conducted on 165 targeted populations in SukaKaro village, North Sumatra; 156 of which were then chosen based on inclusion and exclusion criteria. The samples’ feces- sampling, hemoglobin level, and growth chart data were recorded on the first day of study before any treatment was given. They were then divided into two groups; the first group of 80 samples did not receive any treatment, while the second group of 76 samples received 400mg of albendazole as part of a school-based deworming program. The samples were being followed up after sixth months of study. In conclusion, albendazole is able to improve the hemoglobin level, growth development, and school performance of the samples, although there were no significant differences between the two groups.

The Reliability of Difference Scores in Populations and Samples

ERIC Educational Resources Information Center

Zimmerman, Donald W.

2009-01-01

This study was an investigation of the relation between the reliability of difference scores, considered as a parameter characterizing a population of examinees, and the reliability estimates obtained from random samples from the population. The parameters in familiar equations for the reliability of difference scores were redefined in such a way…

Challenges to Recruiting Population Representative Samples of Female Sex Workers in China Using Respondent Driven Sampling1

PubMed Central

Merli, M. Giovanna; Moody, James; Smith, Jeffrey; Li, Jing; Weir, Sharon; Chen, Xiangsheng

2014-01-01

We explore the network coverage of a sample of female sex workers (FSWs) in China recruited through Respondent Drive Sampling (RDS) as part of an effort to evaluate the claim of RDS of population representation with empirical data. We take advantage of unique information on the social networks of FSWs obtained from two overlapping studies --RDS and a venue-based sampling approach (PLACE) -- and use an exponential random graph modeling (ERGM) framework from local networks to construct a likely network from which our observed RDS sample is drawn. We then run recruitment chains over this simulated network to assess the assumption that the RDS chain referral process samples participants in proportion to their degree and the extent to which RDS satisfactorily covers certain parts of the network. We find evidence that, contrary to assumptions, RDS oversamples low degree nodes and geographically central areas of the network. Unlike previous evaluations of RDS which have explored the performance of RDS sampling chains on a non-hidden population, or the performance of simulated chains over previously mapped realistic social networks, our study provides a robust, empirically grounded evaluation of the performance of RDS chains on a real-world hidden population. PMID:24834869

Complementary nonparametric analysis of covariance for logistic regression in a randomized clinical trial setting.

PubMed

Tangen, C M; Koch, G G

1999-03-01

In the randomized clinical trial setting, controlling for covariates is expected to produce variance reduction for the treatment parameter estimate and to adjust for random imbalances of covariates between the treatment groups. However, for the logistic regression model, variance reduction is not obviously obtained. This can lead to concerns about the assumptions of the logistic model. We introduce a complementary nonparametric method for covariate adjustment. It provides results that are usually compatible with expectations for analysis of covariance. The only assumptions required are based on randomization and sampling arguments. The resulting treatment parameter is a (unconditional) population average log-odds ratio that has been adjusted for random imbalance of covariates. Data from a randomized clinical trial are used to compare results from the traditional maximum likelihood logistic method with those from the nonparametric logistic method. We examine treatment parameter estimates, corresponding standard errors, and significance levels in models with and without covariate adjustment. In addition, we discuss differences between unconditional population average treatment parameters and conditional subpopulation average treatment parameters. Additional features of the nonparametric method, including stratified (multicenter) and multivariate (multivisit) analyses, are illustrated. Extensions of this methodology to the proportional odds model are also made.

LOD score exclusion analyses for candidate QTLs using random population samples.

PubMed

Deng, Hong-Wen

2003-11-01

While extensive analyses have been conducted to test for, no formal analyses have been conducted to test against, the importance of candidate genes as putative QTLs using random population samples. Previously, we developed an LOD score exclusion mapping approach for candidate genes for complex diseases. Here, we extend this LOD score approach for exclusion analyses of candidate genes for quantitative traits. Under this approach, specific genetic effects (as reflected by heritability) and inheritance models at candidate QTLs can be analyzed and if an LOD score is < or = -2.0, the locus can be excluded from having a heritability larger than that specified. Simulations show that this approach has high power to exclude a candidate gene from having moderate genetic effects if it is not a QTL and is robust to population admixture. Our exclusion analysis complements association analysis for candidate genes as putative QTLs in random population samples. The approach is applied to test the importance of Vitamin D receptor (VDR) gene as a potential QTL underlying the variation of bone mass, an important determinant of osteoporosis.

A random cluster survey and a convenience sample give comparable estimates of immunity to vaccine preventable diseases in children of school age in Victoria, Australia.

PubMed

Kelly, Heath; Riddell, Michaela A; Gidding, Heather F; Nolan, Terry; Gilbert, Gwendolyn L

2002-08-19

We compared estimates of the age-specific population immunity to measles, mumps, rubella, hepatitis B and varicella zoster viruses in Victorian school children obtained by a national sero-survey, using a convenience sample of residual sera from diagnostic laboratories throughout Australia, with those from a three-stage random cluster survey. When grouped according to school age (primary or secondary school) there was no significant difference in the estimates of immunity to measles, mumps, hepatitis B or varicella. Compared with the convenience sample, the random cluster survey estimated higher immunity to rubella in samples from both primary (98.7% versus 93.6%, P = 0.002) and secondary school students (98.4% versus 93.2%, P = 0.03). Despite some limitations, this study suggests that the collection of a convenience sample of sera from diagnostic laboratories is an appropriate sampling strategy to provide population immunity data that will inform Australia's current and future immunisation policies. Copyright 2002 Elsevier Science Ltd.

Efficacy of an internet-based intervention for burnout: a randomized controlled trial in the German working population.

PubMed

Jonas, Benjamin; Leuschner, Fabian; Tossmann, Peter

2017-03-01

Internet-based interventions are a viable treatment option for various mental problems. However, their effects on the burnout syndrome yielded mixed results. In this paper, we examine the efficacy of a structured and therapist-guided internet intervention, based on solution-focused and cognitive-behavioral therapy, for individuals with symptoms of burnout. Two-arm, Internet-based, randomized, wait-list controlled trial (RCT). Participants were recruited through in-house events and online advertising. They were randomly assigned to the intervention or a wait-list. Group comparison was conducted three months after randomization. Outcomes were the burnout level according to the Maslach Burnout Inventory (MBI-GS) and the levels of depression, anxiety and stress according to the DASS-21. Thirty-nine participants were included in the trial; 36 (92.3%) took part at the 3-months-follow-up. Intention-to-treat analyses revealed significant group differences in favor of the intervention group in depression (d = 0.66), cynicism (d = 0.87) and personal accomplishment (d = 0.75). The intervention helped ameliorate symptoms of work-related stress and burnout. Although limited by a small sample size, the study suggests that the program provides effective support for affected individuals. However, further studies with bigger sample sizes should be conducted to examine the effects of such programs more precisely.

Trends in glaucoma surgery incidence and reimbursement for physician services in the Medicare population from 1995 to 1998.

PubMed

Paikal, David; Yu, Fei; Coleman, Anne L

2002-07-01

To better understand the relationship between glaucoma management and economic incentives, we examined the volume and the reimbursement of argon laser trabeculoplasty (ALT) and trabeculectomy in a 5% random sample of the Medicare population from 1995 to 1998. Retrospective cohort study. Subjects in a 5% random sample of the Medicare population who had ALT and trabeculectomy from 1995 to 1998. Using the Health Care Financing Administration (HCFA) Physician/Supplier Part-B files for a 5% random sample of the Medicare population, we identified all subjects who had ALT and trabeculectomy from 1995 to 1998. Descriptive summaries (the number of surgeries and the mean and the standard deviation of reimbursement per surgery) were calculated for each year. Analysis of variance was used to test for differences in reimbursement per surgery across years. Chi-square tests were used to assess any associations between the changing numbers of ALTs and trabeculectomies over the study period and both age and race. We assessed the number of ALTs and trabeculectomies and the allowed charges for each surgery in the 5% random sample of the Medicare population from 1995 to 1998. The volume of both ALTs and trabeculectomies declined during the study period. Reimbursement per surgery for both ALT and trabeculectomy varied significantly across years (P < 0.001). Significant associations were found between the changing number of ALTs and both age and race. Changing numbers of ALT and trabeculectomy seem unrelated to reimbursement rates. Rather, these changes are more likely driven by new developments in the clinical management of glaucoma, among other factors.

The Association of Health and Functional Status with Private and Public Religious Practice among Rural, Ethnically Diverse, Older Adults with Diabetes

ERIC Educational Resources Information Center

Arcury, Thomas A.; Stafford, Jeanette M.; Bell, Ronny A.; Golden, Shannon L.; Snively, Beverly M.; Quandt, Sara A.

2007-01-01

Purpose: This analysis describes the association of health and functional status with private and public religious practice among ethnically diverse (African American, Native American, white) rural older adults with diabetes. Methods: Data were collected using a population-based, cross-sectional, stratified, random sample survey of 701…

Insulation workers in Belfast. 1. Comparison of a random sample with a control population1

PubMed Central

Wallace, William F. M.; Langlands, Jean H. M.

1971-01-01

Wallace, W. F. M., and Langlands, J. H. M. (1971).Brit. J. industr. Med.,28, 211-216. Insulation workers in Belfast. 1. Comparison of a random sample with a control population. A sample of 50 men was chosen at random from the population of asbestos insulators in Belfast and matched with a control series of men of similar occupational group with respect to age, height, and smoking habit. Significantly more of the insulators complained of cough and sputum and had basal rales on examination. Clubbing was assessed by means of measurements of the hyponychial angle of both index fingers. These angles were significantly greater in the group of insulators. Twenty-one insulators had ϰ-rays which showed pleural calcification with or without pulmonary fibrosis; one control ϰ-ray showed pulmonary fibrosis. The insulators had no evidence of airways obstruction but static lung volume was reduced and their arterial oxygen tension was lower than that of the controls and their alveolar-arterial oxygen gradient was greater. PMID:5557841

Sampling pig farms at the abattoir in a cross-sectional study - Evaluation of a sampling method.

PubMed

Birkegård, Anna Camilla; Halasa, Tariq; Toft, Nils

2017-09-15

A cross-sectional study design is relatively inexpensive, fast and easy to conduct when compared to other study designs. Careful planning is essential to obtaining a representative sample of the population, and the recommended approach is to use simple random sampling from an exhaustive list of units in the target population. This approach is rarely feasible in practice, and other sampling procedures must often be adopted. For example, when slaughter pigs are the target population, sampling the pigs on the slaughter line may be an alternative to on-site sampling at a list of farms. However, it is difficult to sample a large number of farms from an exact predefined list, due to the logistics and workflow of an abattoir. Therefore, it is necessary to have a systematic sampling procedure and to evaluate the obtained sample with respect to the study objective. We propose a method for 1) planning, 2) conducting, and 3) evaluating the representativeness and reproducibility of a cross-sectional study when simple random sampling is not possible. We used an example of a cross-sectional study with the aim of quantifying the association of antimicrobial resistance and antimicrobial consumption in Danish slaughter pigs. It was not possible to visit farms within the designated timeframe. Therefore, it was decided to use convenience sampling at the abattoir. Our approach was carried out in three steps: 1) planning: using data from meat inspection to plan at which abattoirs and how many farms to sample; 2) conducting: sampling was carried out at five abattoirs; 3) evaluation: representativeness was evaluated by comparing sampled and non-sampled farms, and the reproducibility of the study was assessed through simulated sampling based on meat inspection data from the period where the actual data collection was carried out. In the cross-sectional study samples were taken from 681 Danish pig farms, during five weeks from February to March 2015. The evaluation showed that the sampling procedure was reproducible with results comparable to the collected sample. However, the sampling procedure favoured sampling of large farms. Furthermore, both under-sampled and over-sampled areas were found using scan statistics. In conclusion, sampling conducted at abattoirs can provide a spatially representative sample. Hence it is a possible cost-effective alternative to simple random sampling. However, it is important to assess the properties of the resulting sample so that any potential selection bias can be addressed when reporting the findings. Copyright © 2017 Elsevier B.V. All rights reserved.

Identifying key demographic parameters of a small island–associated population of Indo-Pacific bottlenose dolphins (Reunion, Indian Ocean)

PubMed Central

Estrade, Vanessa; Fayan, Jacques

2017-01-01

Photo-identification surveys of Indo-Pacific bottlenose dolphins were conducted from 2009 to 2014 off Reunion Island (55°E33’/21°S07’), in the Indian Ocean. Robust Design models were applied to produce the most reliable estimate of population abundance and survival rate, while accounting for temporary emigration from the survey area (west coast). The sampling scheme consisted of a five-month (June–October) sampling period in each year of the study. The overall population size at Reunion was estimated to be 72 individuals (SE = 6.17, 95%CI = 61–85), based on a random temporary emigration (γ”) of 0.096 and a proportion of 0.70 (SE = 0.03) distinct individuals. The annual survival rate was 0.93 (±0.018 SE, 95%CI = 0.886–0.958) and was constant over time and between sexes. Models considering gender groups indicated different movement patterns between males and females. Males showed null or quasi-null temporary emigration (γ” = γ’ < 0.01), while females showed a random temporary emigration (γ”) of 0.10, suggesting that a small proportion of females was outside the survey area during each primary sampling period. Sex-specific temporary migration patterns were consistent with movement and residency patterns observed in other areas. The Robust Design approach provided an appropriate sampling scheme for deriving island-associated population parameters, while allowing to restrict survey effort both spatially (i.e. west coast only) and temporally (five months per year). Although abundance and survival were stable over the six years, the small population size of fewer than 100 individuals suggested that this population is highly vulnerable. Priority should be given to reducing any potential impact of human activity on the population and its habitat. PMID:28640918

Ethnicity, social disadvantage and psychotic-like experiences in a healthy population based sample.

PubMed

Morgan, C; Fisher, H; Hutchinson, G; Kirkbride, J; Craig, T K; Morgan, K; Dazzan, P; Boydell, J; Doody, G A; Jones, P B; Murray, R M; Leff, J; Fearon, P

2009-03-01

We sought to investigate the prevalence and social correlates of psychotic-like experiences in a general population sample of Black and White British subjects. Data were collected from randomly selected community control subjects, recruited as part of the AESOP study, a three-centre population based study of first-episode psychosis. The proportion of subjects reporting one or more psychotic-like experience was 19% (n = 72/372). These were more common in Black Caribbean (OR 2.08) and Black African subjects (OR 4.59), compared with White British. In addition, a number of indicators of childhood and adult disadvantage were associated with psychotic-like experiences. When these variables were simultaneously entered into a regression model, Black African ethnicity, concentrated adult disadvantage, and separation from parents retained a significant effect. The higher prevalence of psychotic-like experiences in the Black Caribbean, but not Black African, group was explained by high levels of social disadvantage over the life course.

A Fosmid Cloning Strategy for Detecting the Widest Possible Spectrum of Microbes from the International Space Station Drinking Water System

PubMed Central

Choi, Sangdun; Chang, Mi Sook; Stuecker, Tara; Chung, Christine; Newcombe, David A.; Venkateswaran, Kasthuri

2012-01-01

In this study, fosmid cloning strategies were used to assess the microbial populations in water from the International Space Station (ISS) drinking water system (henceforth referred to as Prebiocide and Tank A water samples). The goals of this study were: to compare the sensitivity of the fosmid cloning strategy with that of traditional culture-based and 16S rRNA-based approaches and to detect the widest possible spectrum of microbial populations during the water purification process. Initially, microbes could not be cultivated, and conventional PCR failed to amplify 16S rDNA fragments from these low biomass samples. Therefore, randomly primed rolling-circle amplification was used to amplify any DNA that might be present in the samples, followed by size selection by using pulsed-field gel electrophoresis. The amplified high-molecular-weight DNA from both samples was cloned into fosmid vectors. Several hundred clones were randomly selected for sequencing, followed by Blastn/Blastx searches. Sequences encoding specific genes from Burkholderia, a species abundant in the soil and groundwater, were found in both samples. Bradyrhizobium and Mesorhizobium, which belong to rhizobia, a large community of nitrogen fixers often found in association with plant roots, were present in the Prebiocide samples. Ralstonia, which is prevalent in soils with a high heavy metal content, was detected in the Tank A samples. The detection of many unidentified sequences suggests the presence of potentially novel microbial fingerprints. The bacterial diversity detected in this pilot study using a fosmid vector approach was higher than that detected by conventional 16S rRNA gene sequencing. PMID:23346038

Is urbanisation scrambling the genetic structure of human populations? A case study

PubMed Central

Ashrafian-Bonab, Maziar; Handley, Lori Lawson; Balloux, François

2007-01-01

Recent population expansion and increased migration linked to urbanisation are assumed to be eroding the genetic structure of human populations. We investigated change in population structure over three generations by analysing both demographic and mitochondrial DNA (mtDNA) data from a random sample of 2351 men from twenty-two Iranian populations. Potential changes in genetic diversity (θ) and genetic distance (FST) over the last three generations were analysed by assigning mtDNA sequences to populations based on the individual's place of birth or that of their mother or grandmother. Despite the fact that several areas included cities of over one million inhabitants, we detected no change in genetic diversity, and only a small decrease in population structure, except in the capital city (Tehran), which was characterised by massive immigration, increased θ and a large decrease in FST over time. Our results suggest that recent erosion of human population structure might not be as important as previously thought, except in some large conurbations, and this clearly has important implications for future sampling strategies. PMID:17106453

Drivers of disparity: differences in socially based risk factors of self-injurious and suicidal behaviors among sexual minority college students.

PubMed

Blosnich, John; Bossarte, Robert

2012-01-01

Lesbian, gay, and bisexual (ie, sexual minority) populations have increased prevalence of both self-injurious and suicidal behaviors, but reasons for these disparities are poorly understood. To test the association between socially based stressors (eg, victimization, discrimination) and self-injurious behavior, suicide ideation, and suicide attempt. A national sample of college-attending 18- to 24-year-olds. Random or census samples from postsecondary educational institutions that administered the National College Health Assessment during the Fall 2008 and Spring 2009 semesters. Sexual minorities reported more socially based stressors than heterosexuals. Bisexuals exhibited greatest prevalence of self-injurious and suicidal behaviors. In adjusted models, intimate partner violence was most consistently associated with self-injurious behaviors. Sexual minorities' elevated risks of self-injurious and suicidal behaviors may stem from higher exposure to socially based stressors. Within-group differences among sexual minorities offer insight to specific risk factors that may contribute to elevated self-injurious and suicidal behaviors in sexual minority populations.

Sample design effects in landscape genetics

USGS Publications Warehouse

Oyler-McCance, Sara J.; Fedy, Bradley C.; Landguth, Erin L.

2012-01-01

An important research gap in landscape genetics is the impact of different field sampling designs on the ability to detect the effects of landscape pattern on gene flow. We evaluated how five different sampling regimes (random, linear, systematic, cluster, and single study site) affected the probability of correctly identifying the generating landscape process of population structure. Sampling regimes were chosen to represent a suite of designs common in field studies. We used genetic data generated from a spatially-explicit, individual-based program and simulated gene flow in a continuous population across a landscape with gradual spatial changes in resistance to movement. Additionally, we evaluated the sampling regimes using realistic and obtainable number of loci (10 and 20), number of alleles per locus (5 and 10), number of individuals sampled (10-300), and generational time after the landscape was introduced (20 and 400). For a simulated continuously distributed species, we found that random, linear, and systematic sampling regimes performed well with high sample sizes (>200), levels of polymorphism (10 alleles per locus), and number of molecular markers (20). The cluster and single study site sampling regimes were not able to correctly identify the generating process under any conditions and thus, are not advisable strategies for scenarios similar to our simulations. Our research emphasizes the importance of sampling data at ecologically appropriate spatial and temporal scales and suggests careful consideration for sampling near landscape components that are likely to most influence the genetic structure of the species. In addition, simulating sampling designs a priori could help guide filed data collection efforts.

Pilot Test of a Novel Method for Assessing Community Response to Low-Amplitude Sonic Booms

NASA Technical Reports Server (NTRS)

Fidell, Sanford; Horonjeff, Richard D.; Harris, Michael

2012-01-01

A pilot test of a novel method for assessing residents annoyance to sonic booms was performed. During a two-week period, residents of the base housing area at Edwards Air Force Base provided data on their reactions to sonic booms using Smartphone-based interviews. Noise measurements were conducted at the same time. The report presents information about data collection methods and about test participants reactions to low-amplitude sonic booms. The latter information should not be viewed as definitive for several reasons. It may not be reliably generalized to the wider U.S. residential population (because it was not derived from a representative random sample) and the sample itself was not large.

Adaptive cluster sampling: An efficient method for assessing inconspicuous species

Treesearch

Andrea M. Silletti; Joan Walker

2003-01-01

Restorationistis typically evaluate the success of a project by estimating the population sizes of species that have been planted or seeded. Because total census is raely feasible, they must rely on sampling methods for population estimates. However, traditional random sampling designs may be inefficient for species that, for one reason or another, are challenging to...

Generalizability of causal inference in observational studies under retrospective convenience sampling.

PubMed

Hu, Zonghui; Qin, Jing

2018-05-20

Many observational studies adopt what we call retrospective convenience sampling (RCS). With the sample size in each arm prespecified, RCS randomly selects subjects from the treatment-inclined subpopulation into the treatment arm and those from the control-inclined into the control arm. Samples in each arm are representative of the respective subpopulation, but the proportion of the 2 subpopulations is usually not preserved in the sample data. We show in this work that, under RCS, existing causal effect estimators actually estimate the treatment effect over the sample population instead of the underlying study population. We investigate how to correct existing methods for consistent estimation of the treatment effect over the underlying population. Although RCS is adopted in medical studies for ethical and cost-effective purposes, it also has a big advantage for statistical inference: When the tendency to receive treatment is low in a study population, treatment effect estimators under RCS, with proper correction, are more efficient than their parallels under random sampling. These properties are investigated both theoretically and through numerical demonstration. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Ant-inspired density estimation via random walks

PubMed Central

Musco, Cameron; Su, Hsin-Hao

2017-01-01

Many ant species use distributed population density estimation in applications ranging from quorum sensing, to task allocation, to appraisal of enemy colony strength. It has been shown that ants estimate local population density by tracking encounter rates: The higher the density, the more often the ants bump into each other. We study distributed density estimation from a theoretical perspective. We prove that a group of anonymous agents randomly walking on a grid are able to estimate their density within a small multiplicative error in few steps by measuring their rates of encounter with other agents. Despite dependencies inherent in the fact that nearby agents may collide repeatedly (and, worse, cannot recognize when this happens), our bound nearly matches what would be required to estimate density by independently sampling grid locations. From a biological perspective, our work helps shed light on how ants and other social insects can obtain relatively accurate density estimates via encounter rates. From a technical perspective, our analysis provides tools for understanding complex dependencies in the collision probabilities of multiple random walks. We bound the strength of these dependencies using local mixing properties of the underlying graph. Our results extend beyond the grid to more general graphs, and we discuss applications to size estimation for social networks, density estimation for robot swarms, and random walk-based sampling for sensor networks. PMID:28928146

Improvement of Predictive Ability by Uniform Coverage of the Target Genetic Space

PubMed Central

Bustos-Korts, Daniela; Malosetti, Marcos; Chapman, Scott; Biddulph, Ben; van Eeuwijk, Fred

2016-01-01

Genome-enabled prediction provides breeders with the means to increase the number of genotypes that can be evaluated for selection. One of the major challenges in genome-enabled prediction is how to construct a training set of genotypes from a calibration set that represents the target population of genotypes, where the calibration set is composed of a training and validation set. A random sampling protocol of genotypes from the calibration set will lead to low quality coverage of the total genetic space by the training set when the calibration set contains population structure. As a consequence, predictive ability will be affected negatively, because some parts of the genotypic diversity in the target population will be under-represented in the training set, whereas other parts will be over-represented. Therefore, we propose a training set construction method that uniformly samples the genetic space spanned by the target population of genotypes, thereby increasing predictive ability. To evaluate our method, we constructed training sets alongside with the identification of corresponding genomic prediction models for four genotype panels that differed in the amount of population structure they contained (maize Flint, maize Dent, wheat, and rice). Training sets were constructed using uniform sampling, stratified-uniform sampling, stratified sampling and random sampling. We compared these methods with a method that maximizes the generalized coefficient of determination (CD). Several training set sizes were considered. We investigated four genomic prediction models: multi-locus QTL models, GBLUP models, combinations of QTL and GBLUPs, and Reproducing Kernel Hilbert Space (RKHS) models. For the maize and wheat panels, construction of the training set under uniform sampling led to a larger predictive ability than under stratified and random sampling. The results of our methods were similar to those of the CD method. For the rice panel, all training set construction methods led to similar predictive ability, a reflection of the very strong population structure in this panel. PMID:27672112

Assessing relative abundance and reproductive success of shrubsteppe raptors

USGS Publications Warehouse

Lehman, Robert N.; Carpenter, L.B.; Steenhof, Karen; Kochert, Michael N.

1998-01-01

From 1991-1994, we quantified relative abundance and reproductive success of the Ferruginous Hawk (Buteo regalis), Northern Harrier (Circus cyaneus), Burrowing Owl (Speotytoc unicularia), and Short-eared Owl (Asio flammeus) on the shrubsteppe plateaus (benchlands) in and near the Snake River Birds of Prey National Conservation Area in southwestern Idaho. To assess relative abundance, we searched randomly selected plots using four sampling methods: point counts, line transects, and quadrats of two sizes. On a persampling-effort basis, transects were slightly more effective than point counts and quadrats for locating raptor nests (3.4 pairs detected/100 h of effort vs. 2.2-3.1 pairs). Random sampling using quadrats failed to detect a Short-eared Owl population increase from 1993 to 1994. To evaluate nesting success, we tried to determine reproductive outcome for all nesting attempts located during random, historical, and incidental nest searches. We compared nesting success estimates based on all nesting attempts, on attempts found during incubation, and the Mayfield model. Most pairs used to evaluate success were pairs found incidentally. Visits to historical nesting areas yielded the highest number of pairs per sampling effort (14.6/100 h), but reoccupancy rates for most species decreased through time. Estimates based on all attempts had the highest sample sizes but probably overestimated success for all species except the Ferruginous Hawk. Estimates of success based on nesting attempts found during incubation had the lowest sample sizes. All three methods yielded biased nesting snccess estimates for the Northern Harrier and Short-eared Owl. The estimate based on pairs found during incubation probably provided the least biased estimate for the Burrowing Owl. Assessments of nesting success were hindered by difficulties in confirming egg laying and nesting success for all species except the Ferruginous hawk.

Simultaneous genomic identification and profiling of a single cell using semiconductor-based next generation sequencing.

PubMed

Watanabe, Manabu; Kusano, Junko; Ohtaki, Shinsaku; Ishikura, Takashi; Katayama, Jin; Koguchi, Akira; Paumen, Michael; Hayashi, Yoshiharu

2014-09-01

Combining single-cell methods and next-generation sequencing should provide a powerful means to understand single-cell biology and obviate the effects of sample heterogeneity. Here we report a single-cell identification method and seamless cancer gene profiling using semiconductor-based massively parallel sequencing. A549 cells (adenocarcinomic human alveolar basal epithelial cell line) were used as a model. Single-cell capture was performed using laser capture microdissection (LCM) with an Arcturus® XT system, and a captured single cell and a bulk population of A549 cells (≈ 10(6) cells) were subjected to whole genome amplification (WGA). For cell identification, a multiplex PCR method (AmpliSeq™ SNP HID panel) was used to enrich 136 highly discriminatory SNPs with a genotype concordance probability of 10(31-35). For cancer gene profiling, we used mutation profiling that was performed in parallel using a hotspot panel for 50 cancer-related genes. Sequencing was performed using a semiconductor-based bench top sequencer. The distribution of sequence reads for both HID and Cancer panel amplicons was consistent across these samples. For the bulk population of cells, the percentages of sequence covered at coverage of more than 100 × were 99.04% for the HID panel and 98.83% for the Cancer panel, while for the single cell percentages of sequence covered at coverage of more than 100 × were 55.93% for the HID panel and 65.96% for the Cancer panel. Partial amplification failure or randomly distributed non-amplified regions across samples from single cells during the WGA procedures or random allele drop out probably caused these differences. However, comparative analyses showed that this method successfully discriminated a single A549 cancer cell from a bulk population of A549 cells. Thus, our approach provides a powerful means to overcome tumor sample heterogeneity when searching for somatic mutations.

Development of Activity and Participation Norms among General Adult Populations in Taiwan.

PubMed

Yen, Chia-Feng; Chiu, Tzu-Ying; Liou, Tsan-Hon; Chi, Wen-Chou; Liao, Hua-Fang; Liang, Chung-Chao; Escorpizo, Reuben

2017-06-06

Based on the International Classification of Functioning, Disability, and Health (ICF) and the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0), The Functioning Disability Evaluation Scale-Adult version (FUNDES-Adult) began development in 2011. The FUNDES-Adult was designed to assess the difficulty level of an individual's activities and participation in daily life. There is a lack of research regarding the profile of activity and participation for the general adult population. The purposes of this study were to establish activity and participation norms for the general adult population in Taiwan and to describe, discuss, and compare the activity and participation profile with other population. A population-based survey was administered in 2013 using a computer-assisted telephone interviewing system (CATI system). Using probability proportional to size (PPS) sampling and systematic sampling with random digit dialing (RDD), 1500 adults from Taiwan's general population were selected to participate in the survey. The FUNDES-Adult with six domains and two dimensions (performance and capability) was used to obtain data on activities and participation levels. A higher domain score indicated higher participation restriction. Approximately 50% of the respondents were male, and the average age of the respondents was 45.23 years. There were no significant differences in the demographic features between the sample and the population. Among the six domains, the self-care domain score was the lowest (least restriction) and the participation domain score was the highest (most restriction). Approximately 90% of the sample scored were less than 15, and only 0.1% scored more than 80. This is the first cross-national population-based survey to assess norms of activity and participation relevant to the general population of Taiwan. As such, the results of this survey can be used as a reference for comparing the activity and participation (AP) functioning of other countries and subgroups.

Smoking reduces fecundity: a European multicenter study on infertility and subfecundity. The European Study Group on Infertility and Subfecundity.

PubMed

Bolumar, F; Olsen, J; Boldsen, J

1996-03-15

Several studies published within the past 10 years indicate that smoking reduces fecundity, but not all studies have found this effect, and smoking cessation is not used routinely in infertility treatment in Europe. The present study was designed to examine male and female smoking at the start of a couple's waiting time to a planned pregnancy. Two types of samples were used: population-based samples of women aged 25-44 years who were randomly selected in different countries from census registers and electoral rolls, in which the unit of analysis was the couple; and pregnancy-based samples of pregnant women (at least 20 weeks' pregnant) who were consecutively recruited during prenatal care visits, in which the unit of analysis was a pregnancy. More than 4,000 couples were included in each sample, and 10 different regions in Europe took part in data collection. The data were collected between August 1991 and February 1993 by personal interview in all population-based samples and in all but three regions of the pregnancy sample, where self-administered questionnaires were used. The results based on the population sample showed a remarkably coherent association between female smoking and subfecundity in each individual country and in all countries together, both with the first pregnancy (odds ratio (OR) = 1.7, 95% confidence interval (CI) 1.3-2.1, at the upper level of exposure) and during the most recent waiting time to pregnancy (OR = 1.6, 95% CI 1.3-2.1). Results based on the pregnancy sample were similar (OR = 1.7, 95% CI 1.3-2.3). No significant association was found with male smoking (in the population sample, OR = 0.9, 95% CI 0.7-1.1 (first pregnancy) and OR = 1.0, 95% CI 0.9-1.3 (most recent waiting time); in the pregnancy sample, OR = 0.9, 95% CI 0.7-1.1). The fecundity distribution among smokers appeared to be shifted toward longer waiting times without a change in the shape of the distribution. Women who have difficulty conceiving should try to stop smoking or to reduce their smoking to less than 10 cigarettes per day.

Population entropies estimates of proteins

NASA Astrophysics Data System (ADS)

Low, Wai Yee

2017-05-01

The Shannon entropy equation provides a way to estimate variability of amino acids sequences in a multiple sequence alignment of proteins. Knowledge of protein variability is useful in many areas such as vaccine design, identification of antibody binding sites, and exploration of protein 3D structural properties. In cases where the population entropies of a protein are of interest but only a small sample size can be obtained, a method based on linear regression and random subsampling can be used to estimate the population entropy. This method is useful for comparisons of entropies where the actual sequence counts differ and thus, correction for alignment size bias is needed. In the current work, an R based package named EntropyCorrect that enables estimation of population entropy is presented and an empirical study on how well this new algorithm performs on simulated dataset of various combinations of population and sample sizes is discussed. The package is available at https://github.com/lloydlow/EntropyCorrect. This article, which was originally published online on 12 May 2017, contained an error in Eq. (1), where the summation sign was missing. The corrected equation appears in the Corrigendum attached to the pdf.

Enhancing local health department disaster response capacity with rapid community needs assessments: validation of a computerized program for binary attribute cluster sampling.

PubMed

Groenewold, Matthew R

2006-01-01

Local health departments are among the first agencies to respond to disasters or other mass emergencies. However, they often lack the ability to handle large-scale events. Plans including locally developed and deployed tools may enhance local response. Simplified cluster sampling methods can be useful in assessing community needs after a sudden-onset, short duration event. Using an adaptation of the methodology used by the World Health Organization Expanded Programme on Immunization (EPI), a Microsoft Access-based application for two-stage cluster sampling of residential addresses in Louisville/Jefferson County Metro, Kentucky was developed. The sampling frame was derived from geographically referenced data on residential addresses and political districts available through the Louisville/Jefferson County Information Consortium (LOJIC). The program randomly selected 30 clusters, defined as election precincts, from within the area of interest, and then, randomly selected 10 residential addresses from each cluster. The program, called the Rapid Assessment Tools Package (RATP), was tested in terms of accuracy and precision using data on a dichotomous characteristic of residential addresses available from the local tax assessor database. A series of 30 samples were produced and analyzed with respect to their precision and accuracy in estimating the prevalence of the study attribute. Point estimates with 95% confidence intervals were calculated by determining the proportion of the study attribute values in each of the samples and compared with the population proportion. To estimate the design effect, corresponding simple random samples of 300 addresses were taken after each of the 30 cluster samples. The sample proportion fell within +/-10 absolute percentage points of the true proportion in 80% of the samples. In 93.3% of the samples, the point estimate fell within +/-12.5%, and 96.7% fell within +/-15%. All of the point estimates fell within +/-20% of the true proportion. Estimates of the design effect ranged from 0.926 to 1.436 (mean = 1.157, median = 1.170) for the 30 samples. Although prospective evaluation of its performance in field trials or a real emergency is required to confirm its utility, this study suggests that the RATP, a locally designed and deployed tool, may provide population-based estimates of community needs or the extent of event-related consequences that are precise enough to serve as the basis for the initial post-event decisions regarding relief efforts.

Out-of-pocket costs for cancer survivors between 5 and 10 years from diagnosis: an Italian population-based study.

PubMed

Baili, Paolo; Di Salvo, Francesca; de Lorenzo, Francesco; Maietta, Francesco; Pinto, Carmine; Rizzotto, Vera; Vicentini, Massimo; Rossi, Paolo Giorgi; Tumino, Rosario; Rollo, Patrizia Concetta; Tagliabue, Giovanna; Contiero, Paolo; Candela, Pina; Scuderi, Tiziana; Iannelli, Elisabetta; Cascinu, Stefano; Aurora, Fulvio; Agresti, Roberto; Turco, Alberto; Sant, Milena; Meneghini, Elisabetta; Micheli, Andrea

2016-05-01

To illustrate the out-of-pocket (OOP) costs incurred by a population-based group of patients from 5 to 10 years since their cancer diagnosis in a country with a nationwide public health system. Interviews on OOP costs to a sample of 5-10 year prevalent cases randomly extracted from four population-based cancer registries (CRs), two in the north and two in the south of Italy. The patients' general practitioners (GPs) gave assurance about the patient's physical and psychological condition for the interview. A zero-inflated negative binomial model was used to analyze OOP cost determinants. Two hundred six cancer patients were interviewed (48 % of the original sample). On average, a patient in the north spent €69 monthly, against €244 in the south. The main differences are for transport, room, and board (TRB) to reach the hospital and/or the cancer specialist (north €0; south €119). Everywhere, OOP costs without TRB costs were higher for patients with a low quality of life. Despite the limited participation, our study sample's characteristics are similar to those of the Italian cancer prevalence population, allowing us to generalize the results. The higher OOP costs in the south may be due to the scarcity of oncologic structures, obliging patients to seek assistance far from their residence. Implications for cancer survivors Cancer survivors need descriptive studies to show realistic data about their status. Future Italian and European descriptive studies on cancer survivorship should be based on population CRs and involve GPs in order to approach the patient at best.

An in silico approach helped to identify the best experimental design, population, and outcome for future randomized clinical trials.

PubMed

Bajard, Agathe; Chabaud, Sylvie; Cornu, Catherine; Castellan, Anne-Charlotte; Malik, Salma; Kurbatova, Polina; Volpert, Vitaly; Eymard, Nathalie; Kassai, Behrouz; Nony, Patrice

2016-01-01

The main objective of our work was to compare different randomized clinical trial (RCT) experimental designs in terms of power, accuracy of the estimation of treatment effect, and number of patients receiving active treatment using in silico simulations. A virtual population of patients was simulated and randomized in potential clinical trials. Treatment effect was modeled using a dose-effect relation for quantitative or qualitative outcomes. Different experimental designs were considered, and performances between designs were compared. One thousand clinical trials were simulated for each design based on an example of modeled disease. According to simulation results, the number of patients needed to reach 80% power was 50 for crossover, 60 for parallel or randomized withdrawal, 65 for drop the loser (DL), and 70 for early escape or play the winner (PW). For a given sample size, each design had its own advantage: low duration (parallel, early escape), high statistical power and precision (crossover), and higher number of patients receiving the active treatment (PW and DL). Our approach can help to identify the best experimental design, population, and outcome for future RCTs. This may be particularly useful for drug development in rare diseases, theragnostic approaches, or personalized medicine. Copyright © 2016 Elsevier Inc. All rights reserved.

One-step estimation of networked population size: Respondent-driven capture-recapture with anonymity.

PubMed

Khan, Bilal; Lee, Hsuan-Wei; Fellows, Ian; Dombrowski, Kirk

2018-01-01

Size estimation is particularly important for populations whose members experience disproportionate health issues or pose elevated health risks to the ambient social structures in which they are embedded. Efforts to derive size estimates are often frustrated when the population is hidden or hard-to-reach in ways that preclude conventional survey strategies, as is the case when social stigma is associated with group membership or when group members are involved in illegal activities. This paper extends prior research on the problem of network population size estimation, building on established survey/sampling methodologies commonly used with hard-to-reach groups. Three novel one-step, network-based population size estimators are presented, for use in the context of uniform random sampling, respondent-driven sampling, and when networks exhibit significant clustering effects. We give provably sufficient conditions for the consistency of these estimators in large configuration networks. Simulation experiments across a wide range of synthetic network topologies validate the performance of the estimators, which also perform well on a real-world location-based social networking data set with significant clustering. Finally, the proposed schemes are extended to allow them to be used in settings where participant anonymity is required. Systematic experiments show favorable tradeoffs between anonymity guarantees and estimator performance. Taken together, we demonstrate that reasonable population size estimates are derived from anonymous respondent driven samples of 250-750 individuals, within ambient populations of 5,000-40,000. The method thus represents a novel and cost-effective means for health planners and those agencies concerned with health and disease surveillance to estimate the size of hidden populations. We discuss limitations and future work in the concluding section.

Infant and toddler disease score was useful for risk of hospitalization based on data from administrative claims.

PubMed

Mikaeloff, Yann; Moride, Yola; Khoshnood, Babak; Weill, Alain; Bréart, Gérard

2007-07-01

To develop the infant and toddler disease score (IDS), a population-based predictive tool of morbidity status in infants and toddlers, based on data from administrative claims. A prospective cohort study was conducted, including 35,580 children less than 2 years of age in June 2003 from the French "ERASME" database (mean follow-up 13 months). The outcome variable was incident hospitalization during the follow-up year, that is, before the second birthday for infants and before the third for toddlers. Risk factors before inclusion (age, health care use, medications) were assessed in a 50% random sample (construction sample) by a logistic regression model. Beta coefficients were summed up to obtain the IDS. The IDS was then validated for the remaining 50% of the study population (validation sample). The major variables significantly associated with the outcome were long-term disability, younger age, and >or=1 hospitalization before inclusion. The risks of hospitalization estimated by the IDS were concordant in the construction and validation samples. The IDS is a useful index for the risk of hospitalization of infants and toddlers in relation to their morbidity status and may be used for adjustment in pharmacoepidemiologic studies using administrative claims databases.

Determining individual variation in growth and its implication for life-history and population processes using the empirical Bayes method.

PubMed

Vincenzi, Simone; Mangel, Marc; Crivelli, Alain J; Munch, Stephan; Skaug, Hans J

2014-09-01

The differences in demographic and life-history processes between organisms living in the same population have important consequences for ecological and evolutionary dynamics. Modern statistical and computational methods allow the investigation of individual and shared (among homogeneous groups) determinants of the observed variation in growth. We use an Empirical Bayes approach to estimate individual and shared variation in somatic growth using a von Bertalanffy growth model with random effects. To illustrate the power and generality of the method, we consider two populations of marble trout Salmo marmoratus living in Slovenian streams, where individually tagged fish have been sampled for more than 15 years. We use year-of-birth cohort, population density during the first year of life, and individual random effects as potential predictors of the von Bertalanffy growth function's parameters k (rate of growth) and L∞ (asymptotic size). Our results showed that size ranks were largely maintained throughout marble trout lifetime in both populations. According to the Akaike Information Criterion (AIC), the best models showed different growth patterns for year-of-birth cohorts as well as the existence of substantial individual variation in growth trajectories after accounting for the cohort effect. For both populations, models including density during the first year of life showed that growth tended to decrease with increasing population density early in life. Model validation showed that predictions of individual growth trajectories using the random-effects model were more accurate than predictions based on mean size-at-age of fish.

Rationale and Methodology for a Community-Based Study of Diabetic Retinopathy in an Indonesian Population with Type 2 Diabetes Mellitus: The Jogjakarta Eye Diabetic Study in the Community.

PubMed

Sasongko, Muhammad B; Agni, Angela N; Wardhana, Firman S; Kotha, Satya P; Gupta, Prateek; Widayanti, Tri W; Supanji; Widyaputri, Felicia; Widyaningrum, Rifa; Wong, Tien Y; Kawasaki, Ryo; Wang, Jie Jin; Pawiroranu, Suhardjo

2017-02-01

There are no available data about diabetic retinopathy (DR) in the Indonesian population. This report summarizes the rationale and study design of the Jogjakarta Eye Diabetic Study in the Community (JOGED.COM), a community-based study to estimate the prevalence and risk factors of DR in persons with type 2 diabetes in Jogjakarta, Indonesia. The JOGED.COM aimed to examine a cross-sectional sample of 1200 persons with type 2 diabetes aged 30 years and older residing in the study area. We identified 121 community health centers (CHCs) in Jogjakarta and listed 35 CHCs with non-communicable diseases facilities. Multi-stage, clustered random sampling was used to select 22 CHCs randomly. We included CHCs with coverage population >30,000, and excluded those classified as 100% rural. Lists of persons with diabetes confirmed by their family physician were provided from each CHC. Examinations procedures included detailed interviews, general and eye examinations, anthropometry and body composition scan, and dilated fundus photography. We collaborated with local health authorities, family physicians, and local health practitioners in the recruitment phase. A total of 1435 invitations were distributed, and 1184 people (82.5%) with type 2 diabetes participated in this study, of whom 1138 (79.3%) had completed data with gradable retinal images. JOGED.COM is the first epidemiologic study of DR in an Indonesian population. This study will provide key information about the prevalence and risk factors of DR in the community. These data are very important for future health promotion programs to reduce the burden of DR in the population.

How Generalizable Is Your Experiment? An Index for Comparing Experimental Samples and Populations

ERIC Educational Resources Information Center

Tipton, Elizabeth

2014-01-01

Although a large-scale experiment can provide an estimate of the average causal impact for a program, the sample of sites included in the experiment is often not drawn randomly from the inference population of interest. In this article, we provide a generalizability index that can be used to assess the degree of similarity between the sample of…

Representative Sampling: Follow-up of Spring 1972 and Spring 1973 Students. TEX-SIS FOLLOW-UP SC3.

ERIC Educational Resources Information Center

Wilkinson, Larry; And Others

This report presents the findings of a research study, conducted by the College of the Mainland (COM) as a subcontractor for Project FOLLOW-UP, designed to test the accuracy of random sampling and to measure non-response bias in mail surveys. In 1975, a computer-generated random sample of 500 students was drawn from a population of 1,256 students…

A Population of Assessment Tasks

ERIC Educational Resources Information Center

Daro, Phil; Burkhardt, Hugh

2012-01-01

We propose the development of a "population" of high-quality assessment tasks that cover the performance goals set out in the "Common Core State Standards for Mathematics." The population will be published. Tests are drawn from this population as a structured random sample guided by a "balancing algorithm."

Endothelial Nitric Oxide Synthase (G894T) Gene Polymorphism in a Random Sample of the Egyptian Population: Comparison with Myocardial Infarction Patients

PubMed Central

Abdel Rahman, Mohamed F.; Hashad, Ingy M.; Abdel-Maksoud, Sahar M.; Farag, Nabil M.; Abou-Aisha, Khaled

2012-01-01

Aim: The aim of this study was to detect endothelial nitric oxide synthase (eNOS) Glu298Asp gene variants in a random sample of the Egyptian population, compare it with those from other populations, and attempt to correlate these variants with serum levels of nitric oxide (NO). The association of eNOS genotypes or serum NO levels with the incidence of acute myocardial infarction (AMI) was also examined. Methods: One hundred one unrelated healthy subjects and 104 unrelated AMI patients were recruited randomly from the 57357 Hospital and intensive care units of El Demerdash Hospital and National Heart Institute, Cairo, Egypt. eNOS genotypes were determined by polymerase chain reaction–restriction fragment length polymorphism. Serum NO was determined spectrophotometrically. Results: The genotype distribution of eNOS Glu298Asp polymorphism determined for our sample was 58.42% GG (wild type), 33.66% GT, and 7.92% TT genotypes while allele frequencies were 75.25% and 24.75% for G and T alleles, respectively. No significant association between serum NO and specific eNOS genotype could be detected. No significant correlation between eNOS genotype distribution or allele frequencies and the incidence of AMI was observed. Conclusion: The present study demonstrated the predominance of the homozygous genotype GG over the heterozygous GT and homozygous TT in random samples of Egyptian population. It also showed the lack of association between eNOS genotypes and mean serum levels of NO, as well as the incidence of AMI. PMID:22731641

Physiogenomic analysis of the Puerto Rican population.

PubMed

Ruaño, Gualberto; Duconge, Jorge; Windemuth, Andreas; Cadilla, Carmen L; Kocherla, Mohan; Villagra, David; Renta, Jessica; Holford, Theodore; Santiago-Borrero, Pedro J

2009-04-01

Admixture in the population of the island of Puerto Rico is of general interest with regards to pharmacogenetics to develop comprehensive strategies for personalized healthcare in Latin Americans. This research was aimed at determining the frequencies of SNPs in key physiological, pharmacological and biochemical genes to infer population structure and ancestry in the Puerto Rican population. A noninterventional, cross-sectional, retrospective study design was implemented following a controlled, stratified-by-region, random sampling protocol. The sample was based on birthrates in each region of the island of Puerto Rico, according to the 2004 National Birth Registry. Genomic DNA samples from 100 newborns were obtained from the Puerto Rico Newborn Screening Program in dried-blood spot cards. Genotyping using a physiogenomic array was performed for 332 SNPs from 196 cardiometabolic and neuroendocrine genes. Population structure was examined using a Bayesian clustering approach as well as by allelic dissimilarity as a measure of allele sharing. The Puerto Rican sample was found to be broadly heterogeneous. We observed three main clusters in the population, which we hypothesize to reflect the historical admixture in the Puerto Rican population from Amerindian, African and European ancestors. We present evidence for this interpretation by comparing allele frequencies for the three clusters with those for the same SNPs available from the International HapMap project for Asian, African and European populations. Our results demonstrate that population analysis can be performed with a physiogenomic array of cardiometabolic and neuroendocrine genes to facilitate the translation of genome diversity into personalized medicine.

Comparing Study Populations of Men Who Have Sex with Men: Evaluating Consistency Within Repeat Studies and Across Studies in the Seattle Area Using Different Recruitment Methodologies

PubMed Central

Burt, Richard D.; Oster, Alexandra M.; Golden, Mathew R.; Thiede, Hanne

2013-01-01

There is no gold standard for recruiting unbiased samples of men who have sex with men (MSM). To assess differing recruitment methods, we compared Seattle-area MSM samples from: venue-day-time sampling-based National HIV Behavioral Surveillance (NHBS) surveys in 2008 and 2011, random-digit-dialed (RDD) surveys in 2003 and 2006, and STD clinic patient data 2001–2011. We compared sociodemographics, sexual and drug-associated behavior, and HIV status and testing. There was generally good consistency between the two NHBS surveys and within STD clinic data across time. NHBS participants reported higher levels of drug-associated and lower levels of sexual risk than STD clinic patients. RDD participants differed from the other study populations in sociodemographics and some risk behaviors. While neither NHBS nor the STD clinic study populations may be representative of all MSM, both appear to provide consistent samples of MSM subpopulations across time that can provide useful information to guide HIV prevention. PMID:23900958

Molecular diagnosis of strongyloidiasis in a population of an endemic area through nested-PCR.

PubMed

Sharifdini, Meysam; Keyhani, Amir; Eshraghian, Mohammad Reza; Beigom Kia, Eshrat

2018-01-01

This study is aimed to diagnose and analyze strongyloidiasis in a population of an endemic area of Iran using nested-PCR, coupled with parasitological methods. Screening of strongyloidiasis infected people using reliable diagnostic techniques are essential to decrease the mortality and morbidity associated with this infection. Molecular methods have been proved to be highly sensitive and specific for detection of Strongyloides stercoralis in stool samples. A total of 155 fresh single stool samples were randomly collected from residents of north and northwest of Khouzestan Province, Iran. All samples were examined by parasitological methods including formalin-ether concentration and nutrient agar plate culture, and molecular method of nested-PCR. Infections with S. stercoralis were analyzed according to demographic criteria. Based on the results of nested-PCR method 15 cases (9.7%) were strongyloidiasis positive. Nested-PCR was more sensitive than parasitological techniques on single stool sampling. Elderly was the most important population index for higher infectivity with S. stercoralis . In endemic areas of S. stercoralis , old age should be considered as one of the most important risk factors of infection, especially among the immunosuppressed individuals.

Control of diabetes and fibrinogen levels as well as improvement in health care might delay low cognitive performance in societies aging progressively.

PubMed

Lopes, Daniele Almeida; Moraes, Suzana Alves de; Freitas, Isabel Cristina Martins de

2015-01-01

To know the prevalence and factors associated to low cognitive performance in a representative sample of the adult population in a society aging progressively. Cross-sectional population-based study carried out in a three-stage sampling: 81 census tracts (primary sampling unity) were randomly selected, followed by 1,672 households and 2,471 participants (weighted sample) corresponding to the second and third stages, respectively. The outcome prevalence was calculated according sociodemographic, behavioral and health related variables. Crude and adjusted prevalence ratios were estimated using Poisson regression. The prevalence of low cognitive performance was high, mainly among females, and indicated linear trends into categories of age, schooling, income, plasma fibrinogen and self-reported health status. In multivariate models, gender, diabetes, fibrinogen and self-reported health status presented positive associations, while schooling, employment and sitting time presented negative associations with the outcome. Interventions related to diabetes and fibrinogen levels control as well as improvement in health care might delay low cognitive performance in societies aging progressively as such the study population.

Network Sampling with Memory: A proposal for more efficient sampling from social networks.

PubMed

Mouw, Ted; Verdery, Ashton M

2012-08-01

Techniques for sampling from networks have grown into an important area of research across several fields. For sociologists, the possibility of sampling from a network is appealing for two reasons: (1) A network sample can yield substantively interesting data about network structures and social interactions, and (2) it is useful in situations where study populations are difficult or impossible to survey with traditional sampling approaches because of the lack of a sampling frame. Despite its appeal, methodological concerns about the precision and accuracy of network-based sampling methods remain. In particular, recent research has shown that sampling from a network using a random walk based approach such as Respondent Driven Sampling (RDS) can result in high design effects (DE)-the ratio of the sampling variance to the sampling variance of simple random sampling (SRS). A high design effect means that more cases must be collected to achieve the same level of precision as SRS. In this paper we propose an alternative strategy, Network Sampling with Memory (NSM), which collects network data from respondents in order to reduce design effects and, correspondingly, the number of interviews needed to achieve a given level of statistical power. NSM combines a "List" mode, where all individuals on the revealed network list are sampled with the same cumulative probability, with a "Search" mode, which gives priority to bridge nodes connecting the current sample to unexplored parts of the network. We test the relative efficiency of NSM compared to RDS and SRS on 162 school and university networks from Add Health and Facebook that range in size from 110 to 16,278 nodes. The results show that the average design effect for NSM on these 162 networks is 1.16, which is very close to the efficiency of a simple random sample (DE=1), and 98.5% lower than the average DE we observed for RDS.

Network Sampling with Memory: A proposal for more efficient sampling from social networks

PubMed Central

Mouw, Ted; Verdery, Ashton M.

2013-01-01

Techniques for sampling from networks have grown into an important area of research across several fields. For sociologists, the possibility of sampling from a network is appealing for two reasons: (1) A network sample can yield substantively interesting data about network structures and social interactions, and (2) it is useful in situations where study populations are difficult or impossible to survey with traditional sampling approaches because of the lack of a sampling frame. Despite its appeal, methodological concerns about the precision and accuracy of network-based sampling methods remain. In particular, recent research has shown that sampling from a network using a random walk based approach such as Respondent Driven Sampling (RDS) can result in high design effects (DE)—the ratio of the sampling variance to the sampling variance of simple random sampling (SRS). A high design effect means that more cases must be collected to achieve the same level of precision as SRS. In this paper we propose an alternative strategy, Network Sampling with Memory (NSM), which collects network data from respondents in order to reduce design effects and, correspondingly, the number of interviews needed to achieve a given level of statistical power. NSM combines a “List” mode, where all individuals on the revealed network list are sampled with the same cumulative probability, with a “Search” mode, which gives priority to bridge nodes connecting the current sample to unexplored parts of the network. We test the relative efficiency of NSM compared to RDS and SRS on 162 school and university networks from Add Health and Facebook that range in size from 110 to 16,278 nodes. The results show that the average design effect for NSM on these 162 networks is 1.16, which is very close to the efficiency of a simple random sample (DE=1), and 98.5% lower than the average DE we observed for RDS. PMID:24159246

Improved Horvitz-Thompson Estimation of Model Parameters from Two-phase Stratified Samples: Applications in Epidemiology

PubMed Central

Breslow, Norman E.; Lumley, Thomas; Ballantyne, Christie M; Chambless, Lloyd E.; Kulich, Michal

2009-01-01

The case-cohort study involves two-phase sampling: simple random sampling from an infinite super-population at phase one and stratified random sampling from a finite cohort at phase two. Standard analyses of case-cohort data involve solution of inverse probability weighted (IPW) estimating equations, with weights determined by the known phase two sampling fractions. The variance of parameter estimates in (semi)parametric models, including the Cox model, is the sum of two terms: (i) the model based variance of the usual estimates that would be calculated if full data were available for the entire cohort; and (ii) the design based variance from IPW estimation of the unknown cohort total of the efficient influence function (IF) contributions. This second variance component may be reduced by adjusting the sampling weights, either by calibration to known cohort totals of auxiliary variables correlated with the IF contributions or by their estimation using these same auxiliary variables. Both adjustment methods are implemented in the R survey package. We derive the limit laws of coefficients estimated using adjusted weights. The asymptotic results suggest practical methods for construction of auxiliary variables that are evaluated by simulation of case-cohort samples from the National Wilms Tumor Study and by log-linear modeling of case-cohort data from the Atherosclerosis Risk in Communities Study. Although not semiparametric efficient, estimators based on adjusted weights may come close to achieving full efficiency within the class of augmented IPW estimators. PMID:20174455

Uncertainty, learning, and the optimal management of wildlife

USGS Publications Warehouse

Williams, B.K.

2001-01-01

Wildlife management is limited by uncontrolled and often unrecognized environmental variation, by limited capabilities to observe and control animal populations, and by a lack of understanding about the biological processes driving population dynamics. In this paper I describe a comprehensive framework for management that includes multiple models and likelihood values to account for structural uncertainty, along with stochastic factors to account for environmental variation, random sampling, and partial controllability. Adaptive optimization is developed in terms of the optimal control of incompletely understood populations, with the expected value of perfect information measuring the potential for improving control through learning. The framework for optimal adaptive control is generalized by including partial observability and non-adaptive, sample-based updating of model likelihoods. Passive adaptive management is derived as a special case of constrained adaptive optimization, representing a potentially efficient suboptimal alternative that nonetheless accounts for structural uncertainty.

How Random Is Social Behaviour? Disentangling Social Complexity through the Study of a Wild House Mouse Population

PubMed Central

Perony, Nicolas; Tessone, Claudio J.; König, Barbara; Schweitzer, Frank

2012-01-01

Out of all the complex phenomena displayed in the behaviour of animal groups, many are thought to be emergent properties of rather simple decisions at the individual level. Some of these phenomena may also be explained by random processes only. Here we investigate to what extent the interaction dynamics of a population of wild house mice (Mus domesticus) in their natural environment can be explained by a simple stochastic model. We first introduce the notion of perceptual landscape, a novel tool used here to describe the utilisation of space by the mouse colony based on the sampling of individuals in discrete locations. We then implement the behavioural assumptions of the perceptual landscape in a multi-agent simulation to verify their accuracy in the reproduction of observed social patterns. We find that many high-level features – with the exception of territoriality – of our behavioural dataset can be accounted for at the population level through the use of this simplified representation. Our findings underline the potential importance of random factors in the apparent complexity of the mice's social structure. These results resonate in the general context of adaptive behaviour versus elementary environmental interactions. PMID:23209394

Assessing differences in groups randomized by recruitment chain in a respondent-driven sample of Seattle-area injection drug users.

PubMed

Burt, Richard D; Thiede, Hanne

2014-11-01

Respondent-driven sampling (RDS) is a form of peer-based study recruitment and analysis that incorporates features designed to limit and adjust for biases in traditional snowball sampling. It is being widely used in studies of hidden populations. We report an empirical evaluation of RDS's consistency and variability, comparing groups recruited contemporaneously, by identical methods and using identical survey instruments. We randomized recruitment chains from the RDS-based 2012 National HIV Behavioral Surveillance survey of injection drug users in the Seattle area into two groups and compared them in terms of sociodemographic characteristics, drug-associated risk behaviors, sexual risk behaviors, human immunodeficiency virus (HIV) status and HIV testing frequency. The two groups differed in five of the 18 variables examined (P ≤ .001): race (e.g., 60% white vs. 47%), gender (52% male vs. 67%), area of residence (32% downtown Seattle vs. 44%), an HIV test in the previous 12 months (51% vs. 38%). The difference in serologic HIV status was particularly pronounced (4% positive vs. 18%). In four further randomizations, differences in one to five variables attained this level of significance, although the specific variables involved differed. We found some material differences between the randomized groups. Although the variability of the present study was less than has been reported in serial RDS surveys, these findings indicate caution in the interpretation of RDS results. Copyright © 2014 Elsevier Inc. All rights reserved.

Prevalence of DSM-5 Autism Spectrum Disorder Among School-Based Children Aged 3-12 Years in Shanghai, China.

PubMed

Jin, Zhijuan; Yang, You; Liu, Shijian; Huang, Hong; Jin, Xingming

2018-02-16

We estimated the prevalence of ASD in a population-based sample comprising children aged 3-12 years (N = 74,252) in Shanghai. This included a high-risk group sampled from special education schools and a low-risk group randomly sampled from general schools. First, we asked parents and then teachers to complete the Social Communication Questionnaire for participating children. Children who screened positive based on both parental and teachers' reports were comprehensively assessed. ASD was identified based on DSM-5 criteria. We identified 711 children as being at-risk for ASD, of which 203 were identified as ASD cases. The prevalence of ASD was 8.3 per 10,000, which is likely an underestimate, given that 81.6% of the children diagnosed with ASD had IQs below 40. This is the first report on the prevalence of ASD according to DSM-5 in China.

Mental disorder and long-term risk of mortality: 41 years of follow-up of a population sample in Stockholm, Sweden.

PubMed

Lundin, A; Modig, K; Halldin, J; Carlsson, A C; Wändell, P; Theobald, H

2016-08-01

An increased mortality risk associated with mental disorder has been reported for patients, but there are few studies are based on random samples with interview-based psychiatric diagnoses. Part of the increased mortality for those with mental disorder may be attributable to worse somatic health or hazardous health behaviour - consequences of the disorder - but somatic health information is commonly lacking in psychiatric samples. This study aims to examine long-term mortality risk for psychiatric diagnoses in a general population sample and to assess mediation by somatic ill health and hazardous health behaviour. We used a double-phase stratified random sample of individuals aged 18-65 in Stockholm County 1970-1971 linked to vital records. First phase sample was 32 186 individuals screened with postal questionnaire and second phase was 1896 individuals (920 men and 976 women) that participated in a full-day examination (participation rate 88%). Baseline examination included both a semi-structured interview with a psychiatrist, with mental disorders set according to the 8th version of the International Classification of Disease (ICD-8), and clinical somatic examination, including measures of body composition (BMI), hypertension, fasting blood glucose, pulmonary function and self-reported tobacco smoking. Information on vital status was obtained from the Total Population Register for the years 1970-2011. Associations with mortality were studied with Cox proportional hazard analyses. A total of 883 deaths occurred among the participants during the 41-year follow-up. Increased mortality rates were found for ICD-8 functional psychoses (hazard ratio, HR = 2.22, 95% confidence interval (95% CI): 1.15-4.30); psycho-organic symptoms (HR = 1.94, 95% CI: 1.31-2.87); depressive neuroses (HR = 1.71, 95% CI: 1.23-2.39); alcohol use disorder (HR = 1.91, 95% CI: 1.40-2.61); drug dependence (HR = 3.71, 95% CI: 1.80-7.65) and psychopathy (HR = 2.88, 95% CI: 1.02-8.16). Non-participants (n = 349) had mortality rates similar to participants (HR = 0.98, 95% CI: 0.81-1.18). In subgroup analyses of those with psychoses, depression or alcohol use disorder, adjusting for the potential mediators smoking and pulmonary function, showed only slight changes in the HRs. This study confirms the increased risk of mortality for several psychiatric diagnoses in follow-up studies on American, Finnish and Swedish population-based samples. Only a small part of the increased mortality hazard was attributable to differences in somatic health or hazardous health behaviour measured at baseline.

Alcohol and Drug Use, Abuse, and Dependence in Urban Areas and Colonias of the Texas-Mexico Border

ERIC Educational Resources Information Center

Wallisch, Lynn S.; Spence, Richard T.

2006-01-01

This study describes the prevalence of alcohol and drug use, abuse, and dependence among adults on the Texas-Mexico border in 2002-2003. The findings are based on survey responses from a random sample of 1,200 adults living in households in three communities: El Paso, a densely populated city in west Texas; the less dense urbanized areas of the…

Estimating the breeding population of long-billed curlew in the United States

USGS Publications Warehouse

Stanley, T.R.; Skagen, S.K.

2007-01-01

Determining population size and long-term trends in population size for species of high concern is a priority of international, national, and regional conservation plans. Long-billed curlews (Numenius americanus) are a species of special concern in North America due to apparent declines in their population. Because long-billed curlews are not adequately monitored by existing programs, we undertook a 2-year study with the goals of 1) determining present long-billed curlew distribution and breeding population size in the United States and 2) providing recommendations for a long-term long-billed curlew monitoring protocol. We selected a stratified random sample of survey routes in 16 western states for sampling in 2004 and 2005, and we analyzed count data from these routes to estimate detection probabilities and abundance. In addition, we evaluated habitat along roadsides to determine how well roadsides represented habitat throughout the sampling units. We estimated there were 164,515 (SE = 42,047) breeding long-billed curlews in 2004, and 109,533 (SE = 31,060) breeding individuals in 2005. These estimates far exceed currently accepted estimates based on expert opinion. We found that habitat along roadsides was representative of long-billed curlew habitat in general. We make recommendations for improving sampling methodology, and we present power curves to provide guidance on minimum sample sizes required to detect trends in abundance.

A pilot randomized controlled trial of a depression and disease management program delivered by phone.

PubMed

Aburizik, Arwa; Dindo, Lilian; Kaboli, Peter; Charlton, Mary; Dawn, Klein; Turvey, Carolyn

2013-11-01

Depression in medically ill patients occurs at twice the rate found in the general population. Though pharmacologic and psychotherapeutic interventions for depression are effective, response to treatment and access to care are barriers for this population. A multidimensional telehealth intervention was designed to focus on these barriers by delivering a phone based intervention that addressed managing one's illness and coping emotionally. Veterans with diabetes, hypertension, or chronic pain and depressive symptoms were randomized to one of three conditions: Usual Care (n=23), Illness Management Only (n=31), or Combined Psychotherapy and Illness Management (n=29). Those randomized to the Combined or Illness Management Only intervention group received 10 phone visits. Veterans in the Combined group received all aspects of the illness management program plus a manualized depression intervention. Subjects completed assessments at baseline, week 5, and 10 to test the main hypothesis that veterans in the Combined condition would have a greater decline in depressive symptoms. The Combined intervention yielded a significant decline in depressive symptoms when compared with Usual Care. However, the there was no significant difference between the Combined and Illness Management Only groups. This is a pilot study with a small sample size relative to a standard randomized controlled trial in psychotherapy. This telephone-based intervention succeeded in reducing depressive symptoms in veterans with chronic illness. It adds to the building evidence base for providing phone-delivered mental health services. © 2013 Elsevier B.V. All rights reserved.

Isonymy structure of four Venezuelan states.

PubMed

Rodríguez-Larralde, A; Barrai, I; Alfonzo, J C

1993-01-01

The isonymy structure of four Venezuelan States-Falcón, Mérida, Nueva Esparta and Yaracuy-was studied using the surnames of the Venezuelan register of electors updated in 1984. The surname distributions of 155 counties were obtained and, for each county, estimates of consanguinity due to random isonymy and Fisher's alpha were calculated. It was shown that for large sample sizes the inverse of Fisher's alpha is identical to the unbiased estimate of within-population random isonymy. A three-dimensional isometric surface plot was obtained for each State, based on the counties' random isonymy estimates. The highest estimates of random consanguinity were found in the States of Nueva Esparta and Mérida, while the lowest were found in Yaracuy. Other microdifferentiation indicators from the same data gave similar results, and an interpretation was attempted, based on the particular economic and geographic characteristics of each State. Four different genetic distances between all possible pairs of counties were calculated within States; geographic distance shows the highest correlations with random isonymy and Euclidean distance, with the exception of the State of Nueva Esparta, where there is no correlation between geographic distance and random isonymy. It was possible to group counties in clusters, from dendrograms based on Euclidean distance. Isonymy clustering was also consistent with socioeconomic and geographic characteristics of the counties.

TNO/Centaurs grouping tested with asteroid data sets

NASA Astrophysics Data System (ADS)

Fulchignoni, M.; Birlan, M.; Barucci, M. A.

2001-11-01

Recently, we have discussed the possible subdivision in few groups of a sample of 22 TNO and Centaurs for which the BVRIJ photometry were available (Barucci et al., 2001, A&A, 371,1150). We obtained this results using the multivariate statistics adopted to define the current asteroid taxonomy, namely the Principal Components Analysis and the G-mode method (Tholen & Barucci, 1989, in ASTEROIDS II). How these methods work with a very small statistical sample as the TNO/Centaurs one? Theoretically, the number of degrees of freedom of the sample is correct. In fact it is 88 in our case and have to be larger then 50 to cope with the requirements of the G-mode. Does the random sampling of the small number of members of a large population contain enough information to reveal some structure in the population? We extracted several samples of 22 asteroids out of a data-base of 86 objects of known taxonomic type for which BVRIJ photometry is available from ECAS (Zellner et al. 1985, ICARUS 61, 355), SMASS II (S.W. Bus, 1999, PhD Thesis, MIT), and the Bell et al. Atlas of the asteroid infrared spectra. The objects constituting the first sample were selected in order to give a good representation of the major asteroid taxonomic classes (at least three samples each class): C,S,D,A, and G. Both methods were able to distinguish all these groups confirming the validity of the adopted methods. The S class is hard to individuate as a consequence of the choice of I and J variables, which imply a lack of information on the absorption band at 1 micron. The other samples were obtained by random choice of the objects. Not all the major groups were well represented (less than three samples per groups), but the general trend of the asteroid taxonomy has been always obtained. We conclude that the quoted grouping of TNO/Centaurs is representative of some physico-chemical structure of the outer solar system small body population.

Statistical uncertainty analysis applied to the DRAGONv4 code lattice calculations and based on JENDL-4 covariance data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernandez-Solis, A.; Demaziere, C.; Ekberg, C.

2012-07-01

In this paper, multi-group microscopic cross-section uncertainty is propagated through the DRAGON (Version 4) lattice code, in order to perform uncertainty analysis on k{infinity} and 2-group homogenized macroscopic cross-sections predictions. A statistical methodology is employed for such purposes, where cross-sections of certain isotopes of various elements belonging to the 172 groups DRAGLIB library format, are considered as normal random variables. This library is based on JENDL-4 data, because JENDL-4 contains the largest amount of isotopic covariance matrixes among the different major nuclear data libraries. The aim is to propagate multi-group nuclide uncertainty by running the DRAGONv4 code 500 times, andmore » to assess the output uncertainty of a test case corresponding to a 17 x 17 PWR fuel assembly segment without poison. The chosen sampling strategy for the current study is Latin Hypercube Sampling (LHS). The quasi-random LHS allows a much better coverage of the input uncertainties than simple random sampling (SRS) because it densely stratifies across the range of each input probability distribution. Output uncertainty assessment is based on the tolerance limits concept, where the sample formed by the code calculations infers to cover 95% of the output population with at least a 95% of confidence. This analysis is the first attempt to propagate parameter uncertainties of modern multi-group libraries, which are used to feed advanced lattice codes that perform state of the art resonant self-shielding calculations such as DRAGONv4. (authors)« less

Mendelian Randomization.

PubMed

Grover, Sandeep; Del Greco M, Fabiola; Stein, Catherine M; Ziegler, Andreas

2017-01-01

Confounding and reverse causality have prevented us from drawing meaningful clinical interpretation even in well-powered observational studies. Confounding may be attributed to our inability to randomize the exposure variable in observational studies. Mendelian randomization (MR) is one approach to overcome confounding. It utilizes one or more genetic polymorphisms as a proxy for the exposure variable of interest. Polymorphisms are randomly distributed in a population, they are static throughout an individual's lifetime, and may thus help in inferring directionality in exposure-outcome associations. Genome-wide association studies (GWAS) or meta-analyses of GWAS are characterized by large sample sizes and the availability of many single nucleotide polymorphisms (SNPs), making GWAS-based MR an attractive approach. GWAS-based MR comes with specific challenges, including multiple causality. Despite shortcomings, it still remains one of the most powerful techniques for inferring causality.With MR still an evolving concept with complex statistical challenges, the literature is relatively scarce in terms of providing working examples incorporating real datasets. In this chapter, we provide a step-by-step guide for causal inference based on the principles of MR with a real dataset using both individual and summary data from unrelated individuals. We suggest best possible practices and give recommendations based on the current literature.

A Portuguese value set for the SF-6D.

PubMed

Ferreira, Lara N; Ferreira, Pedro L; Pereira, Luis N; Brazier, John; Rowen, Donna

2010-08-01

The SF-6D is a preference-based measure of health derived from the SF-36 that can be used for cost-effectiveness analysis using cost-per-quality adjusted life-year analysis. This study seeks to estimate a system weight for the SF-6D for Portugal and to compare the results with the UK system weights. A sample of 55 health states defined by the SF-6D has been valued by a representative random sample of the Portuguese population, stratified by sex and age (n = 140), using the Standard Gamble (SG). Several models are estimated at both the individual and aggregate levels for predicting health-state valuations. Models with main effects, with interaction effects and with the constant forced to unity are presented. Random effects (RE) models are estimated using generalized least squares (GLS) regressions. Generalized estimation equations (GEE) are used to estimate RE models with the constant forced to unity. Estimations at the individual level were performed using 630 health-state valuations. Alternative functional forms are considered to account for the skewed distribution of health-state valuations. The models are analyzed in terms of their coefficients, overall fit, and the ability for predicting the SG-values. The RE models estimated using GLS and through GEE produce significant coefficients, which are robust across model specification. However, there are concerns regarding some inconsistent estimates, and so parsimonious consistent models were estimated. There is evidence of under prediction in some states assigned to poor health. The results are consistent with the UK results. The models estimated provide preference-based quality of life weights for the Portuguese population when health status data have been collected using the SF-36. Although the sample was randomly drowned findings should be treated with caution, given the small sample size, even knowing that they have been estimated at the individual level.

Age, maturation, and population structure of the Humboldt squid Dosidicus gigas off the Peruvian Exclusive Economic Zones

NASA Astrophysics Data System (ADS)

Liu, Bilin; Chen, Xinjun; Chen, Yong; Tian, Siquan; Li, Jianhua; Fang, Zhou; Yang, Mingxia

2013-01-01

Age, maturation and population structure of the Humboldt squid Dosidicus gigas were studied based on random sampling of the Chinese jigging fishery off the Peruvian Exclusive Economic Zones (EEZ) during 2008-2010. Estimated ages ranged from 144 to 633 days, confirming that the squid is a short-lived species with longevity no longer than 2 years. Occurrence of mature females and hatching in each month indicated that Humboldt squid spawned year-round. Back-calculated hatching dates for the samples were from January 22nd, 2008 to April 22nd, 2010 with a peak between January and March. Two size-based and two hatching date-based populations could be defined from mantle length (ML) at maturity and back-calculated hatching dates, respectively. Females matured at a larger size than males, and there was a significant difference in ML at maturity between the two hatching groups ( P <0.05). The waters adjacent to 11°S off the Peruvian EEZ may be a potential spawning ground. This study shows the complexity of the population structure and large variability in key life history parameters in the Humboldt squid off the Peruvian EEZ, which should be considered in the assessment and management of this important resource.

Assessing sample representativeness in randomized controlled trials: application to the National Institute of Drug Abuse Clinical Trials Network.

PubMed

Susukida, Ryoko; Crum, Rosa M; Stuart, Elizabeth A; Ebnesajjad, Cyrus; Mojtabai, Ramin

2016-07-01

To compare the characteristics of individuals participating in randomized controlled trials (RCTs) of treatments of substance use disorder (SUD) with individuals receiving treatment in usual care settings, and to provide a summary quantitative measure of differences between characteristics of these two groups of individuals using propensity score methods. Design Analyses using data from RCT samples from the National Institute of Drug Abuse Clinical Trials Network (CTN) and target populations of patients drawn from the Treatment Episodes Data Set-Admissions (TEDS-A). Settings Multiple clinical trial sites and nation-wide usual SUD treatment settings in the United States. A total of 3592 individuals from 10 CTN samples and 1 602 226 individuals selected from TEDS-A between 2001 and 2009. Measurements The propensity scores for enrolling in the RCTs were computed based on the following nine observable characteristics: sex, race/ethnicity, age, education, employment status, marital status, admission to treatment through criminal justice, intravenous drug use and the number of prior treatments. Findings The proportion of those with ≥ 12 years of education and the proportion of those who had full-time jobs were significantly higher among RCT samples than among target populations (in seven and nine trials, respectively, at P < 0.001). The pooled difference in the mean propensity scores between the RCTs and the target population was 1.54 standard deviations and was statistically significant at P < 0.001. In the United States, individuals recruited into randomized controlled trials of substance use disorder treatments appear to be very different from individuals receiving treatment in usual care settings. Notably, RCT participants tend to have more years of education and a greater likelihood of full-time work compared with people receiving care in usual care settings. © 2016 Society for the Study of Addiction.

Rapid diagnosis of common deletional α-thalassemia in the Chinese population by qPCR based on identical primer homologous fragments.

PubMed

Long, Ju

2016-05-01

In China, -(SEA), -α(3.7) and -α(4.2) are common deletional α-thalassemia alleles. Gap-PCR is the currently used detection method for these alleles, whose disadvantages include time-consuming procedure and increased potential for PCR product contamination. Therefore, this detection method needs to be improved. Based on identical-primer homologous fragments, a qPCR system was developed for deletional α-thalassemia genotyping, which was composed of a group of quantitatively-related primers and their corresponding probes plus two groups of qualitatively-related primers and their corresponding probes. In order to verify the accuracy of the qPCR system, known genotype samples and random samples are employed. The standard curve result demonstrated that designed primers and probes all yielded good amplification efficiency. In the tests of known genotype samples and random samples, sample detection results were consistent with verification results. In detecting αα, -(SEA), -α(3.7) and -α(4.2) alleles, deletional α-thalassemia alleles are accurately detected by this method. In addition, this method is provided with a wider detection range, greater speed and reduced PCR product contamination risk when compared with current common gap-PCR detection reagents. Copyright © 2016 Elsevier B.V. All rights reserved.

Prediction of penicillin resistance in Staphylococcus aureus isolates from dairy cows with mastitis, based on prior test results.

PubMed

Grinberg, A; Lopez-Villalobos, N; Lawrence, K; Nulsen, M

2005-10-01

To gauge how well prior laboratory test results predict in vitro penicillin resistance of Staphylococcus aureus isolates from dairy cows with mastitis. Population-based data on the farm of origin (n=79), genotype based on pulsed-field gel electrophoresis (PFGE) results, and the penicillin-resistance status of Staph. aureus isolates (n=115) from milk samples collected from dairy cows with mastitis submitted to two diagnostic laboratories over a 6-month period were used. Data were mined stochastically using the all-possible-pairs method, binomial modelling and bootstrap simulation, to test whether prior test results enhance the accuracy of prediction of penicillin resistance on farms. Of all Staph. aureus isolates tested, 38% were penicillin resistant. A significant aggregation of penicillin-resistance status was evident within farms. The probability of random pairs of isolates from the same farm having the same penicillin-resistance status was 76%, compared with 53% for random pairings of samples across all farms. Thus, the resistance status of randomly selected isolates was 1.43 times more likely to correctly predict the status of other isolates from the same farm than the random population pairwise concordance probability (p=0.011). This effect was likely due to the clonal relationship of isolates within farms, as the predictive fraction attributable to prior test results was close to nil when the effect of within-farm clonal infections was withdrawn from the model. Knowledge of the penicillin-resistance status of a prior Staph. aureus isolate significantly enhanced the predictive capability of other isolates from the same farm. In the time and space frame of this study, clinicians using previous information from a farm would have more accurately predicted the penicillin-resistance status of an isolate than they would by chance alone on farms infected with clonal Staph. aureus isolates, but not on farms infected with highly genetically heterogeneous bacterial strains.

Smoothing the redshift distributions of random samples for the baryon acoustic oscillations: applications to the SDSS-III BOSS DR12 and QPM mock samples

NASA Astrophysics Data System (ADS)

Wang, Shao-Jiang; Guo, Qi; Cai, Rong-Gen

2017-12-01

We investigate the impact of different redshift distributions of random samples on the baryon acoustic oscillations (BAO) measurements of D_V(z)r_d^fid/r_d from the two-point correlation functions of galaxies in the Data Release 12 of the Baryon Oscillation Spectroscopic Survey (BOSS). Big surveys, such as BOSS, usually assign redshifts to the random samples by randomly drawing values from the measured redshift distributions of the data, which would necessarily introduce fiducial signals of fluctuations into the random samples, weakening the signals of BAO, if the cosmic variance cannot be ignored. We propose a smooth function of redshift distribution that fits the data well to populate the random galaxy samples. The resulting cosmological parameters match the input parameters of the mock catalogue very well. The significance of BAO signals has been improved by 0.33σ for a low-redshift sample and by 0.03σ for a constant-stellar-mass sample, though the absolute values do not change significantly. Given the precision of the measurements of current cosmological parameters, it would be appreciated for the future improvements on the measurements of galaxy clustering.

Prevalence of smoking among bar workers prior to the Republic of Ireland smokefree workplace legislation.

PubMed

Mullally, B J; Greiner, B A; Allwright, S; Paul, G; Perry, I J

2008-12-01

This study establishes baseline prevalence of smoking and cigarette consumption among Cork bar workers prior to the Republic of Ireland's (ROI) smokefree workplace legislation and compares gender- and age-specific smoking rates and estimates the adjusted odds of being a smoker for Cork bar workers relative to the general population. Cross-sectional random sample of bar workers in Cork city and cross-sectional random telephone survey of the general population were conducted prior to the smokefree legislation. Self reported smoking prevalence among Cork bar workers (n = 129) was 54% (58% using cotinine-validated measures), with particularly high rates in women (70%) and 18-28 years old (72%). Within the ROI (n = 1,240) sub-sample rates were substantially lower at 28%. Bar workers were twice as likely to be smokers as the general population sub-sample (OR = 2.15). Cork bar workers constitute an occupational group with an extremely high smoking prevalence.

[Identification and sampling of people with migration background for epidemiological studies in Germany].

PubMed

Reiss, K; Makarova, N; Spallek, J; Zeeb, H; Razum, O

2013-06-01

In 2009, 19.6% of the population of Germany either had migrated themselves or were the offspring of people with migration experience. Migrants differ from the autochthonous German population in terms of health status, health awareness and health behaviour. To further investigate the health situation of migrants in Germany, epidemiological studies are needed. Such studies can employ existing databases which provide detailed information on migration status. Otherwise, onomastic or toponomastic procedures can be applied to identify people with migration background. If migrants have to be recruited into an epidemiological study, this can be done register-based (e. g., data from registration offices or telephone lists), based on residential location (random-route or random-walk procedure), via snowball sampling (e. g., through key persons) or via settings (e. g., school entry examination). An oversampling of people with migration background is not sufficient to avoid systematic bias in the sample due to non-participation. Additional measures have to be taken to increase access and raise participation rates. Personal contacting, multilingual instruments, multilingual interviewers and extensive public relations increase access and willingness to participate. Empirical evidence on 'successful' recruitment strategies for studies with migrants is still lacking in epidemiology and health sciences in Germany. The choice of the recruitment strategy as well as the measures to raise accessibility and willingness to participate depend on the available resources, the research question and the specific migrant target group. © Georg Thieme Verlag KG Stuttgart · New York.

Evaluating diagnosis-based case-mix measures: how well do they apply to the VA population?

PubMed

Rosen, A K; Loveland, S; Anderson, J J; Rothendler, J A; Hankin, C S; Rakovski, C C; Moskowitz, M A; Berlowitz, D R

2001-07-01

Diagnosis-based case-mix measures are increasingly used for provider profiling, resource allocation, and capitation rate setting. Measures developed in one setting may not adequately capture the disease burden in other settings. To examine the feasibility of adapting two such measures, Adjusted Clinical Groups (ACGs) and Diagnostic Cost Groups (DCGs), to the Department of Veterans Affairs (VA) population. A 60% random sample of veterans who used health care services during FY 1997 was obtained from VA inpatient and outpatient administrative databases. A split-sample technique was used to obtain a 40% sample (n = 1,046,803) for development and a 20% sample (n = 524,461) for validation. Concurrent ACG and DCG risk adjustment models, using 1997 diagnoses and demographics to predict FY 1997 utilization (ambulatory provider encounters, and service days-the sum of a patient's inpatient and outpatient visit days), were fitted and cross-validated. Patients were classified into groupings that indicated a population with multiple psychiatric and medical diseases. Model R-squares explained between 6% and 32% of the variation in service utilization. Although reparameterized models did better in predicting utilization than models with external weights, none of the models was adequate in characterizing the entire population. For predicting service days, DCGs were superior to ACGs in most categories, whereas ACGs did better at discriminating among veterans who had the lowest utilization. Although "off-the-shelf" case-mix measures perform moderately well when applied to another setting, modifications may be required to accurately characterize a population's disease burden with respect to the resource needs of all patients.

Drivers of Disparity: Differences in Socially-Based Risk Factors of Self-injurious and Suicidal Behaviors Among Sexual Minority College Students

PubMed Central

Blosnich, John; Bossarte, Robert

2012-01-01

Lesbian, gay, and bisexual (i.e., sexual minority) populations have increased prevalence of both self-injurious and suicidal behaviors, but reasons for these disparities are poorly understood. Objective To test the association between socially-based stressors (e.g., victimization, discrimination) and self-injurious behavior, suicide ideation, and suicide attempt. Participants A national sample of college-attending 18- to 24-year-olds. Methods Random or census samples from post-secondary educational institutions that administered the National College Health Assessment during the Fall 2008 and Spring 2009 semesters. Results Sexual minorities reported more socially-based stressors than heterosexuals. Bisexuals exhibited greatest prevalence of self-injurious and suicidal behaviors. In adjusted models, intimate partner violence was most consistently associated with self-injurious behaviros. Conclusions Sexual minorities' elevated risks of self-injurious and suicidal behaviors may stem from higher exposure to socially-based stressors. Within-group differences among sexual minorities offer insight to specific risk factors that may contribute to elevated self-injurious and suicidal behaviors in sexual minority populations. PMID:22316411

Determining Individual Variation in Growth and Its Implication for Life-History and Population Processes Using the Empirical Bayes Method

PubMed Central

Vincenzi, Simone; Mangel, Marc; Crivelli, Alain J.; Munch, Stephan; Skaug, Hans J.

2014-01-01

The differences in demographic and life-history processes between organisms living in the same population have important consequences for ecological and evolutionary dynamics. Modern statistical and computational methods allow the investigation of individual and shared (among homogeneous groups) determinants of the observed variation in growth. We use an Empirical Bayes approach to estimate individual and shared variation in somatic growth using a von Bertalanffy growth model with random effects. To illustrate the power and generality of the method, we consider two populations of marble trout Salmo marmoratus living in Slovenian streams, where individually tagged fish have been sampled for more than 15 years. We use year-of-birth cohort, population density during the first year of life, and individual random effects as potential predictors of the von Bertalanffy growth function's parameters k (rate of growth) and (asymptotic size). Our results showed that size ranks were largely maintained throughout marble trout lifetime in both populations. According to the Akaike Information Criterion (AIC), the best models showed different growth patterns for year-of-birth cohorts as well as the existence of substantial individual variation in growth trajectories after accounting for the cohort effect. For both populations, models including density during the first year of life showed that growth tended to decrease with increasing population density early in life. Model validation showed that predictions of individual growth trajectories using the random-effects model were more accurate than predictions based on mean size-at-age of fish. PMID:25211603

Introductory Statistics Students' Conceptual Understanding of Study Design and Conclusions

NASA Astrophysics Data System (ADS)

Fry, Elizabeth Brondos

Recommended learning goals for students in introductory statistics courses include the ability to recognize and explain the key role of randomness in designing studies and in drawing conclusions from those studies involving generalizations to a population or causal claims (GAISE College Report ASA Revision Committee, 2016). The purpose of this study was to explore introductory statistics students' understanding of the distinct roles that random sampling and random assignment play in study design and the conclusions that can be made from each. A study design unit lasting two and a half weeks was designed and implemented in four sections of an undergraduate introductory statistics course based on modeling and simulation. The research question that this study attempted to answer is: How does introductory statistics students' conceptual understanding of study design and conclusions (in particular, unbiased estimation and establishing causation) change after participating in a learning intervention designed to promote conceptual change in these areas? In order to answer this research question, a forced-choice assessment called the Inferences from Design Assessment (IDEA) was developed as a pretest and posttest, along with two open-ended assignments, a group quiz and a lab assignment. Quantitative analysis of IDEA results and qualitative analysis of the group quiz and lab assignment revealed that overall, students' mastery of study design concepts significantly increased after the unit, and the great majority of students successfully made the appropriate connections between random sampling and generalization, and between random assignment and causal claims. However, a small, but noticeable portion of students continued to demonstrate misunderstandings, such as confusion between random sampling and random assignment.

Differential expression analysis for RNAseq using Poisson mixed models

PubMed Central

Sun, Shiquan; Hood, Michelle; Scott, Laura; Peng, Qinke; Mukherjee, Sayan; Tung, Jenny

2017-01-01

Abstract Identifying differentially expressed (DE) genes from RNA sequencing (RNAseq) studies is among the most common analyses in genomics. However, RNAseq DE analysis presents several statistical and computational challenges, including over-dispersed read counts and, in some settings, sample non-independence. Previous count-based methods rely on simple hierarchical Poisson models (e.g. negative binomial) to model independent over-dispersion, but do not account for sample non-independence due to relatedness, population structure and/or hidden confounders. Here, we present a Poisson mixed model with two random effects terms that account for both independent over-dispersion and sample non-independence. We also develop a scalable sampling-based inference algorithm using a latent variable representation of the Poisson distribution. With simulations, we show that our method properly controls for type I error and is generally more powerful than other widely used approaches, except in small samples (n <15) with other unfavorable properties (e.g. small effect sizes). We also apply our method to three real datasets that contain related individuals, population stratification or hidden confounders. Our results show that our method increases power in all three data compared to other approaches, though the power gain is smallest in the smallest sample (n = 6). Our method is implemented in MACAU, freely available at www.xzlab.org/software.html. PMID:28369632

Estimating the Size of a Large Network and its Communities from a Random Sample

PubMed Central

Chen, Lin; Karbasi, Amin; Crawford, Forrest W.

2017-01-01

Most real-world networks are too large to be measured or studied directly and there is substantial interest in estimating global network properties from smaller sub-samples. One of the most important global properties is the number of vertices/nodes in the network. Estimating the number of vertices in a large network is a major challenge in computer science, epidemiology, demography, and intelligence analysis. In this paper we consider a population random graph G = (V, E) from the stochastic block model (SBM) with K communities/blocks. A sample is obtained by randomly choosing a subset W ⊆ V and letting G(W) be the induced subgraph in G of the vertices in W. In addition to G(W), we observe the total degree of each sampled vertex and its block membership. Given this partial information, we propose an efficient PopULation Size Estimation algorithm, called PULSE, that accurately estimates the size of the whole population as well as the size of each community. To support our theoretical analysis, we perform an exhaustive set of experiments to study the effects of sample size, K, and SBM model parameters on the accuracy of the estimates. The experimental results also demonstrate that PULSE significantly outperforms a widely-used method called the network scale-up estimator in a wide variety of scenarios. PMID:28867924

Estimating the Size of a Large Network and its Communities from a Random Sample.

PubMed

Chen, Lin; Karbasi, Amin; Crawford, Forrest W

2016-01-01

Most real-world networks are too large to be measured or studied directly and there is substantial interest in estimating global network properties from smaller sub-samples. One of the most important global properties is the number of vertices/nodes in the network. Estimating the number of vertices in a large network is a major challenge in computer science, epidemiology, demography, and intelligence analysis. In this paper we consider a population random graph G = ( V, E ) from the stochastic block model (SBM) with K communities/blocks. A sample is obtained by randomly choosing a subset W ⊆ V and letting G ( W ) be the induced subgraph in G of the vertices in W . In addition to G ( W ), we observe the total degree of each sampled vertex and its block membership. Given this partial information, we propose an efficient PopULation Size Estimation algorithm, called PULSE, that accurately estimates the size of the whole population as well as the size of each community. To support our theoretical analysis, we perform an exhaustive set of experiments to study the effects of sample size, K , and SBM model parameters on the accuracy of the estimates. The experimental results also demonstrate that PULSE significantly outperforms a widely-used method called the network scale-up estimator in a wide variety of scenarios.

Are most samples of animals systematically biased? Consistent individual trait differences bias samples despite random sampling.

PubMed

Biro, Peter A

2013-02-01

Sampling animals from the wild for study is something nearly every biologist has done, but despite our best efforts to obtain random samples of animals, 'hidden' trait biases may still exist. For example, consistent behavioral traits can affect trappability/catchability, independent of obvious factors such as size and gender, and these traits are often correlated with other repeatable physiological and/or life history traits. If so, systematic sampling bias may exist for any of these traits. The extent to which this is a problem, of course, depends on the magnitude of bias, which is presently unknown because the underlying trait distributions in populations are usually unknown, or unknowable. Indeed, our present knowledge about sampling bias comes from samples (not complete population censuses), which can possess bias to begin with. I had the unique opportunity to create naturalized populations of fish by seeding each of four small fishless lakes with equal densities of slow-, intermediate-, and fast-growing fish. Using sampling methods that are not size-selective, I observed that fast-growing fish were up to two-times more likely to be sampled than slower-growing fish. This indicates substantial and systematic bias with respect to an important life history trait (growth rate). If correlations between behavioral, physiological and life-history traits are as widespread as the literature suggests, then many animal samples may be systematically biased with respect to these traits (e.g., when collecting animals for laboratory use), and affect our inferences about population structure and abundance. I conclude with a discussion on ways to minimize sampling bias for particular physiological/behavioral/life-history types within animal populations.

Physiogenomic analysis of the Puerto Rican population

PubMed Central

Ruaño, Gualberto; Duconge, Jorge; Windemuth, Andreas; Cadilla, Carmen L; Kocherla, Mohan; Villagra, David; Renta, Jessica; Holford, Theodore; Santiago-Borrero, Pedro J

2009-01-01

Aims Admixture in the population of the island of Puerto Rico is of general interest with regards to pharmacogenetics to develop comprehensive strategies for personalized healthcare in Latin Americans. This research was aimed at determining the frequencies of SNPs in key physiological, pharmacological and biochemical genes to infer population structure and ancestry in the Puerto Rican population. Materials & methods A noninterventional, cross-sectional, retrospective study design was implemented following a controlled, stratified-by-region, random sampling protocol. The sample was based on birthrates in each region of the island of Puerto Rico, according to the 2004 National Birth Registry. Genomic DNA samples from 100 newborns were obtained from the Puerto Rico Newborn Screening Program in dried-blood spot cards. Genotyping using a physiogenomic array was performed for 332 SNPs from 196 cardiometabolic and neuroendocrine genes. Population structure was examined using a Bayesian clustering approach as well as by allelic dissimilarity as a measure of allele sharing. Results The Puerto Rican sample was found to be broadly heterogeneous. We observed three main clusters in the population, which we hypothesize to reflect the historical admixture in the Puerto Rican population from Amerindian, African and European ancestors. We present evidence for this interpretation by comparing allele frequencies for the three clusters with those for the same SNPs available from the International HapMap project for Asian, African and European populations. Conclusion Our results demonstrate that population analysis can be performed with a physiogenomic array of cardiometabolic and neuroendocrine genes to facilitate the translation of genome diversity into personalized medicine. PMID:19374515

Generalizability of findings from randomized controlled trials: application to the National Institute of Drug Abuse Clinical Trials Network.

PubMed

Susukida, Ryoko; Crum, Rosa M; Ebnesajjad, Cyrus; Stuart, Elizabeth A; Mojtabai, Ramin

2017-07-01

To compare randomized controlled trial (RCT) sample treatment effects with the population effects of substance use disorder (SUD) treatment. Statistical weighting was used to re-compute the effects from 10 RCTs such that the participants in the trials had characteristics that resembled those of patients in the target populations. Multi-site RCTs and usual SUD treatment settings in the United States. A total of 3592 patients in 10 RCTs and 1 602 226 patients from usual SUD treatment settings between 2001 and 2009. Three outcomes of SUD treatment were examined: retention, urine toxicology and abstinence. We weighted the RCT sample treatment effects using propensity scores representing the conditional probability of participating in RCTs. Weighting the samples changed the significance of estimated sample treatment effects. Most commonly, positive effects of trials became statistically non-significant after weighting (three trials for retention and urine toxicology and one trial for abstinence); also, non-significant effects became significantly positive (one trial for abstinence) and significantly negative effects became non-significant (two trials for abstinence). There was suggestive evidence of treatment effect heterogeneity in subgroups that are under- or over-represented in the trials, some of which were consistent with the differences in average treatment effects between weighted and unweighted results. The findings of randomized controlled trials (RCTs) for substance use disorder treatment do not appear to be directly generalizable to target populations when the RCT samples do not reflect adequately the target populations and there is treatment effect heterogeneity across patient subgroups. © 2017 Society for the Study of Addiction.

Sequential time interleaved random equivalent sampling for repetitive signal.

PubMed

Zhao, Yijiu; Liu, Jingjing

2016-12-01

Compressed sensing (CS) based sampling techniques exhibit many advantages over other existing approaches for sparse signal spectrum sensing; they are also incorporated into non-uniform sampling signal reconstruction to improve the efficiency, such as random equivalent sampling (RES). However, in CS based RES, only one sample of each acquisition is considered in the signal reconstruction stage, and it will result in more acquisition runs and longer sampling time. In this paper, a sampling sequence is taken in each RES acquisition run, and the corresponding block measurement matrix is constructed using a Whittaker-Shannon interpolation formula. All the block matrices are combined into an equivalent measurement matrix with respect to all sampling sequences. We implemented the proposed approach with a multi-cores analog-to-digital converter (ADC), whose ADC cores are time interleaved. A prototype realization of this proposed CS based sequential random equivalent sampling method has been developed. It is able to capture an analog waveform at an equivalent sampling rate of 40 GHz while sampled at 1 GHz physically. Experiments indicate that, for a sparse signal, the proposed CS based sequential random equivalent sampling exhibits high efficiency.

A comparison of respondent-driven and venue-based sampling of female sex workers in Liuzhou, China

PubMed Central

Weir, Sharon S; Merli, M Giovanna; Li, Jing; Gandhi, Anisha D; Neely, William W; Edwards, Jessie K; Suchindran, Chirayath M; Henderson, Gail E; Chen, Xiang-Sheng

2012-01-01

Objectives To compare two methods for sampling female sex workers (FSWs) for bio-behavioural surveillance. We compared the populations of sex workers recruited by the venue-based Priorities for Local AIDS Control Efforts (PLACE) method and a concurrently implemented network-based sampling method, respondent-driven sampling (RDS), in Liuzhou, China. Methods For the PLACE protocol, all female workers at a stratified random sample of venues identified as places where people meet new sexual partners were interviewed and tested for syphilis. Female workers who reported sex work in the past 4 weeks were categorised as FSWs. RDS used peer recruitment and chain referral to obtain a sample of FSWs. Data were collected between October 2009 and January 2010. We compared the socio-demographic characteristics and the percentage with a positive syphilis test of FSWs recruited by PLACE and RDS. Results The prevalence of a positive syphilis test was 24% among FSWs recruited by PLACE and 8.5% among those recruited by RDS and tested (prevalence ratio 3.3; 95% CI 1.5 to 7.2). Socio-demographic characteristics (age, residence and monthly income) also varied by sampling method. PLACE recruited fewer FSWs than RDS (161 vs 583), was more labour-intensive and had difficulty gaining access to some venues. RDS was more likely to recruit from areas near the RDS office and from large low prevalence entertainment venues. Conclusions Surveillance protocols using different sampling methods can obtain different estimates of prevalence and population characteristics. Venue-based and network-based methods each have strengths and limitations reflecting differences in design and assumptions. We recommend that more research be conducted on measuring bias in bio-behavioural surveillance. PMID:23172350

Community-Based Evaluation of PMTCT Uptake in Nyanza Province, Kenya

PubMed Central

Kohler, Pamela K.; Okanda, John; Kinuthia, John; Mills, Lisa A.; Olilo, George; Odhiambo, Frank; Laserson, Kayla F.; Zierler, Brenda; Voss, Joachim; John-Stewart, Grace

2014-01-01

Introduction Facility-based assessments of prevention of mother-to-child HIV transmission (PMTCT) programs may overestimate population coverage. There are few community-based studies that evaluate PMTCT coverage and uptake. Methods During 2011, a cross-sectional community survey among women who gave birth in the prior year was performed using the KEMRI-CDC Health and Demographic Surveillance System in Western Kenya. A random sample (n = 405) and a sample of women known to be HIV-positive through previous home-based testing (n = 247) were enrolled. Rates and correlates of uptake of antenatal care (ANC), HIV-testing, and antiretrovirals (ARVs) were determined. Results Among 405 women in the random sample, 379 (94%) reported accessing ANC, most of whom (87%) were HIV tested. Uptake of HIV testing was associated with employment, higher socioeconomic status, and partner HIV testing. Among 247 known HIV-positive women, 173 (70%) self-disclosed their HIV status. Among 216 self-reported HIV-positive women (including 43 from the random sample), 82% took PMTCT ARVs, with 54% completing the full antenatal, peripartum, and postpartum course. Maternal ARV use was associated with more ANC visits and having an HIV tested partner. ARV use during delivery was lowest (62%) and associated with facility delivery. Eighty percent of HIV infected women reported having their infant HIV tested, 11% of whom reported their child was HIV infected, 76% uninfected, 6% declined to say, 7% did not recall; 79% of infected children were reportedly receiving HIV care and treatment. Conclusions Community-based assessments provide data that complements clinic-based PMTCT evaluations. In this survey, antenatal HIV test uptake was high; most HIV infected women received ARVs, though many women did not self-disclose HIV status to field team. Community-driven strategies that encourage early ANC, partner involvement, and skilled delivery, and provide PMTCT education, may facilitate further reductions in vertical transmission. PMID:25360758

Access and completion of a Web-based treatment in a population-based sample of tornado-affected adolescents.

PubMed

Price, Matthew; Yuen, Erica K; Davidson, Tatiana M; Hubel, Grace; Ruggiero, Kenneth J

2015-08-01

Although Web-based treatments have significant potential to assess and treat difficult-to-reach populations, such as trauma-exposed adolescents, the extent that such treatments are accessed and used is unclear. The present study evaluated the proportion of adolescents who accessed and completed a Web-based treatment for postdisaster mental health symptoms. Correlates of access and completion were examined. A sample of 2,000 adolescents living in tornado-affected communities was assessed via structured telephone interview and invited to a Web-based treatment. The modular treatment addressed symptoms of posttraumatic stress disorder, depression, and alcohol and tobacco use. Participants were randomized to experimental or control conditions after accessing the site. Overall access for the intervention was 35.8%. Module completion for those who accessed ranged from 52.8% to 85.6%. Adolescents with parents who used the Internet to obtain health-related information were more likely to access the treatment. Adolescent males were less likely to access the treatment. Future work is needed to identify strategies to further increase the reach of Web-based treatments to provide clinical services in a postdisaster context. (c) 2015 APA, all rights reserved).

Access and Completion of a Web-Based Treatment in a Population-Based Sample of Tornado-Affected Adolescents

PubMed Central

Price, Matthew; Yuen, Erica; Davidson, Tatiana M.; Hubel, Grace; Ruggiero, Kenneth J.

2015-01-01

Although web-based treatments have significant potential to assess and treat difficult to reach populations, such as trauma-exposed adolescents, the extent that such treatments are accessed and used is unclear. The present study evaluated the proportion of adolescents who accessed and completed a web-based treatment for post-disaster mental health symptoms. Correlates of access and completion were examined. A sample of 2,000 adolescents living in tornado-affected communities was assessed via structured telephone interview and invited to a web-based treatment. The modular treatment addressed symptoms of PTSD, depression, and alcohol and tobacco use. Participants were randomized to experimental or control conditions after accessing the site. Overall access for the intervention was 35.8%. Module completion for those who accessed ranged from 52.8% to 85.6%. Adolescents with parents who used the Internet to obtain health-related information were more likely to access the treatment. Adolescent males were less likely to access the treatment. Future work is needed to identify strategies to further increase the reach of web-based treatments to provide clinical services in a post-disaster context. PMID:25622071

Colonoscopy screening for colorectal cancer: the outcomes of two recruitment methods.

PubMed

Corbett, Mike; Chambers, Sharon L; Shadbolt, Bruce; Hillman, Lybus C; Taupin, Doug

2004-10-18

To determine the response to colorectal cancer (CRC) screening by colonoscopy, through direct invitation or through invitation by general practitioners. Two-way comparison of randomised population sampling versus cluster sampling of a representative general practice population in the Australian Capital Territory, May 2002 to January 2004. Invitation to screen, assessment for eligibility, interview, and colonoscopy. 881 subjects aged 55-74 years were invited to screen: 520 from the electoral roll (ER) sample and 361 from the general practice (GP) cluster sample. Response rate, participation rate, and rate of adenomatous polyps in the screened group. Participation was similar in the ER arm (35.1%; 95% CI, 30.2%-40.3%) and the GP arm (40.1%; 95% CI, 29.2%-51.0%) after correcting for ineligibility, which was higher in the ER arm. Superior eligibility in the GP arm was offset by the labour of manual record review. Response rates after two invitations were similar for the two groups (ER arm: 78.8%; 95% CI, 75.1%-82.1%; GP arm: 81.7%; 95% CI, 73.8%-89.6%). Overall, 53.4% ineligibility arose from having a colonoscopy in the past 10 years (ER arm, 98/178; GP arm, 42/84). Of 231 colonoscopies performed, 229 were complete, with 32% of subjects screened having adenomatous polyps. Colonoscopy-based CRC screening yields similar response and participation rates with either random population sampling or general practice cluster sampling, with population sampling through the electoral roll providing greater ease of recruitment.

Healthy Learning Mind - a school-based mindfulness and relaxation program: a study protocol for a cluster randomized controlled trial.

PubMed

Volanen, Salla-Maarit; Lassander, Maarit; Hankonen, Nelli; Santalahti, Päivi; Hintsanen, Mirka; Simonsen, Nina; Raevuori, Anu; Mullola, Sari; Vahlberg, Tero; But, Anna; Suominen, Sakari

2016-07-11

Mindfulness has shown positive effects on mental health, mental capacity and well-being among adult population. Among children and adolescents, previous research on the effectiveness of mindfulness interventions on health and well-being has shown promising results, but studies with methodologically sound designs have been called for. Few intervention studies in this population have compared the effectiveness of mindfulness programs to alternative intervention programs with adequate sample sizes. Our primary aim is to explore the effectiveness of a school-based mindfulness intervention program compared to a standard relaxation program among a non-clinical children and adolescent sample, and a non-treatment control group in school context. In this study, we systematically examine the effects of mindfulness intervention on mental well-being (primary outcomes being resilience; existence/absence of depressive symptoms; experienced psychological strengths and difficulties), cognitive functions, psychophysiological responses, academic achievements, and motivational determinants of practicing mindfulness. The design is a cluster randomized controlled trial with three arms (mindfulness intervention group, active control group, non-treatment group) and the sample includes 59 Finnish schools and approx. 3 000 students aged 12-15 years. Intervention consists of nine mindfulness based lessons, 45 mins per week, for 9 weeks, the dose being identical in active control group receiving standard relaxation program called Relax. The programs are delivered by 14 educated facilitators. Students, their teachers and parents will fill-in the research questionnaires before and after the intervention, and they will all be followed up 6 months after baseline. Additionally, students will be followed 12 months after baseline. For longer follow-up, consent to linking the data to the main health registers has been asked from students and their parents. The present study examines systematically the effectiveness of a school-based mindfulness program compared to a standard relaxation program, and a non-treatment control group. A strength of the current study lies in its methodologically rigorous, randomized controlled study design, which allows novel evidence on the effectiveness of mindfulness over and above a standard relaxation program. ISRCTN18642659 . Retrospectively registered 13 October 2015.

The effectiveness of snow cube throwing learning model based on exploration

NASA Astrophysics Data System (ADS)

Sari, Nenden Mutiara

2017-08-01

This study aimed to know the effectiveness of Snow Cube Throwing (SCT) and Cooperative Model in Exploration-Based Math Learning in terms of the time required to complete the teaching materials and student engagement. This study was quasi-experimental research was conducted at SMPN 5 Cimahi, Indonesia. All student in grade VIII SMPN 5 Cimahi which consists of 382 students is used as population. The sample consists of two classes which had been chosen randomly with purposive sampling. First experiment class consists of 38 students and the second experiment class consists of 38 students. Observation sheet was used to observe the time required to complete the teaching materials and record the number of students involved in each meeting. The data obtained was analyzed by independent sample-t test and used the chart. The results of this study: SCT learning model based on exploration are more effective than cooperative learning models based on exploration in terms of the time required to complete teaching materials based on exploration and student engagement.

Genetic structure of Mexican Mestizos with type 2 diabetes mellitus based on three STR loci.

PubMed

Cerda-Flores, Ricardo M; Rivera-Prieto, Roxana A; Pereyra-Alférez, Benito; Calderón-Garcidueñas, Ana L; Barrera-Saldaña, Hugo A; Gallardo-Blanco, Hugo L; Ortiz-López, Rocío; Flores-Peña, Yolanda; Cárdenas-Villarreal, Velia M; Rivas, Fernando; Figueroa, Andrés; Kshatriya, Gautam

2013-08-01

The aims of this population genetics study were: 1) to ascertain whether Mexicans with type 2 diabetes mellitus (DM) were genetically homogeneous and 2) to compare the genetic structure of this selected population with the previously reported data of four random populations (Nuevo León, Hispanics, Chihuahua, and Central Region of Mexico). A sample of 103 unrelated individuals with DM and whose 4 grandparents were born in five zones of Mexico was interviewed in 32 Medical Units in the Mexican Institute of Social Security (IMSS). The non-coding STRs D16S539, D7S820, and D13S317 were analyzed. Genotype distribution was in agreement with Hardy-Weinberg expectations for all three markers. Allele frequencies were found to be similar between the selected population and the four random populations. Gene diversity analysis suggested that more than 99.57% of the total gene diversity could be attributed to variation between individuals within the population and 0.43% between the populations. According to the present and previous studies using molecular and non-molecular nuclear DNA markers not associated with any disease, the Mexican Mestizo population is found to be genetically homogeneous and therefore the genetic causes of DM are less heterogeneous, thereby simplifying genetic epidemiological studies as has been found in a previous study with the same design in Mexican women with breast cancer. Published by Elsevier B.V.

A Mainly Circum-Mediterranean Origin for West Eurasian and North African mtDNAs in Puerto Rico with Strong Contributions from the Canary Islands and West Africa.

PubMed

Díaz-Zabala, Héctor J; Nieves-Colón, María A; Martínez-Cruzado, Juan C

2017-04-01

Maternal lineages of West Eurasian and North African origin account for 11.5% of total mitochondrial ancestry in Puerto Rico. Historical sources suggest that this ancestry arrived mostly from European migrations that took place during the four centuries of the Spanish colonization of Puerto Rico. This study analyzed 101 mitochondrial control region sequences and diagnostic coding region variants from a sample set randomly and systematically selected using a census-based sampling frame to be representative of the Puerto Rican population, with the goal of defining West Eurasian-North African maternal clades and estimating their possible geographical origin. Median-joining haplotype networks were constructed using hypervariable regions 1 and 2 sequences from various reference populations in search of shared haplotypes. A posterior probability analysis was performed to estimate the percentage of possible origins across wide geographic regions for the entire sample set and for the most common haplogroups on the island. Principal component analyses were conducted to place the Puerto Rican mtDNA set within the variation present among all reference populations. Our study shows that up to 38% of West Eurasian and North African mitochondrial ancestry in Puerto Rico most likely migrated from the Canary Islands. However, most of those haplotypes had previously migrated to the Canary Islands from elsewhere, and there are substantial contributions from various populations across the circum-Mediterranean region and from West African populations related to the modern Wolof and Serer peoples from Senegal and the nomad Fulani who extend up to Cameroon. In conclusion, the West Eurasian mitochondrial ancestry in Puerto Ricans is geographically diverse. However, haplotype diversity seems to be low, and frequencies have been shaped by population bottlenecks, migration waves, and random genetic drift. Consequently, approximately 47% of mtDNAs of West Eurasian and North African ancestry in Puerto Rico probably arrived early in its colonial history.

SAS procedures for designing and analyzing sample surveys

USGS Publications Warehouse

Stafford, Joshua D.; Reinecke, Kenneth J.; Kaminski, Richard M.

2003-01-01

Complex surveys often are necessary to estimate occurrence (or distribution), density, and abundance of plants and animals for purposes of re-search and conservation. Most scientists are familiar with simple random sampling, where sample units are selected from a population of interest (sampling frame) with equal probability. However, the goal of ecological surveys often is to make inferences about populations over large or complex spatial areas where organisms are not homogeneously distributed or sampling frames are in-convenient or impossible to construct. Candidate sampling strategies for such complex surveys include stratified,multistage, and adaptive sampling (Thompson 1992, Buckland 1994).

Accounting for randomness in measurement and sampling in studying cancer cell population dynamics.

PubMed

Ghavami, Siavash; Wolkenhauer, Olaf; Lahouti, Farshad; Ullah, Mukhtar; Linnebacher, Michael

2014-10-01

Knowing the expected temporal evolution of the proportion of different cell types in sample tissues gives an indication about the progression of the disease and its possible response to drugs. Such systems have been modelled using Markov processes. We here consider an experimentally realistic scenario in which transition probabilities are estimated from noisy cell population size measurements. Using aggregated data of FACS measurements, we develop MMSE and ML estimators and formulate two problems to find the minimum number of required samples and measurements to guarantee the accuracy of predicted population sizes. Our numerical results show that the convergence mechanism of transition probabilities and steady states differ widely from the real values if one uses the standard deterministic approach for noisy measurements. This provides support for our argument that for the analysis of FACS data one should consider the observed state as a random variable. The second problem we address is about the consequences of estimating the probability of a cell being in a particular state from measurements of small population of cells. We show how the uncertainty arising from small sample sizes can be captured by a distribution for the state probability.

Assessment of wadeable stream resources in the driftless area ecoregion in Western Wisconsin using a probabilistic sampling design.

PubMed

Miller, Michael A; Colby, Alison C C; Kanehl, Paul D; Blocksom, Karen

2009-03-01

The Wisconsin Department of Natural Resources (WDNR), with support from the U.S. EPA, conducted an assessment of wadeable streams in the Driftless Area ecoregion in western Wisconsin using a probabilistic sampling design. This ecoregion encompasses 20% of Wisconsin's land area and contains 8,800 miles of perennial streams. Randomly-selected stream sites (n = 60) equally distributed among stream orders 1-4 were sampled. Watershed land use, riparian and in-stream habitat, water chemistry, macroinvertebrate, and fish assemblage data were collected at each true random site and an associated "modified-random" site on each stream that was accessed via a road crossing nearest to the true random site. Targeted least-disturbed reference sites (n = 22) were also sampled to develop reference conditions for various physical, chemical, and biological measures. Cumulative distribution function plots of various measures collected at the true random sites evaluated with reference condition thresholds, indicate that high proportions of the random sites (and by inference the entire Driftless Area wadeable stream population) show some level of degradation. Study results show no statistically significant differences between the true random and modified-random sample sites for any of the nine physical habitat, 11 water chemistry, seven macroinvertebrate, or eight fish metrics analyzed. In Wisconsin's Driftless Area, 79% of wadeable stream lengths were accessible via road crossings. While further evaluation of the statistical rigor of using a modified-random sampling design is warranted, sampling randomly-selected stream sites accessed via the nearest road crossing may provide a more economical way to apply probabilistic sampling in stream monitoring programs.

A nationwide population-based study on incidence and cost of non-fatal injuries in Iran.

PubMed

Hafezi-Nejad, Nima; Rahimi-Movaghar, Afarin; Motevalian, Abbas; Amin-Esmaeili, Masoumeh; Sharifi, Vandad; Hajebi, Ahmad; Radgoodarzi, Reza; Hefazi, Mitra; Eslami, Vahid; Saadat, Soheil; Rahimi-Movaghar, Vafa

2014-10-01

Elucidating the epidemiological status of injuries is a critical component of preventive strategies in countries with high incidence of injuries, like Iran. Population-based surveys are able to estimate all types of non-fatal injuries. This study protocol is the core unit in describing Iran's national cost and epidemiology of non-fatal injuries, and also as a guide for other studies. In a cross-sectional study, 1525 primary sampling units are randomly selected with probability proportional to size regarding the number of households in each enumeration area based on Iran's 2006 national census. Six of the households are randomly selected. One member of each household is chosen using Kish Grid tables. In all, 9150 subjects are selected. Data on demographics are collected. For each injury during the past three months, activity, place, mechanism, site, type and the place of treatment are coded to match the International Classification of Diseases, 10th revision 2012 (ICD10-2012) classifications. Subjects are contacted via telephone to obtain data on cost of injury. Finally, sampling weights are calculated so that data for each respondent can be inflated to represent other individuals in Iran. Quality control and quality assurance issues are discussed. Our objectives will describe the present impact and the future priorities of injury prevention in Iran. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Kidney function changes with aging in adults: comparison between cross-sectional and longitudinal data analyses in renal function assessment.

PubMed

Chung, Sang M; Lee, David J; Hand, Austin; Young, Philip; Vaidyanathan, Jayabharathi; Sahajwalla, Chandrahas

2015-12-01

The study evaluated whether the renal function decline rate per year with age in adults varies based on two primary statistical analyses: cross-section (CS), using one observation per subject, and longitudinal (LT), using multiple observations per subject over time. A total of 16628 records (3946 subjects; age range 30-92 years) of creatinine clearance and relevant demographic data were used. On average, four samples per subject were collected for up to 2364 days (mean: 793 days). A simple linear regression and random coefficient models were selected for CS and LT analyses, respectively. The renal function decline rates per year were 1.33 and 0.95 ml/min/year for CS and LT analyses, respectively, and were slower when the repeated individual measurements were considered. The study confirms that rates are different based on statistical analyses, and that a statistically robust longitudinal model with a proper sampling design provides reliable individual as well as population estimates of the renal function decline rates per year with age in adults. In conclusion, our findings indicated that one should be cautious in interpreting the renal function decline rate with aging information because its estimation was highly dependent on the statistical analyses. From our analyses, a population longitudinal analysis (e.g. random coefficient model) is recommended if individualization is critical, such as a dose adjustment based on renal function during a chronic therapy. Copyright © 2015 John Wiley & Sons, Ltd.

Statistical modeling of interfractional tissue deformation and its application in radiation therapy planning

NASA Astrophysics Data System (ADS)

Vile, Douglas J.

In radiation therapy, interfraction organ motion introduces a level of geometric uncertainty into the planning process. Plans, which are typically based upon a single instance of anatomy, must be robust against daily anatomical variations. For this problem, a model of the magnitude, direction, and likelihood of deformation is useful. In this thesis, principal component analysis (PCA) is used to statistically model the 3D organ motion for 19 prostate cancer patients, each with 8-13 fractional computed tomography (CT) images. Deformable image registration and the resultant displacement vector fields (DVFs) are used to quantify the interfraction systematic and random motion. By applying the PCA technique to the random DVFs, principal modes of random tissue deformation were determined for each patient, and a method for sampling synthetic random DVFs was developed. The PCA model was then extended to describe the principal modes of systematic and random organ motion for the population of patients. A leave-one-out study tested both the systematic and random motion model's ability to represent PCA training set DVFs. The random and systematic DVF PCA models allowed the reconstruction of these data with absolute mean errors between 0.5-0.9 mm and 1-2 mm, respectively. To the best of the author's knowledge, this study is the first successful effort to build a fully 3D statistical PCA model of systematic tissue deformation in a population of patients. By sampling synthetic systematic and random errors, organ occupancy maps were created for bony and prostate-centroid patient setup processes. By thresholding these maps, PCA-based planning target volume (PTV) was created and tested against conventional margin recipes (van Herk for bony alignment and 5 mm fixed [3 mm posterior] margin for centroid alignment) in a virtual clinical trial for low-risk prostate cancer. Deformably accumulated delivered dose served as a surrogate for clinical outcome. For the bony landmark setup subtrial, the PCA PTV significantly (p<0.05) reduced D30, D20, and D5 to bladder and D50 to rectum, while increasing rectal D20 and D5. For the centroid-aligned setup, the PCA PTV significantly reduced all bladder DVH metrics and trended to lower rectal toxicity metrics. All PTVs covered the prostate with the prescription dose.

The association between pre-hypertension status and oxidative stress markers related to atherosclerotic disease: the ATTICA study.

PubMed

Chrysohoou, Christina; Panagiotakos, Demosthenes B; Pitsavos, Christos; Skoumas, John; Economou, Manolis; Papadimitriou, Lambros; Stefanadis, Christodoulos

2007-05-01

We sought to evaluate the association between pre-hypertension status and oxidative stress markers (total antioxidant capacity (TAC) and oxidized low density lipoprotein (LDL)), in a random sample of cardiovascular disease-free adults. The ATTICA study is a cross-sectional population-based survey that conducted in Attica region during 2001-2002. Based on a multistage and stratified random sampling, 1514 men and 1528 women (18-89 years old) were enrolled. The survey included a detailed interview; blood samples collected after 12h of fasting and, among other clinical measurements, status of blood pressure levels was evaluated. Six hundred and fifty-three men (43%) and 535 women (35%) were defined as pre-hypertensives. Both systolic and diastolic blood pressures were inversely correlated with TAC (p<0.001) and positively correlated to oxidized LDL (p<0.001). Particularly, compared to normotensive subjects, pre-hypertensives had 7% lower TAC levels (p<0.001) and 15% higher oxidized LDL levels (p<0.05), after correcting for multiple comparisons and adjusting for age, body mass index, blood lipids, glucose, food groups consumed and other potential confounders. Studying a large sample of cardiovascular disease-free adults, we revealed an association of pre-hypertension with oxidative stress markers linking to atherosclerotic process.

Random glucose is useful for individual prediction of type 2 diabetes: results of the Study of Health in Pomerania (SHIP).

PubMed

Kowall, Bernd; Rathmann, Wolfgang; Giani, Guido; Schipf, Sabine; Baumeister, Sebastian; Wallaschofski, Henri; Nauck, Matthias; Völzke, Henry

2013-04-01

Random glucose is widely used in routine clinical practice. We investigated whether this non-standardized glycemic measure is useful for individual diabetes prediction. The Study of Health in Pomerania (SHIP), a population-based cohort study in north-east Germany, included 3107 diabetes-free persons aged 31-81 years at baseline in 1997-2001. 2475 persons participated at 5-year follow-up and gave self-reports of incident diabetes. For the total sample and for subjects aged ≥50 years, statistical properties of prediction models with and without random glucose were compared. A basic model (including age, sex, diabetes of parents, hypertension and waist circumference) and a comprehensive model (additionally including various lifestyle variables and blood parameters, but not HbA1c) performed statistically significantly better after adding random glucose (e.g., the area under the receiver-operating curve (AROC) increased from 0.824 to 0.856 after adding random glucose to the comprehensive model in the total sample). Likewise, adding random glucose to prediction models which included HbA1c led to significant improvements of predictive ability (e.g., for subjects ≥50 years, AROC increased from 0.824 to 0.849 after adding random glucose to the comprehensive model+HbA1c). Random glucose is useful for individual diabetes prediction, and improves prediction models including HbA1c. Copyright © 2012 Primary Care Diabetes Europe. Published by Elsevier Ltd. All rights reserved.

Genetic algorithms with memory- and elitism-based immigrants in dynamic environments.

PubMed

Yang, Shengxiang

2008-01-01

In recent years the genetic algorithm community has shown a growing interest in studying dynamic optimization problems. Several approaches have been devised. The random immigrants and memory schemes are two major ones. The random immigrants scheme addresses dynamic environments by maintaining the population diversity while the memory scheme aims to adapt genetic algorithms quickly to new environments by reusing historical information. This paper investigates a hybrid memory and random immigrants scheme, called memory-based immigrants, and a hybrid elitism and random immigrants scheme, called elitism-based immigrants, for genetic algorithms in dynamic environments. In these schemes, the best individual from memory or the elite from the previous generation is retrieved as the base to create immigrants into the population by mutation. This way, not only can diversity be maintained but it is done more efficiently to adapt genetic algorithms to the current environment. Based on a series of systematically constructed dynamic problems, experiments are carried out to compare genetic algorithms with the memory-based and elitism-based immigrants schemes against genetic algorithms with traditional memory and random immigrants schemes and a hybrid memory and multi-population scheme. The sensitivity analysis regarding some key parameters is also carried out. Experimental results show that the memory-based and elitism-based immigrants schemes efficiently improve the performance of genetic algorithms in dynamic environments.

Application of random effects to the study of resource selection by animals

USGS Publications Warehouse

Gillies, C.S.; Hebblewhite, M.; Nielsen, S.E.; Krawchuk, M.A.; Aldridge, Cameron L.; Frair, J.L.; Saher, D.J.; Stevens, C.E.; Jerde, C.L.

2006-01-01

1. Resource selection estimated by logistic regression is used increasingly in studies to identify critical resources for animal populations and to predict species occurrence.2. Most frequently, individual animals are monitored and pooled to estimate population-level effects without regard to group or individual-level variation. Pooling assumes that both observations and their errors are independent, and resource selection is constant given individual variation in resource availability.3. Although researchers have identified ways to minimize autocorrelation, variation between individuals caused by differences in selection or available resources, including functional responses in resource selection, have not been well addressed.4. Here we review random-effects models and their application to resource selection modelling to overcome these common limitations. We present a simple case study of an analysis of resource selection by grizzly bears in the foothills of the Canadian Rocky Mountains with and without random effects.5. Both categorical and continuous variables in the grizzly bear model differed in interpretation, both in statistical significance and coefficient sign, depending on how a random effect was included. We used a simulation approach to clarify the application of random effects under three common situations for telemetry studies: (a) discrepancies in sample sizes among individuals; (b) differences among individuals in selection where availability is constant; and (c) differences in availability with and without a functional response in resource selection.6. We found that random intercepts accounted for unbalanced sample designs, and models with random intercepts and coefficients improved model fit given the variation in selection among individuals and functional responses in selection. Our empirical example and simulations demonstrate how including random effects in resource selection models can aid interpretation and address difficult assumptions limiting their generality. This approach will allow researchers to appropriately estimate marginal (population) and conditional (individual) responses, and account for complex grouping, unbalanced sample designs and autocorrelation.

Application of random effects to the study of resource selection by animals.

PubMed

Gillies, Cameron S; Hebblewhite, Mark; Nielsen, Scott E; Krawchuk, Meg A; Aldridge, Cameron L; Frair, Jacqueline L; Saher, D Joanne; Stevens, Cameron E; Jerde, Christopher L

2006-07-01

1. Resource selection estimated by logistic regression is used increasingly in studies to identify critical resources for animal populations and to predict species occurrence. 2. Most frequently, individual animals are monitored and pooled to estimate population-level effects without regard to group or individual-level variation. Pooling assumes that both observations and their errors are independent, and resource selection is constant given individual variation in resource availability. 3. Although researchers have identified ways to minimize autocorrelation, variation between individuals caused by differences in selection or available resources, including functional responses in resource selection, have not been well addressed. 4. Here we review random-effects models and their application to resource selection modelling to overcome these common limitations. We present a simple case study of an analysis of resource selection by grizzly bears in the foothills of the Canadian Rocky Mountains with and without random effects. 5. Both categorical and continuous variables in the grizzly bear model differed in interpretation, both in statistical significance and coefficient sign, depending on how a random effect was included. We used a simulation approach to clarify the application of random effects under three common situations for telemetry studies: (a) discrepancies in sample sizes among individuals; (b) differences among individuals in selection where availability is constant; and (c) differences in availability with and without a functional response in resource selection. 6. We found that random intercepts accounted for unbalanced sample designs, and models with random intercepts and coefficients improved model fit given the variation in selection among individuals and functional responses in selection. Our empirical example and simulations demonstrate how including random effects in resource selection models can aid interpretation and address difficult assumptions limiting their generality. This approach will allow researchers to appropriately estimate marginal (population) and conditional (individual) responses, and account for complex grouping, unbalanced sample designs and autocorrelation.

LEGEND, a LEO-to-GEO Environment Debris Model

NASA Technical Reports Server (NTRS)

Liou, Jer Chyi; Hall, Doyle T.

2013-01-01

LEGEND (LEO-to-GEO Environment Debris model) is a three-dimensional orbital debris evolutionary model that is capable of simulating the historical and future debris populations in the near-Earth environment. The historical component in LEGEND adopts a deterministic approach to mimic the known historical populations. Launched rocket bodies, spacecraft, and mission-related debris (rings, bolts, etc.) are added to the simulated environment. Known historical breakup events are reproduced, and fragments down to 1 mm in size are created. The LEGEND future projection component adopts a Monte Carlo approach and uses an innovative pair-wise collision probability evaluation algorithm to simulate the future breakups and the growth of the debris populations. This algorithm is based on a new "random sampling in time" approach that preserves characteristics of the traditional approach and captures the rapidly changing nature of the orbital debris environment. LEGEND is a Fortran 90-based numerical simulation program. It operates in a UNIX/Linux environment.

Risk factors for operated carpal tunnel syndrome: a multicenter population-based case-control study

PubMed Central

Mattioli, Stefano; Baldasseroni, Alberto; Bovenzi, Massimo; Curti, Stefania; Cooke, Robin MT; Campo, Giuseppe; Barbieri, Pietro G; Ghersi, Rinaldo; Broccoli, Marco; Cancellieri, Maria Pia; Colao, Anna Maria; dell'Omo, Marco; Fateh-Moghadam, Pirous; Franceschini, Flavia; Fucksia, Serenella; Galli, Paolo; Gobba, Fabriziomaria; Lucchini, Roberto; Mandes, Anna; Marras, Teresa; Sgarrella, Carla; Borghesi, Stefano; Fierro, Mauro; Zanardi, Francesca; Mancini, Gianpiero; Violante, Francesco S

2009-01-01

Background Carpal tunnel syndrome (CTS) is a socially and economically relevant disease caused by compression or entrapment of the median nerve within the carpal tunnel. This population-based case-control study aims to investigate occupational/non-occupational risk factors for surgically treated CTS. Methods Cases (n = 220) aged 18-65 years were randomly drawn from 13 administrative databases of citizens who were surgically treated with carpal tunnel release during 2001. Controls (n = 356) were randomly sampled from National Health Service registry records and were frequency matched by age-gender-specific CTS hospitalization rates. Results At multivariate analysis, risk factors were blue-collar/housewife status, BMI ≥ 30 kg/m2, sibling history of CTS and coexistence of trigger finger. Being relatively tall (cut-offs based on tertiles: women ≥165 cm; men ≥175 cm) was associated with lower risk. Blue-collar work was a moderate/strong risk factor in both sexes. Raised risks were apparent for combinations of biomechanical risk factors that included frequent repetitivity and sustained force. Conclusion This study strongly underlines the relevance of biomechanical exposures in both non-industrial and industrial work as risk factors for surgically treated CTS. PMID:19758429

[Prevalence of leisure-time physical activity and associated factors: a population-based study in São Paulo, Brazil, 2008-2009].

PubMed

Sousa, Clóvis Arlindo de; César, Chester Luiz Galvão; Barros, Marilisa Berti de Azevedo; Carandina, Luana; Goldbaum, Moisés; Marchioni, Dirce Maria Lobo; Fisberg, Regina Mara

2013-02-01

The purpose of this study was to ascertain the prevalence of self-reported leisure-time physical activity and related factors in the city of São Paulo, Brazil, 2008-2009. A population- based cross-sectional study interviewed 2,691 individuals of both sexes, 12 years or older. A two-stage cluster (census tract, household) random sample provided data using home interviews in 2008 and 2009. Leisure-time physical activity was measured with IPAQ, long version. Complex sample-adjusted descriptive statistics provided prevalence estimates, chi-square tests screened associations, and prevalence ratios (PR) expressed effects. Multiple Poisson regression was used to ascertain adjusted effects, and design effects were calculated. Of the interviewees, 16.4% (95%CI: 14.3-18.7) reported leisure-time physical activity. The findings indicate the importance of encouraging leisure-time physical activity, which was associated with male sex, higher income, younger age (12 to 29 years), not smoking, and not reporting frequent fatigue.

An occupational exposure assessment of a perfluorooctanesulfonyl fluoride production site: biomonitoring.

PubMed

Olsen, Geary W; Logan, Perry W; Hansen, Kristen J; Simpson, Cathy A; Burris, Jean M; Burlew, Michele M; Vorarath, Phanasouk P; Venkateswarlu, Pothapragada; Schumpert, John C; Mandel, Jeffrey H

2003-01-01

This investigation randomly sampled a fluorochemical manufacturing employee population to determine the distribution of serum fluorochemical levels according to employees' jobs and work areas. Previous analyses of medical surveillance data have not shown significant associations between fluorochemical production employees' clinical chemistry and hematology tests and their serum PFOS and perfluorooctanoate (PFOA, C(7)F(15)COO(-)) concentrations, but may have been subject to nonparticipation bias. A random sample of the on-site film plant employee population, where fluorochemicals are not produced, determined their serum concentrations also. Of the 232 employees randomly selected for serum sampling, 186 (80%) employees participated (n=126 chemical plant; n=60 film plant). Sera samples were extracted using an ion-pairing extraction procedure and were quantitatively analyzed for seven fluorochemicals using high-pressure liquid chromatography electrospray tandem mass spectrometry methods. Geometric means (in parts per million) and 95% confidence intervals (in parentheses) of the random sample of 126 chemical plant employees were: PFOS 0.941 (0.787-1.126); PFOA 0.899 (0.722-1.120); perfluorohexanesulfonate 0.180 (0.145-0.223); N-ethyl perfluorooctanesulfonamidoacetate 0.008 (0.006-0.011); N-methyl perfluorooctanesulfonamidoacetate 0.081 (0.067-0.098); perfluorooctanesulfonamide 0.013 (0.009-0.018); and perfluorooctanesulfonamidoacetate 0.022 (0.018-0.029). These geometric means were approximately one order of magnitude higher than those observed for the film plant employees.

Disparities in fatal and non-fatal injuries between Irish travellers and the Irish general population are similar to those of other indigenous minorities: a cross-sectional population-based comparative study

PubMed Central

Abdalla, Safa; Kelleher, Cecily C; Quirke, Brigid; Daly, Leslie

2013-01-01

Objectives To assess recent disparities in fatal and non-fatal injury between travellers and the general population in Ireland. Design A cross-sectional population-based comparative study. Setting Republic of Ireland. Participants Population census and retrospective mortality data were collected from 7042 traveller families, travellers being those identified by themselves and others as members of the traveller community. Retrospective injury incidence was estimated from a survey of a random sample of travellers in private households, aged 15 years or over (702 men and 961 women). Comparable general population data were obtained from official statistical reports, while retrospective incidence was estimated from the Survey of Lifestyle, Attitude and Nutrition 2002, a random sample of 5992 adults in private households aged 18 years or over. Outcome measures Potential Years of Life Lost (PYLL), Standardised Mortality Ratios (SMR), Standardised Incidence Ratios (SIR) and Case Fatality Ratios (CFR). Results Injury accounted for 36% of PYLL among travellers, compared with 13% in the general population. travellers were more likely to die of unintentional injury than the general population (SMR=454 (95% CI 279 to 690) in men and 460 (95% CI 177 to 905) in women), with a similar pattern for intentional injury (SMR=637 (95% CI 367 to 993) in men and 464 (95% CI 107 to 1204 in women). They had a lower incidence of unintentional injury but those aged 65 years or over were about twice as likely to report an injury. Travellers had a higher incidence of intentional injuries (SIR=181 (95% CI 116 to 269) in men and 268 (95% CI 187 to 373) in women). Injury CFR were consistently higher among travellers. Conclusions Irish travellers continue to bear a disproportionate burden of injury, which calls for scaling up injury prevention efforts in this group. Prevention and further research should focus on suicide, alcohol misuse and elderly injury among Irish travellers. PMID:23358563

Improving the Rank Precision of Population Health Measures for Small Areas with Longitudinal and Joint Outcome Models

PubMed Central

Athens, Jessica K.; Remington, Patrick L.; Gangnon, Ronald E.

2015-01-01

Objectives The University of Wisconsin Population Health Institute has published the County Health Rankings since 2010. These rankings use population-based data to highlight health outcomes and the multiple determinants of these outcomes and to encourage in-depth health assessment for all United States counties. A significant methodological limitation, however, is the uncertainty of rank estimates, particularly for small counties. To address this challenge, we explore the use of longitudinal and pooled outcome data in hierarchical Bayesian models to generate county ranks with greater precision. Methods In our models we used pooled outcome data for three measure groups: (1) Poor physical and poor mental health days; (2) percent of births with low birth weight and fair or poor health prevalence; and (3) age-specific mortality rates for nine age groups. We used the fixed and random effects components of these models to generate posterior samples of rates for each measure. We also used time-series data in longitudinal random effects models for age-specific mortality. Based on the posterior samples from these models, we estimate ranks and rank quartiles for each measure, as well as the probability of a county ranking in its assigned quartile. Rank quartile probabilities for univariate, joint outcome, and/or longitudinal models were compared to assess improvements in rank precision. Results The joint outcome model for poor physical and poor mental health days resulted in improved rank precision, as did the longitudinal model for age-specific mortality rates. Rank precision for low birth weight births and fair/poor health prevalence based on the univariate and joint outcome models were equivalent. Conclusion Incorporating longitudinal or pooled outcome data may improve rank certainty, depending on characteristics of the measures selected. For measures with different determinants, joint modeling neither improved nor degraded rank precision. This approach suggests a simple way to use existing information to improve the precision of small-area measures of population health. PMID:26098858

Reaching Asian Americans: sampling strategies and incentives.

PubMed

Lee, Soo-Kyung; Cheng, Yu-Yao

2006-07-01

Reaching and recruiting representative samples of minority populations is often challenging. This study examined in Chinese and Korean Americans: 1) whether using two different sampling strategies (random sampling vs. convenience sampling) significantly affected characteristics of recruited participants and 2) whether providing different incentives in the mail survey produced different response rates. We found statistically significant, however mostly not remarkable, differences between random and convenience samples. Offering monetary incentives in the mail survey improved response rates among Chinese Americans, while offering a small gift did not improve response rates among either Chinese or Korean Americans. This information will be useful for researchers and practitioners working with Asian Americans.

Seroprevalence after vaccination of cattle and sheep against Bluetongue Virus (BTV) serotype 8 in Sweden.

PubMed

Hultén, C; Frössling, J; Chenais, E; Sternberg Lewerin, S

2013-10-01

Sweden experienced its first outbreak of bluetongue virus (BTV) infection beginning in September 2008. Mandatory vaccination with an inactivated vaccine (BTVPUR Alsap8; Merial, Lyon, France) began 2 days after bluetongue was confirmed in the country. The aim of this study was to investigate whether the goal of 80% seroconversion by the susceptible population within the vaccination area was met during the initial phase of the Swedish vaccination campaign and whether there were discrepancies between subpopulations. Milk or blood samples were collected from 274 cattle randomly selected from the vaccinated population. Blood samples were also collected from ten ewes on each of 28 randomly selected vaccinated herds. The vaccination campaign in Sweden may be regarded as successful, as measured by apparent seroprevalence in the vaccinated population. The overall apparent seroprevalence was 77%, and in cattle, which constituted the majority of the susceptible population, the apparent seroprevalence was 82%. Factors that influenced the titres after vaccination were as follows: (i) the time span between vaccination and sampling and (ii) the age of the animals. © 2012 Blackwell Verlag GmbH.

Academic Freedom in Al Al-Bayt University and the Level of Practicing It from the View Point of the Faculty Members Based on Some Variables

ERIC Educational Resources Information Center

Al-Madi, Bayan

2013-01-01

The purpose of this study is to identify the level of practicing academic freedom by the faculty members of Al al-Bayt University. The study population included all the faculty members (297) of Al al-Bayt University, during the academic year, 2010/2011. The study sample was randomly selected and included 250 faculty members. To achieve the aims of…

Methodological Challenges in Collecting Social and Behavioural Data Regarding the HIV Epidemic among Gay and Other Men Who Have Sex with Men in Australia

PubMed Central

Holt, Martin; de Wit, John; Brown, Graham; Maycock, Bruce; Fairley, Christopher; Prestage, Garrett

2014-01-01

Background Behavioural surveillance and research among gay and other men who have sex with men (GMSM) commonly relies on non-random recruitment approaches. Methodological challenges limit their ability to accurately represent the population of adult GMSM. We compared the social and behavioural profiles of GMSM recruited via venue-based, online, and respondent-driven sampling (RDS) and discussed their utility for behavioural surveillance. Methods Data from four studies were selected to reflect each recruitment method. We compared demographic characteristics and the prevalence of key indicators including sexual and HIV testing practices obtained from samples recruited through different methods, and population estimates from respondent-driven sampling partition analysis. Results Overall, the socio-demographic profile of GMSM was similar across samples, with some differences observed in age and sexual identification. Men recruited through time-location sampling appeared more connected to the gay community, reported a greater number of sexual partners, but engaged in less unprotected anal intercourse with regular (UAIR) or casual partners (UAIC). The RDS sample overestimated the proportion of HIV-positive men and appeared to recruit men with an overall higher number of sexual partners. A single-website survey recruited a sample with characteristics which differed considerably from the population estimates with regards to age, ethnically diversity and behaviour. Data acquired through time-location sampling underestimated the rates of UAIR and UAIC, while RDS and online sampling both generated samples that underestimated UAIR. Simulated composite samples combining recruits from time-location and multi-website online sampling may produce characteristics more consistent with the population estimates, particularly with regards to sexual practices. Conclusion Respondent-driven sampling produced the sample that was most consistent to population estimates, but this methodology is complex and logistically demanding. Time-location and online recruitment are more cost-effective and easier to implement; using these approaches in combination may offer the potential to recruit a more representative sample of GMSM. PMID:25409440

Methodological challenges in collecting social and behavioural data regarding the HIV epidemic among gay and other men who have sex with men in Australia.

PubMed

Zablotska, Iryna B; Frankland, Andrew; Holt, Martin; de Wit, John; Brown, Graham; Maycock, Bruce; Fairley, Christopher; Prestage, Garrett

2014-01-01

Behavioural surveillance and research among gay and other men who have sex with men (GMSM) commonly relies on non-random recruitment approaches. Methodological challenges limit their ability to accurately represent the population of adult GMSM. We compared the social and behavioural profiles of GMSM recruited via venue-based, online, and respondent-driven sampling (RDS) and discussed their utility for behavioural surveillance. Data from four studies were selected to reflect each recruitment method. We compared demographic characteristics and the prevalence of key indicators including sexual and HIV testing practices obtained from samples recruited through different methods, and population estimates from respondent-driven sampling partition analysis. Overall, the socio-demographic profile of GMSM was similar across samples, with some differences observed in age and sexual identification. Men recruited through time-location sampling appeared more connected to the gay community, reported a greater number of sexual partners, but engaged in less unprotected anal intercourse with regular (UAIR) or casual partners (UAIC). The RDS sample overestimated the proportion of HIV-positive men and appeared to recruit men with an overall higher number of sexual partners. A single-website survey recruited a sample with characteristics which differed considerably from the population estimates with regards to age, ethnically diversity and behaviour. Data acquired through time-location sampling underestimated the rates of UAIR and UAIC, while RDS and online sampling both generated samples that underestimated UAIR. Simulated composite samples combining recruits from time-location and multi-website online sampling may produce characteristics more consistent with the population estimates, particularly with regards to sexual practices. Respondent-driven sampling produced the sample that was most consistent to population estimates, but this methodology is complex and logistically demanding. Time-location and online recruitment are more cost-effective and easier to implement; using these approaches in combination may offer the potential to recruit a more representative sample of GMSM.

The Use and the Prescription Pattern of Traditional Chinese Medicine Among Urolithiasis Patients in Taiwan: A Population-Based Study.

PubMed

Lin, Po-Hung; Lin, Shun-Ku; Hsu, Ren-Jun; Cheng, Kuan-Chen; Liu, Jui-Ming

2016-01-01

To investigate the pattern of Traditional Chinese Medicine (TCM) usage for urolithiasis patients in Taiwan and to determine the most common Chinese herbal products used for urolithiasis. Retrospective review of urolithiasis patients treated with TCM treatment. One million randomly selected samples in the Taiwanese National Health Insurance Research Database between 1997 and 2008. Eighty-two thousand five hundred and fifty-one newly diagnosed urolithiasis patients. The correlation between TCM treatment, demographic factors, or medical conditions. A total of 62.6% of urolithiasis patients use TCM treatment. A younger age, female gender, polypharmacy, multiple comorbidities, and stone in the lower urinary tract result in a greater tendency to use TCM, after adjusting for demographic factors. Jia-Wei-Xiao-Yao-San Extract Powder and Ji-Sheng-Shen-Qi-Wan Extract Powder are the most frequently prescribed Chinese medicine formulae. This is the first study to examine the use of and the prescription pattern for TCM in urolithiasis patients using a random, national population-based sample. More than 62% of urolithiasis patients use TCM, and patients with polypharmacy, multiple comorbidities, and stone in the ureter are more likely to use TCM. The most frequently prescribed Chinese medicine formulae were Jia-Wei-Xiao-Yao-San Extract Powder and Ji-Sheng-Shen-Qi-Wan Extract Powder, which were reported to retard the progression of renal failure and alleviate flank pain or tenderness.

Advantage of population pharmacokinetic method for evaluating the bioequivalence and accuracy of parameter estimation of pidotimod.

PubMed

Huang, Jihan; Li, Mengying; Lv, Yinghua; Yang, Juan; Xu, Ling; Wang, Jingjing; Chen, Junchao; Wang, Kun; He, Yingchun; Zheng, Qingshan

2016-09-01

This study was aimed at exploring the accuracy of population pharmacokinetic method in evaluating the bioequivalence of pidotimod with sparse data profiles and whether this method is suitable for bioequivalence evaluation in special populations such as children with fewer samplings. Methods In this single-dose, two-period crossover study, 20 healthy male Chinese volunteers were randomized 1 : 1 to receive either the test or reference formulation, with a 1-week washout before receiving the alternative formulation. Noncompartmental and population compartmental pharmacokinetic analyses were conducted. Simulated data were analyzed to graphically evaluate the model and the pharmacokinetic characteristics of the two pidotimod formulations. Various sparse sampling scenarios were generated from the real bioequivalence clinical trial data and evaluated by population pharmacokinetic method. The 90% confidence intervals (CIs) for AUC0-12h, AUC0-∞, and Cmax were 97.3 - 118.7%, 96.9 - 118.7%, and 95.1 - 109.8%, respectively, within the 80 - 125% range for bioequivalence using noncompartmental analysis. The population compartmental pharmacokinetics of pidotimod were described using a one-compartment model with first-order absorption and lag time. In the comparison of estimations in different dataset, the estimation of random three- and< fixed four-point sampling strategies can provide results similar to those obtained through rich sampling. The nonlinear mixed-effects model requires fewer data points. Moreover, compared with the noncompartmental analysis method, the pharmacokinetic parameters can be more accurately estimated using nonlinear mixed-effects model. The population pharmacokinetic modeling method was used to assess the bioequivalence of two pidotimod formulations with relatively few sampling points and further validated the bioequivalence of the two formulations. This method may provide useful information for regulating bioequivalence evaluation in special populations.

Stalking and health – an Austrian prevalence study.

PubMed

Freidl, W; Neuberger, I; Schönberger, S; Raml, R

2011-04-01

The aim of this study was to estimate the prevalence of stalking and related subjective health impairment, based on concrete definitions of stalking, for a representative random sample of the female population in the Austrian Federal State of Styria. A representative random sample (randomised last digits procedure) of 2000 women selected from the female population of Styria aged 18 years or older underwent a computer-aided phone interview survey (CATI). Questions centred on the occurrence of stalking, the exact period of stalking, the gender of the stalker, the subjective impairment through stalking, addressing the aspects of life-style and the subjectively perceived state of health, and socio-demographic variables. For data analyses descriptive statistics, and chi(2)-tests and t-tests were applied. Lifetime prevalence varies between ca. 6% and 18%, depending on definition levels. The annual prevalences reveal a range of 1-4%. 39-43% of the stalked women feel they are impaired in their life-style, and 32-40% feel impaired in their health. Higher age and living in a partnership reduce the likelihood of being stalked. 81% of the stalked women are stalked by a male person. The prevalences found in this study are in line with other international studies, although, in a direct comparison, they are in the lower range. However, these data document the relevance of the phenomenon of stalking for the female Austrian population. © Georg Thieme Verlag KG Stuttgart · New York.

Psychiatric disorders among the Mapuche in Chile.

PubMed

Vicente, Benjamin; Kohn, Robert; Rioseco, Pedro; Saldivia, Sandra; Torres, Silverio

2005-06-01

The Mapuche are the largest indigenous group in Chile; yet almost all data on the mental health of indigenous populations are from North America. The study examines the differential DSM-III-R prevalence rates of psychiatric disorders and service utilization among indigenous and non-indigenous community residence. The Composite International Diagnostic Interview (CIDI) was administered to a stratified random sample of 75 Mapuche and 434 non-Mapuche residents of the province of Cautín. Lifetime prevalence and 12-month prevalence rates were estimated. Approximately 28.4% of the Mapuche population had a lifetime, and 15.7% a 12-month, prevalent psychiatric disorder compared to 38.0% and 25.7%, respectively, of the non-Mapuche. Few significant differences were noted between the two groups; however, generalized anxiety disorder, simple phobia, and drug dependence were less prevalent among the Mapuche. Service utilization among the Mapuche with mental illness was low. This is a preliminary study based on a small sample size. Further research on the mental health of indigenous populations of South America is needed.

Creating targeted initial populations for genetic product searches in heterogeneous markets

NASA Astrophysics Data System (ADS)

Foster, Garrett; Turner, Callaway; Ferguson, Scott; Donndelinger, Joseph

2014-12-01

Genetic searches often use randomly generated initial populations to maximize diversity and enable a thorough sampling of the design space. While many of these initial configurations perform poorly, the trade-off between population diversity and solution quality is typically acceptable for small-scale problems. Navigating complex design spaces, however, often requires computationally intelligent approaches that improve solution quality. This article draws on research advances in market-based product design and heuristic optimization to strategically construct 'targeted' initial populations. Targeted initial designs are created using respondent-level part-worths estimated from discrete choice models. These designs are then integrated into a traditional genetic search. Two case study problems of differing complexity are presented to illustrate the benefits of this approach. In both problems, targeted populations lead to computational savings and product configurations with improved market share of preferences. Future research efforts to tailor this approach and extend it towards multiple objectives are also discussed.

Estimation of population mean under systematic sampling

NASA Astrophysics Data System (ADS)

Noor-ul-amin, Muhammad; Javaid, Amjad

2017-11-01

In this study we propose a generalized ratio estimator under non-response for systematic random sampling. We also generate a class of estimators through special cases of generalized estimator using different combinations of coefficients of correlation, kurtosis and variation. The mean square errors and mathematical conditions are also derived to prove the efficiency of proposed estimators. Numerical illustration is included using three populations to support the results.

Extending cluster lot quality assurance sampling designs for surveillance programs.

PubMed

Hund, Lauren; Pagano, Marcello

2014-07-20

Lot quality assurance sampling (LQAS) has a long history of applications in industrial quality control. LQAS is frequently used for rapid surveillance in global health settings, with areas classified as poor or acceptable performance on the basis of the binary classification of an indicator. Historically, LQAS surveys have relied on simple random samples from the population; however, implementing two-stage cluster designs for surveillance sampling is often more cost-effective than simple random sampling. By applying survey sampling results to the binary classification procedure, we develop a simple and flexible nonparametric procedure to incorporate clustering effects into the LQAS sample design to appropriately inflate the sample size, accommodating finite numbers of clusters in the population when relevant. We use this framework to then discuss principled selection of survey design parameters in longitudinal surveillance programs. We apply this framework to design surveys to detect rises in malnutrition prevalence in nutrition surveillance programs in Kenya and South Sudan, accounting for clustering within villages. By combining historical information with data from previous surveys, we design surveys to detect spikes in the childhood malnutrition rate. Copyright © 2014 John Wiley & Sons, Ltd.

Internet-based guided self-help for glioma patients with depressive symptoms: design of a randomized controlled trial

PubMed Central

2014-01-01

Background Among glioma patients, depression is estimated to be more prevalent than in both the general population and the cancer patient population. This can have negative consequences for both patients and their primary informal caregivers (e.g., a spouse, family member or close friend). At present, there is no evidence from randomized controlled trials for the effectiveness of psychological treatment for depression in glioma patients. Furthermore, the possibility of delivering mental health care through the internet has not yet been explored in this population. Therefore, a randomized controlled trial is warranted to evaluate the effects of an internet-based, guided self-help intervention for depressive symptoms in glioma patients. Methods/design The intervention is based on problem-solving therapy. An existing 5-week course is adapted for use by adult glioma patients with mild to moderate depressive symptoms (Center for Epidemiology Studies Depression Scale score ≥12). Sample size calculations yield 126 glioma patients to be included, who are randomly assigned to either the intervention group or a waiting list control group. In addition, we aim to include 63 patients with haematological cancer in a non-central nervous system malignancy control group. Assessments take place at baseline, after 6 and 12 weeks, and after 6 and 12 months. Primary outcome measure is the change in depressive symptoms. Secondary outcome measures include health-related quality of life, fatigue, costs and patient satisfaction. In addition, all patients are asked to assign a primary informal caregiver, who does not participate in the intervention but who is asked to complete similar assessments. Their mood, health-related quality of life and fatigue is evaluated as well. Discussion This is the first study to evaluate the effects of problem-solving therapy delivered through the internet as treatment for depressive symptoms in glioma patients. If proven effective, this treatment will contribute to the mental health care of glioma patients in clinical practice. Trial registration Netherlands Trial Register NTR3223 PMID:24721108

Sampling through time and phylodynamic inference with coalescent and birth–death models

PubMed Central

Volz, Erik M.; Frost, Simon D. W.

2014-01-01

Many population genetic models have been developed for the purpose of inferring population size and growth rates from random samples of genetic data. We examine two popular approaches to this problem, the coalescent and the birth–death-sampling model (BDM), in the context of estimating population size and birth rates in a population growing exponentially according to the birth–death branching process. For sequences sampled at a single time, we found the coalescent and the BDM gave virtually indistinguishable results in terms of the growth rates and fraction of the population sampled, even when sampling from a small population. For sequences sampled at multiple time points, we find that the birth–death model estimators are subject to large bias if the sampling process is misspecified. Since BDMs incorporate a model of the sampling process, we show how much of the statistical power of BDMs arises from the sequence of sample times and not from the genealogical tree. This motivates the development of a new coalescent estimator, which is augmented with a model of the known sampling process and is potentially more precise than the coalescent that does not use sample time information. PMID:25401173

Seroepidemiology of HBV infection in South-East of iran; a population based study.

PubMed

Salehi, M; Alavian, S M; Tabatabaei, S V; Izadi, Sh; Sanei Moghaddam, E; Amini Kafi-Abad, S; Gharehbaghian, A; Khosravi, S; Abolghasemi, H

2012-05-01

Hepatitis B virus (HBV) infection is a major risk factor of cirrhosis and hepatocellular carcinoma affecting billions of people globally. Since information on its prevalence in general population is mandatory for formulating effective policies, this population based serological survey was conducted in Sistan and Baluchistan, where no previous epidemiological data were available. Using random cluster sampling 3989 healthy subjects were selected from 9 districts of Sistan and Baluchistan Province in southeastern Iran. The subjects' age ranged from 6 to 65 years old. Serum samples were tested for HBcAb, HBsAg. Screening tests were carried out by the third generation of ELISA. Various risk factors were recorded and multivariate analysis was performed. The prevalence of HBsAg and HBcAb in Sistan and Baluchistan was 3.38% (95% CI 2.85; 3.98) and 23.58% (95% CI 22.29; 24.93) respectively. We found 8 cases of positive anti-HDV antibody. Predictors of HBsAg or HBcAb in multivariate analysis were age, marital status and addiction. The rate of HBV infection in Sistan and Baluchistan was higher than other parts of Iran. Approximately 25% of general population in this province had previous exposure to HBV and 3% were HBsAg carriers. Intrafamilial and addiction were major routes of HBV transmission in this province.

Characteristics of a random sample of emergency food program users in New York: II. Soup kitchens.

PubMed Central

Bowering, J; Clancy, K L; Poppendieck, J

1991-01-01

A random sample of soup kitchen clients in New York City was studied and specific comparisons made on various parameters including homelessness. Compared with the general population of low income persons, soup kitchen users were overwhelmingly male, disproportionately African-American, and more likely to live alone. The homeless (41 percent of the sample) were less likely to receive food stamps or free food, or to use food pantries. Fewer of them received Medicaid or had health insurance. Forty-seven percent had no income in contrast to 29 percent of the total sample. PMID:2053673

The health of Canada's Aboriginal children: results from the First Nations and Inuit Regional Health Survey.

PubMed

MacMillan, Harriet L; Jamieson, Ellen; Walsh, Christine; Boyle, Michael; Crawford, Allison; MacMillan, Angus

2010-04-01

Reports on child health in Canada often refer to the disproportionate burden of poor health experienced by Aboriginal children and youth, yet little national data are available. This paper describes the health of First Nations and Inuit children and youth based on the First Nations and Inuit Regional Health Survey (FNIRHS). The FNIRHS combines data from 9 regional surveys conducted in 1996-1997 in Aboriginal reserve communities in all provinces. The target population consisted of all on-reserve communities. All households or a random sample of households or adults (depending on province) were selected based on their population representation. One child was randomly selected from each participating household, except in Ontario and Nova Scotia, where children were randomly selected based upon their population representation. Alberta did not include the section on children's health in their regional survey. Approximately 84% of adults, who were proxy respondents for their child, rated their children's health as very good or excellent. The most frequently reported conditions were ear problems (15%), followed by allergies (13%) and asthma (12%). Broken bones or fractures were the most frequently reported injuries (13%). Respondents reported that 17% of children had behavioural or emotional problems. Overall, 76% of children were reported to get along with the family "very well" or "quite well." While most respondents rated their child's health as very good or excellent, injuries, emotional and behavioural problems, respiratory conditions and ear problems were reported among many Aboriginal children. Issues such as substance abuse, exposure to violence and academic performance were not addressed in the 10 core survey questions. Clearly there is a need for more in-depth information about both the physical and emotional health of Aboriginal children and youth.

Prevalence of alcohol-impaired drivers based on random breath tests in a roadside survey in Catalonia (Spain).

PubMed

Alcañiz, Manuela; Guillén, Montserrat; Santolino, Miguel; Sánchez-Moscona, Daniel; Llatje, Oscar; Ramon, Lluís

2014-04-01

Sobriety checkpoints are not usually randomly located by traffic authorities. As such, information provided by non-random alcohol tests cannot be used to infer the characteristics of the general driving population. In this paper a case study is presented in which the prevalence of alcohol-impaired driving is estimated for the general population of drivers. A stratified probabilistic sample was designed to represent vehicles circulating in non-urban areas of Catalonia (Spain), a region characterized by its complex transportation network and dense traffic around the metropolis of Barcelona. Random breath alcohol concentration tests were performed during spring 2012 on 7596 drivers. The estimated prevalence of alcohol-impaired drivers was 1.29%, which is roughly a third of the rate obtained in non-random tests. Higher rates were found on weekends (1.90% on Saturdays and 4.29% on Sundays) and especially at night. The rate is higher for men (1.45%) than for women (0.64%) and it shows an increasing pattern with age. In vehicles with two occupants, the proportion of alcohol-impaired drivers is estimated at 2.62%, but when the driver was alone the rate drops to 0.84%, which might reflect the socialization of drinking habits. The results are compared with outcomes in previous surveys, showing a decreasing trend in the prevalence of alcohol-impaired drivers over time. Copyright © 2014 Elsevier Ltd. All rights reserved.

Associations between behavioural risk factors and overweight and obesity among adults in population-based samples from 31 countries.

PubMed

Pengpid, Supa; Peltzer, Karl

Concern about overweight and obesity is growing worldwide, and more research to examine behaviours associated with the risk for increased weight in adult populations is needed. The aim of this study was to estimate associations between behavioural risk factors and overweight and obesity among adults in nationally representative population samples from 20 countries in Europe, 8 countries in Asia, Australia, Chile and USA. This secondary analysis is based on the International Social Survey Program (ISSP), 2011-2013, Health and Health Care Module. In a cross-sectional population-based survey (N=48,741) (mean age 46.6 years, SD=17.4, age range 15-102 years) simple or multi-stage stratified random sampling was used, yielding representative samples of the adult population of respective countries. Body Mass Index was assessed by self-reported height and weight. Correlates were risk behaviours for chronic disease (smoking status, alcohol intake, consumption of fruits and vegetable (=FV), and physical activity). Overall, for all 31 countries the prevalence of overweight or obesity was 44.1%, 31.7% overweight and 12.4% obese. In adjusted logistic regression models, among men and among women ex-smoking was positively associated with both overweight and obesity, while light or moderate smoking overall and among men were inversely related with obesity. Moderate alcohol use was positively associated with both overweight and obesity, while heavy alcohol use was negatively associated with overweight. The daily consumption of FV was found to be protective from both overweight and obesity, overall and for men but not for women. Physical activity was positively associated with overweight but not obesity. Some risk behaviours for chronic disease appear to be associated with overweight and obesity among adults. Interventions targeting these risk behaviours may have the potential to reduce weight. Copyright © 2016 Asia Oceania Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.

Flexible sampling large-scale social networks by self-adjustable random walk

NASA Astrophysics Data System (ADS)

Xu, Xiao-Ke; Zhu, Jonathan J. H.

2016-12-01

Online social networks (OSNs) have become an increasingly attractive gold mine for academic and commercial researchers. However, research on OSNs faces a number of difficult challenges. One bottleneck lies in the massive quantity and often unavailability of OSN population data. Sampling perhaps becomes the only feasible solution to the problems. How to draw samples that can represent the underlying OSNs has remained a formidable task because of a number of conceptual and methodological reasons. Especially, most of the empirically-driven studies on network sampling are confined to simulated data or sub-graph data, which are fundamentally different from real and complete-graph OSNs. In the current study, we propose a flexible sampling method, called Self-Adjustable Random Walk (SARW), and test it against with the population data of a real large-scale OSN. We evaluate the strengths of the sampling method in comparison with four prevailing methods, including uniform, breadth-first search (BFS), random walk (RW), and revised RW (i.e., MHRW) sampling. We try to mix both induced-edge and external-edge information of sampled nodes together in the same sampling process. Our results show that the SARW sampling method has been able to generate unbiased samples of OSNs with maximal precision and minimal cost. The study is helpful for the practice of OSN research by providing a highly needed sampling tools, for the methodological development of large-scale network sampling by comparative evaluations of existing sampling methods, and for the theoretical understanding of human networks by highlighting discrepancies and contradictions between existing knowledge/assumptions of large-scale real OSN data.

Differential expression analysis for RNAseq using Poisson mixed models.

PubMed

Sun, Shiquan; Hood, Michelle; Scott, Laura; Peng, Qinke; Mukherjee, Sayan; Tung, Jenny; Zhou, Xiang

2017-06-20

Identifying differentially expressed (DE) genes from RNA sequencing (RNAseq) studies is among the most common analyses in genomics. However, RNAseq DE analysis presents several statistical and computational challenges, including over-dispersed read counts and, in some settings, sample non-independence. Previous count-based methods rely on simple hierarchical Poisson models (e.g. negative binomial) to model independent over-dispersion, but do not account for sample non-independence due to relatedness, population structure and/or hidden confounders. Here, we present a Poisson mixed model with two random effects terms that account for both independent over-dispersion and sample non-independence. We also develop a scalable sampling-based inference algorithm using a latent variable representation of the Poisson distribution. With simulations, we show that our method properly controls for type I error and is generally more powerful than other widely used approaches, except in small samples (n <15) with other unfavorable properties (e.g. small effect sizes). We also apply our method to three real datasets that contain related individuals, population stratification or hidden confounders. Our results show that our method increases power in all three data compared to other approaches, though the power gain is smallest in the smallest sample (n = 6). Our method is implemented in MACAU, freely available at www.xzlab.org/software.html. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

[Effect of data missing on population based viral load survey in HIV infected men who have sex with men sampled in 16 large cities, China].

PubMed

Jiang, Z; Dou, Z; Yan, Z H; Song, W L; Chen, Y; Ren, X L; Chen, J; Cao, W; Xu, J; Wu, Z Y

2017-09-10

Objective: To analyze the effect of missing data in population based viral load (PVL) survey in HIV infected men who have sex with men (MSM) sampled in 16 cities in China. Methods: The database of 3 virus load sampling survey conducted consecutively in HIV infected MSM population in 16 large cities (Beijing, Shanghai, Nanjing, Hangzhou, Wuhan, Chongqing, Kunming, Xi'an, Guangzhou, Shenzhen, Nanning, Urumuqi, Harbin, Changchun, Chengdu and Tianjin) during 2013-2015 was used. SPSS 17.0 software was used to describe distribution of the missing data and analyze associated factors. Results: A total of 12 150 HIV infected MSM were randomly selected for the surveys, in whom, 9 141 (75.2 % ) received virus load tests, while 3 009 (24.8 % ) received no virus load tests, whose virus load data missed. The virus load data missing rates in MSM with or without access to antiretroviral therapy (ART) were 11.5 % (765/6 675) and 39.4 % (2 060/5 223) respectively, and the virus load data missing rates were 21.9 % (1 866/8 523) and 28.4 % (959/3 374), respectively, in local residents and non-local residents (migrants). Conclusions: The analysis indicated that the data missing occurred in the virus load survey in HIV infected MSM population. ART status and census registering status were the main influencing factors. Data missing could influence the accurate evaluation of community viral load (CVL) and population viral load(PVL) levels in HIV infected MSM in China.

Invited review: study design considerations for clinical research in veterinary radiology and radiation oncology.

PubMed

Scrivani, Peter V; Erb, Hollis N

2013-01-01

High quality clinical research is essential for advancing knowledge in the areas of veterinary radiology and radiation oncology. Types of clinical research studies may include experimental studies, method-comparison studies, and patient-based studies. Experimental studies explore issues relative to pathophysiology, patient safety, and treatment efficacy. Method-comparison studies evaluate agreement between techniques or between observers. Patient-based studies investigate naturally acquired disease and focus on questions asked in clinical practice that relate to individuals or populations (e.g., risk, accuracy, or prognosis). Careful preplanning and study design are essential in order to achieve valid results. A key point to planning studies is ensuring that the design is tailored to the study objectives. Good design includes a comprehensive literature review, asking suitable questions, selecting the proper sample population, collecting the appropriate data, performing the correct statistical analyses, and drawing conclusions supported by the available evidence. Most study designs are classified by whether they are experimental or observational, longitudinal or cross-sectional, and prospective or retrospective. Additional features (e.g., controlled, randomized, or blinded) may be described that address bias. Two related challenging aspects of study design are defining an important research question and selecting an appropriate sample population. The sample population should represent the target population as much as possible. Furthermore, when comparing groups, it is important that the groups are as alike to each other as possible except for the variables of interest. Medical images are well suited for clinical research because imaging signs are categorical or numerical variables that might be predictors or outcomes of diseases or treatments. © 2013 Veterinary Radiology & Ultrasound.

Developing Sampling Frame for Case Study: Challenges and Conditions

ERIC Educational Resources Information Center

Ishak, Noriah Mohd; Abu Bakar, Abu Yazid

2014-01-01

Due to statistical analysis, the issue of random sampling is pertinent to any quantitative study. Unlike quantitative study, the elimination of inferential statistical analysis, allows qualitative researchers to be more creative in dealing with sampling issue. Since results from qualitative study cannot be generalized to the bigger population,…

Measures and models for angular correlation and angular-linear correlation. [correlation of random variables

NASA Technical Reports Server (NTRS)

Johnson, R. A.; Wehrly, T.

1976-01-01

Population models for dependence between two angular measurements and for dependence between an angular and a linear observation are proposed. The method of canonical correlations first leads to new population and sample measures of dependence in this latter situation. An example relating wind direction to the level of a pollutant is given. Next, applied to pairs of angular measurements, the method yields previously proposed sample measures in some special cases and a new sample measure in general.

Health Status of Individuals With Serious Mental Illness

PubMed Central

Dickerson, Faith B.; Brown, Clayton H.; Daumit, Gail L.; LiJuan, Fang; Goldberg, Richard W.; Wohlheiter, Karen; Dixon, Lisa B.

2006-01-01

We examined indices of the health of persons with serious mental illness. A sample of 100 adults with schizophrenia and 100 with major mood disorder were recruited from randomly selected outpatients who were receiving community-based psychiatric treatment. Participants were surveyed about health indicators using items from the National Health and Nutrition Examination Study III and the National Health Interview Survey. Their responses were compared with those of matched samples from the general population surveys. A total of 1% of persons with serious mental illness, compared with 10% from the general population sample, met criteria for all 5 of selected health indicators: nonsmoker, exercise that meets recommended standards, good dentition, absence of obesity, and absence of serious medical co-occurring illness. Within the mentally ill group, educational level, but not a diagnosis of schizophrenia versus mood disorder, was independently associated with a composite measure of health behaviors. We conclude that an examination of multiple health indicators may be used to measure overall health status in persons with serious mental illness. PMID:16469943

Prevalence of Posttraumatic Stress Disorder in Prisoners.

PubMed

Baranyi, Gergõ; Cassidy, Megan; Fazel, Seena; Priebe, Stefan; Mundt, Adrian P

2018-06-01

People involved with criminal justice frequently are exposed to violence and traumatic experiences. This may lead to posttraumatic stress disorder (PTSD); however, no review, to our knowledge, has synthetized findings in this setting. We conducted a systematic review and meta-analysis to estimate prevalence rates of PTSD in prison populations. Original studies in which prevalence rates of PTSD in unselected samples of incarcerated people were reported were systematically searched between 1980 and June 2017. Data were pooled using random-effects meta-analysis, and sources of heterogeneity for prespecified characteristics were assessed by meta-regression. We identified 56 samples comprising 21,099 imprisoned men and women from 20 countries. Point prevalence of PTSD ranged from 0.1% to 27% for male, and from 12% to 38% for female prisoner populations. The random-effects pooled point prevalence was 6.2% (95% confidence interval: 3.9, 9.0) in male prisoners and 21.1% (95% confidence interval: 16.9, 25.6) in female prisoners. The heterogeneity between the included studies was very high. Higher prevalence was reported in samples of female prisoners, smaller studies (n < 100), and for investigations based in high-income countries. Existing evidence shows high levels of PTSD among imprisoned people, especially women. Psychosocial interventions to prevent violence, especially against children and women, and to mitigate its consequences in marginalized communities must be improved. Trauma-informed approaches for correctional programs and scalable PTSD treatments in prisons require further consideration.

Prevalence of sexually transmitted infections and bacterial vaginosis among women in sub-Saharan Africa: An individual participant data meta-analysis of 18 HIV prevention studies

PubMed Central

Morrison, Charles S.; Chen, Pai-Lien; Kwok, Cynthia; McCormack, Sheena; McGrath, Nuala; Watson-Jones, Deborah; Gottlieb, Sami L.

2018-01-01

Background Estimates of sexually transmitted infection (STI) prevalence are essential for efforts to prevent and control STIs. Few large STI prevalence studies exist, especially for low- and middle-income countries (LMICs). Our primary objective was to estimate the prevalence of chlamydia, gonorrhea, trichomoniasis, syphilis, herpes simplex virus type 2 (HSV-2), and bacterial vaginosis (BV) among women in sub-Saharan Africa by age, region, and population type. Methods and findings We analyzed individual-level data from 18 HIV prevention studies (cohort studies and randomized controlled trials; conducted during 1993–2011), representing >37,000 women, that tested participants for ≥1 selected STIs or BV at baseline. We used a 2-stage meta-analysis to combine data. After calculating the proportion of participants with each infection and standard error by study, we used a random-effects model to obtain a summary mean prevalence of each infection and 95% confidence interval (CI) across ages, regions, and population types. Despite substantial study heterogeneity for some STIs/populations, several patterns emerged. Across the three primary region/population groups (South Africa community-based, Southern/Eastern Africa community-based, and Eastern Africa higher-risk), prevalence was higher among 15–24-year-old than 25–49-year-old women for all STIs except HSV-2. In general, higher-risk populations had greater prevalence of gonorrhea and syphilis than clinic/community-based populations. For chlamydia, prevalence among 15–24-year-olds was 10.3% (95% CI: 7.4%, 14.1%; I2 = 75.7%) among women specifically recruited from higher-risk settings for HIV in Eastern Africa and was 15.1% (95% CI: 12.7%, 17.8%; I2 = 82.3%) in South African clinic/community-based populations. Among clinic/community-based populations, prevalence was generally greater in South Africa than in Southern/Eastern Africa for most STIs; for gonorrhea, prevalence among 15–24-year-olds was 4.6% (95% CI: 3.3%, 6.4%; I2 = 82.8%) in South Africa and was 1.7% (95% CI: 1.2%, 2.6%; I2 = 55.2%) in Southern/Eastern Africa. Across the three primary region/population groups, HSV-2 and BV prevalence was high among 25–49-year-olds (ranging from 70% to 83% and 33% to 44%, respectively). The main study limitation is that the data are not from random samples of the target populations. Conclusions Combining data from 18 HIV prevention studies, our findings highlight important features of STI/BV epidemiology among sub-Saharan African women. This methodology can be used where routine STI surveillance is limited and offers a new approach to obtaining critical information on STI and BV prevalence in LMICs. PMID:29485986

Evaluation of nitrite contamination in baby foods and infant formulas marketed in Turkey.

PubMed

Erkekoglu, Pinar; Baydar, Terken

2009-05-01

Nitrites are responsible for methemoglobinemia, to which infants younger than 6 months are thought to be the most susceptible population. This study aimed to detect whether there was any nitrite contamination in infant formulas and baby foods marketed in Turkey and to estimate possible toxicological risks in this sensitive physiological period. For this purpose, the samples were randomly collected and divided into four groups: milk-based, cereal-based, vegetable-based, and fruit-based. An easy and reliable spectrophotometric method was used by modifying the Griess method. The average nitrite contamination was found to be 204.07+/-65.80 microg/g in 42 samples, with 1,073 microg/g maximum. According to the results, baby and infant formulas include various nitrite levels; nitrite contamination might come from several sources during manufacturing, and so extreme attention must be given throughout the manufacturing process of food for infants.

Prevalence of Mycoplasma genitalium in different population groups: systematic review andmeta-analysis.

PubMed

Baumann, Lukas; Cina, Manuel; Egli-Gany, Dianne; Goutaki, Myrofora; Halbeisen, Florian S; Lohrer, Gian-Reto; Ali, Hammad; Scott, Pippa; Low, Nicola

2018-06-01

Mycoplasma genitalium is a common cause of non-gonococcal non-chlamydial urethritis and cervicitis. Testing of asymptomatic populations has been proposed, but prevalence in asymptomatic populations is not well established. We aimed to estimate the prevalence of M. genitalium in the general population, pregnant women, men who have sex with men (MSM), commercial sex workers (CSWs) and clinic-based samples, METHODS: We searched Embase, Medline, IndMED, African Index Medicus and LILACS from 1 January 1991 to 12 July 2016 without language restrictions. We included studies with 500 participants or more. Two reviewers independently screened and selected studies and extracted data. We examined forest plots and conducted random-effects meta-analysis to estimate prevalence, if appropriate. Between-study heterogeneity was examined using the I 2 statistic and meta-regression. Of 3316 screened records, 63 were included. In randomly selected samples from the general population, the summary prevalence was 1.3% (95% CI 1.0% to 1.8%, I 2 41.5%, three studies, 9091 people) in countries with higher levels of development and 3.9% (95% CI 2.2 to 6.7, I 2 89.2%, three studies, 3809 people) in countries with lower levels. Prevalence was similar in women and men (P=0.47). In clinic based samples, prevalence estimates were higher, except in asymptomatic patients (0.8%, 95% CI 0.4 to 1.4, I 2 0.0%, three studies, 2889 people). Summary prevalence estimates were, in the following groups: pregnant women 0.9% (95% CI 0.6% to 1.4%, I 2 0%, four studies, 3472 people), MSM in the community 3.2% (95% CI 2.1 to 5.1, I 2 78.3%, five studies, 3012 people) and female CSWs in the community 15.9% (95% CI 13.5 to 18.9, I 2 79.9%, four studies, 4006 people). This systematic review can inform testing guidelines for M. genitalium . The low estimated prevalence of M. genitalium in the general population, pregnant women and asymptomatic attenders at clinics does not support expansion of testing to these groups. PROSPERO: CRD42015020420. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Outcomes of a Behavioral Intervention to Reduce HIV Risk among Drug-involved Female Sex Workers

PubMed Central

Surratt, Hilary L.; O’Grady, Catherine; Kurtz, Steven P.; Levi-Minzi, Maria A.; Chen, Minxing

2014-01-01

Although street-based female sex workers (FSWs) are highly vulnerable to HIV, they often lack access to needed health services and medical care. This paper reports the results of a recently completed randomized intervention trial for FSWs in Miami, Florida, which tested the relative efficacy of two case management interventions that aimed to link underserved FSWs with health services and to reduce risk behaviors for HIV. Participants were recruited using targeted sampling strategies and were randomly assigned to: a Strengths-Based/Professional Only (PO) or a Strengths-Based/Professional-Peer condition (PP). Follow-up data were collected 3 and 6 months post-baseline. Outcome analyses indicated that both intervention groups displayed significant reductions in HIV risk behaviors and significant increases in services utilization; the Professional-Peer condition provided no added benefit. HIV seropositive FSWs responded particularly well to the interventions, suggesting the utility of brief strengths-based case management interventions for this population in future initiatives. PMID:24558098

Estimation of divergence from Hardy-Weinberg form.

PubMed

Stark, Alan E

2015-08-01

The Hardy–Weinberg (HW) principle explains how random mating (RM) can produce and maintain a population in equilibrium, that is, with constant genotypic proportions. When proportions diverge from HW form, it is of interest to estimate the fixation index F, which reflects the degree of divergence. Starting from a sample of genotypic counts, a mixed procedure gives first the orthodox estimate of gene frequency q and then a Bayesian estimate of F, based on a credible prior distribution of F, which is described here.

Determination of the influence of dispersion pattern of pesticide-resistant individuals on the reliability of resistance estimates using different sampling plans.

PubMed

Shah, R; Worner, S P; Chapman, R B

2012-10-01

Pesticide resistance monitoring includes resistance detection and subsequent documentation/ measurement. Resistance detection would require at least one (≥1) resistant individual(s) to be present in a sample to initiate management strategies. Resistance documentation, on the other hand, would attempt to get an estimate of the entire population (≥90%) of the resistant individuals. A computer simulation model was used to compare the efficiency of simple random and systematic sampling plans to detect resistant individuals and to document their frequencies when the resistant individuals were randomly or patchily distributed. A patchy dispersion pattern of resistant individuals influenced the sampling efficiency of systematic sampling plans while the efficiency of random sampling was independent of such patchiness. When resistant individuals were randomly distributed, sample sizes required to detect at least one resistant individual (resistance detection) with a probability of 0.95 were 300 (1%) and 50 (10% and 20%); whereas, when resistant individuals were patchily distributed, using systematic sampling, sample sizes required for such detection were 6000 (1%), 600 (10%) and 300 (20%). Sample sizes of 900 and 400 would be required to detect ≥90% of resistant individuals (resistance documentation) with a probability of 0.95 when resistant individuals were randomly dispersed and present at a frequency of 10% and 20%, respectively; whereas, when resistant individuals were patchily distributed, using systematic sampling, a sample size of 3000 and 1500, respectively, was necessary. Small sample sizes either underestimated or overestimated the resistance frequency. A simple random sampling plan is, therefore, recommended for insecticide resistance detection and subsequent documentation.

Osteoporosis and vertebral fractures in men aged 60-74 years.

PubMed

Frost, Morten; Wraae, Kristian; Abrahamsen, Bo; Høiberg, Mikkel; Hagen, Claus; Andersen, Marianne; Brixen, Kim

2012-03-01

limited information on the prevalence of osteoporosis and VFxs in men in high-risk populations is available. The choice of reference values for dual X-ray absorptiometry (DXA) is debated. We evaluated the prevalence of osteoporosis and vertebral deformities in a population-based sample of men. bone mineral density (BMD) was measured and vertebral deformities assessed using DXA and VFx assessment (VFA), respectively, in a random sample of 600 Danish men aged 60-74 years. Osteoporosis was defined as a T-score of -2.5 or less. the study population was comparable with the background population with regard to age, body mass index and co-morbidity. Osteoporosis was diagnosed in less than 1% of the participants at inclusion. Using Danish and NHANES III reference data, 10.2 and 11.5% of the study population had osteoporosis, respectively. In all, 6.3% participants had at least one VFx. BMD was significantly lower in participants with vertebral deformities, but only 24% of these cases had osteoporosis. osteoporosis and VFxs are prevalent in men aged 60-74 years. Although the majority of deformities were present in individuals without osteoporosis, BMD was lower in patients with VFxs at all sites investigated. Male osteoporosis was markedly underdiagnosed.

Reliability of N-terminal proBNP assay in diagnosis of left ventricular systolic dysfunction within representative and high risk populations.

PubMed

Hobbs, F D R; Davis, R C; Roalfe, A K; Hare, R; Davies, M K

2004-08-01

To determine the performance of a new NT-proBNP assay in comparison with brain natriuretic peptide (BNP) in identifying left ventricular systolic dysfunction (LVSD) in randomly selected community populations. Blood samples were taken prospectively in the community from 591 randomly sampled individuals over the age of 45 years, stratified for age and socioeconomic status and divided into four cohorts (general population; clinically diagnosed heart failure; patients on diuretics; and patients deemed at high risk of heart failure). Definite heart failure (left ventricular ejection fraction (LVEF) < 40%) was identified in 33 people. Samples were handled as though in routine clinical practice. The laboratories undertaking the assays were blinded. Using NT-proBNP to diagnose LVEF < 40% in the general population, a level of > 40 pmol/l had 80% sensitivity, 73% specificity, 5% positive predictive value (PPV), 100% negative predictive value (NPV), and an area under the receiver-operator characteristic curve (AUC) of 76% (95% confidence interval (CI) 46% to 100%). For BNP to diagnose LVSD, a cut off level of > 33 pmol/l had 80% sensitivity, 88% specificity, 10% PPV, 100% NPV, and AUC of 88% (95% CI 75% to 100%). Similar NPVs were found for patients randomly screened from the three other populations. Both NT-proBNP and BNP have value in diagnosing LVSD in a community setting, with similar sensitivities and specificities. Using a high cut off for positivity will confirm the diagnosis of LVSD but will miss cases. At lower cut off values, positive results will require cardiac imaging to confirm LVSD.

Sample Size Calculations for Population Size Estimation Studies Using Multiplier Methods With Respondent-Driven Sampling Surveys.

PubMed

Fearon, Elizabeth; Chabata, Sungai T; Thompson, Jennifer A; Cowan, Frances M; Hargreaves, James R

2017-09-14

While guidance exists for obtaining population size estimates using multiplier methods with respondent-driven sampling surveys, we lack specific guidance for making sample size decisions. To guide the design of multiplier method population size estimation studies using respondent-driven sampling surveys to reduce the random error around the estimate obtained. The population size estimate is obtained by dividing the number of individuals receiving a service or the number of unique objects distributed (M) by the proportion of individuals in a representative survey who report receipt of the service or object (P). We have developed an approach to sample size calculation, interpreting methods to estimate the variance around estimates obtained using multiplier methods in conjunction with research into design effects and respondent-driven sampling. We describe an application to estimate the number of female sex workers in Harare, Zimbabwe. There is high variance in estimates. Random error around the size estimate reflects uncertainty from M and P, particularly when the estimate of P in the respondent-driven sampling survey is low. As expected, sample size requirements are higher when the design effect of the survey is assumed to be greater. We suggest a method for investigating the effects of sample size on the precision of a population size estimate obtained using multipler methods and respondent-driven sampling. Uncertainty in the size estimate is high, particularly when P is small, so balancing against other potential sources of bias, we advise researchers to consider longer service attendance reference periods and to distribute more unique objects, which is likely to result in a higher estimate of P in the respondent-driven sampling survey. ©Elizabeth Fearon, Sungai T Chabata, Jennifer A Thompson, Frances M Cowan, James R Hargreaves. Originally published in JMIR Public Health and Surveillance (http://publichealth.jmir.org), 14.09.2017.

Efficient design and inference for multistage randomized trials of individualized treatment policies.

PubMed

Dawson, Ree; Lavori, Philip W

2012-01-01

Clinical demand for individualized "adaptive" treatment policies in diverse fields has spawned development of clinical trial methodology for their experimental evaluation via multistage designs, building upon methods intended for the analysis of naturalistically observed strategies. Because often there is no need to parametrically smooth multistage trial data (in contrast to observational data for adaptive strategies), it is possible to establish direct connections among different methodological approaches. We show by algebraic proof that the maximum likelihood (ML) and optimal semiparametric (SP) estimators of the population mean of the outcome of a treatment policy and its standard error are equal under certain experimental conditions. This result is used to develop a unified and efficient approach to design and inference for multistage trials of policies that adapt treatment according to discrete responses. We derive a sample size formula expressed in terms of a parametric version of the optimal SP population variance. Nonparametric (sample-based) ML estimation performed well in simulation studies, in terms of achieved power, for scenarios most likely to occur in real studies, even though sample sizes were based on the parametric formula. ML outperformed the SP estimator; differences in achieved power predominately reflected differences in their estimates of the population mean (rather than estimated standard errors). Neither methodology could mitigate the potential for overestimated sample sizes when strong nonlinearity was purposely simulated for certain discrete outcomes; however, such departures from linearity may not be an issue for many clinical contexts that make evaluation of competitive treatment policies meaningful.

Does sampling using random digit dialling really cost more than sampling from telephone directories: Debunking the myths

PubMed Central

Yang, Baohui; Eyeson-Annan, Margo

2006-01-01

Background Computer assisted telephone interviewing (CATI) is widely used for health surveys. The advantages of CATI over face-to-face interviewing are timeliness and cost reduction to achieve the same sample size and geographical coverage. Two major CATI sampling procedures are used: sampling directly from the electronic white pages (EWP) telephone directory and list assisted random digit dialling (LA-RDD) sampling. EWP sampling covers telephone numbers of households listed in the printed white pages. LA-RDD sampling has a better coverage of households than EWP sampling but is considered to be more expensive due to interviewers dialling more out-of-scope numbers. Methods This study compared an EWP sample and a LA-RDD sample from the New South Wales Population Health Survey in 2003 on demographic profiles, health estimates, coefficients of variation in weights, design effects on estimates, and cost effectiveness, on the basis of achieving the same level of precision of estimates. Results The LA-RDD sample better represented the population than the EWP sample, with a coefficient of variation of weights of 1.03 for LA-RDD compared with 1.21 for EWP, and average design effects of 2.00 for LA-RDD compared with 2.38 for EWP. Also, a LA-RDD sample can save up to 14.2% in cost compared to an EWP sample to achieve the same precision for health estimates. Conclusion A LA-RDD sample better represents the population, which potentially leads to reduced bias in health estimates, and rather than costing more than EWP actually costs less. PMID:16504117

Examination of participant flow in the CONSORT diagram can improve the understanding of the generalizability of study results.

PubMed

Andrade, Chittaranjan

2015-11-01

A fundamental principle in research is that the findings of a study can only be generalized to the population from which the sample of the study was drawn. What this population was can be discerned from an examination of the study selection criteria. Additional insights can sometimes be gleaned from the study flowchart or CONSORT diagram, which may show sample attenuation between subject screening and final recruitment. Such sample attenuation, if present, implies further limitation to the generalizability of the study outcomes. Two large, 2-year, randomized controlled maintenance therapy trials are described to illustrate sample attenuation that limits study generalizability, one in the context of mindfulness-based cognitive therapy versus antidepressant drugs for recurrent major depressive disorder and the other in the context of quetiapine versus placebo for bipolar disorder. Readers therefore need to examine both study selection criteria and the CONSORT diagram in order to better understand the extent to which study results apply to the patients whom they see. © Copyright 2015 Physicians Postgraduate Press, Inc.

Randomly amplified polymorphic DNA linkage relationships in different Norway spruce populations

Treesearch

M. Troggio; Thomas L. Kubisiak; G. Bucci; P. Menozzi

2001-01-01

We tested the constancy of linkage relationships of randomly amplified polymorphic DNA (RAPD) marker loci used to construct a population-based consensus map in material from an Italian stand of Picea abies (L.) Karst. in 29 individuals from three Norwegian populations. Thirteen marker loci linked in the Italian stand did show a consistent locus...

Finite-sample corrected generalized estimating equation of population average treatment effects in stepped wedge cluster randomized trials.

PubMed

Scott, JoAnna M; deCamp, Allan; Juraska, Michal; Fay, Michael P; Gilbert, Peter B

2017-04-01

Stepped wedge designs are increasingly commonplace and advantageous for cluster randomized trials when it is both unethical to assign placebo, and it is logistically difficult to allocate an intervention simultaneously to many clusters. We study marginal mean models fit with generalized estimating equations for assessing treatment effectiveness in stepped wedge cluster randomized trials. This approach has advantages over the more commonly used mixed models that (1) the population-average parameters have an important interpretation for public health applications and (2) they avoid untestable assumptions on latent variable distributions and avoid parametric assumptions about error distributions, therefore, providing more robust evidence on treatment effects. However, cluster randomized trials typically have a small number of clusters, rendering the standard generalized estimating equation sandwich variance estimator biased and highly variable and hence yielding incorrect inferences. We study the usual asymptotic generalized estimating equation inferences (i.e., using sandwich variance estimators and asymptotic normality) and four small-sample corrections to generalized estimating equation for stepped wedge cluster randomized trials and for parallel cluster randomized trials as a comparison. We show by simulation that the small-sample corrections provide improvement, with one correction appearing to provide at least nominal coverage even with only 10 clusters per group. These results demonstrate the viability of the marginal mean approach for both stepped wedge and parallel cluster randomized trials. We also study the comparative performance of the corrected methods for stepped wedge and parallel designs, and describe how the methods can accommodate interval censoring of individual failure times and incorporate semiparametric efficient estimators.

A novel approach to evaluation of pest insect abundance in the presence of noise.

PubMed

Embleton, Nina; Petrovskaya, Natalia

2014-03-01

Evaluation of pest abundance is an important task of integrated pest management. It has recently been shown that evaluation of pest population size from discrete sampling data can be done by using the ideas of numerical integration. Numerical integration of the pest population density function is a computational technique that readily gives us an estimate of the pest population size, where the accuracy of the estimate depends on the number of traps installed in the agricultural field to collect the data. However, in a standard mathematical problem of numerical integration, it is assumed that the data are precise, so that the random error is zero when the data are collected. This assumption does not hold in ecological applications. An inherent random error is often present in field measurements, and therefore it may strongly affect the accuracy of evaluation. In our paper, we offer a novel approach to evaluate the pest insect population size under the assumption that the data about the pest population include a random error. The evaluation is not based on statistical methods but is done using a spatially discrete method of numerical integration where the data obtained by trapping as in pest insect monitoring are converted to values of the population density. It will be discussed in the paper how the accuracy of evaluation differs from the case where the same evaluation method is employed to handle precise data. We also consider how the accuracy of the pest insect abundance evaluation can be affected by noise when the data available from trapping are sparse. In particular, we show that, contrary to intuitive expectations, noise does not have any considerable impact on the accuracy of evaluation when the number of traps is small as is conventional in ecological applications.

Pre-Survey Text Messages (SMS) Improve Participation Rate in an Australian Mobile Telephone Survey: An Experimental Study.

PubMed

Dal Grande, Eleonora; Chittleborough, Catherine Ruth; Campostrini, Stefano; Dollard, Maureen; Taylor, Anne Winifred

2016-01-01

Mobile telephone numbers are increasingly being included in household surveys samples. As approach letters cannot be sent because many do not have address details, alternatives approaches have been considered. This study assesses the effectiveness of sending a short message service (SMS) to a random sample of mobile telephone numbers to increase response rates. A simple random sample of 9000 Australian mobile telephone numbers: 4500 were randomly assigned to be sent a pre-notification SMS, and the remaining 4500 did not have a SMS sent. Adults aged 18 years and over, and currently in paid employment, were eligible to participate. American Association for Public Opinion Research formulas were used to calculated response cooperation and refusal rates. Response and cooperation rate were higher for the SMS groups (12.4% and 28.6% respectively) than the group with no SMS (7.7% and 16.0%). Refusal rates were lower for the SMS group (27.3%) than the group with no SMS (35.9%). When asked, 85.8% of the pre-notification group indicated they remembered receiving a SMS about the study. Sending a pre-notification SMS is effective in improving participation in population-based surveys. Response rates were increased by 60% and cooperation rates by 79%.

Obesity, diabetes, hypertension, and vegetarian status among Seventh-Day Adventists in Barbados: preliminary results.

PubMed

Brathwaite, Noel; Fraser, Henry S; Modeste, Naomi; Broome, Hedy; King, Rosaline

2003-01-01

A population-based sample of Seventh-Day Adventists was studied to determine the relationship between vegetarian status, body mass index (BMI), obesity, diabetes mellitus (DM), and hypertension, in order to gain a better understanding of factors influencing chronic diseases in Barbados. A systematic sampling from a random start technique was used to select participants for the study. A standard questionnaire was used to collect data on demographic and lifestyle characteristics, to record anthropometrics and blood pressure measurements, and to ascertain the hypertension and diabetes status of participants. The sample population consisted of 407 Barbadian Seventh-Day Adventists (SDAs), who ranged in age from 25 to 74 years. One hundred fifty-three (37.6%) participants were male, and 254 (62.4%) were female, and 43.5% were vegetarians. The prevalence rates of diabetes and hypertension were lower among long-term vegetarians, compared to non-vegetarians, and long-term vegetarians were, on average, leaner than non-vegetarians within the same cohort. A significant association was observed between a vegetarian diet and obesity (vegetarian by definition P=.04, self-reported vegetarian P=.009) in this population. Other components of the study population lifestyle should be further analyzed to determine the roles they may plan in lessening the prevalence rates of obesity, diabetes, and hypertension.

Risk factors for psychopathology in children with intellectual disability: a prospective longitudinal population-based study.

PubMed

Wallander, J L; Dekker, M C; Koot, H M

2006-04-01

This study examined risk factors for the development of psychopathology in children with intellectual disability (ID) in the developmental, biological, family and social-ecological domains. A population sample of 968 children, aged 6-18, enrolled in special schools in The Netherlands for educable and trainable ID were assessed at Time 1. A random 58% were re-contacted about 1 year later, resulting in a sample of 474 at Time 2. Psychopathology was highly consistent over 1 year. Risk factors jointly accounted for significant, but small, portions of the variance in development of psychopathology. Child physical symptoms, family dysfunction and previous parental mental health treatment reported at Time 1 were uniquely associated with new psychopathology at Time 2. Prevention and early intervention research to find ways to reduce the incidence of psychopathology, possibly targeting family functioning, appear important.

Pollution gets personal! A first population-based human biomonitoring study in Austria.

PubMed

Hohenblum, Philipp; Steinbichl, Philipp; Raffesberg, Wolfgang; Weiss, Stefan; Moche, Wolfgang; Vallant, Birgit; Scharf, Sigrid; Haluza, Daniela; Moshammer, Hanns; Kundi, Michael; Piegler, Brigitte; Wallner, Peter; Hutter, Hans-Peter

2012-02-01

Humans are exposed to a broad variety of man-made chemicals. Human biomonitoring (HBM) data reveal the individual body burden irrespective of sources and routes of uptake. A first population-based study was started in Austria in 2008 and was finished at the end of May 2011. This cross sectional study aims at documenting the extent, the distribution and the determinants of human exposure to industrial chemicals as well as proving the feasibility of a representative HBM study. Overall, 150 volunteers (50 families) were selected by stratified random sampling. Exposure to phthalates, trisphosphates, polybrominated diphenyl ethers (PBDE), bisphenol A (along with nonyl- and octyl phenol) and methyl mercury was assessed. Sixteen of 18 PBDE determined were detected above the limit of quantification (LOQ) in blood samples with #153 and #197 the most abundant species. Bisphenol A in urine was measured in a subsample of 25 with only 4 samples found above the LOQ. In 3 of 100 urine samples at least one of 8 trisphosphate compounds assessed was above the LOQ. These first analytical results of the human biomonitoring data show that the body burden of the Austrian population with respect to the assessed compounds is comparable to or even lower than in other European countries. Overall, the study revealed that in order to develop a feasible protocol for representative human biomonitoring studies procedures have to be optimized to allow for non-invasive sampling of body tissues in accordance with the main metabolic pathways. Procedures of participants' recruitment were, however, labor intensive and have to be improved. Copyright © 2011 Elsevier GmbH. All rights reserved.

E-Rehabilitation - an Internet and mobile phone based tailored intervention to enhance self-management of cardiovascular disease: study protocol for a randomized controlled trial.

PubMed

Antypas, Konstantinos; Wangberg, Silje C

2012-07-09

Cardiac rehabilitation is very important for the recovery and the secondary prevention of cardiovascular disease, and one of its main strategies is to increase the level of physical activity. Internet and mobile phone based interventions have been successfully used to help people to achieve this. One of the components that are related to the efficacy of these interventions is tailoring of content to the individual. This trial is studying the effect of a longitudinally tailored Internet and mobile phone based intervention that is based on models of health behaviour, on the level of physical activity and the adherence to the intervention, as an extension of a face-to-face cardiac rehabilitation stay. A parallel group, cluster randomized controlled trial. The study population is adult participants of a cardiac rehabilitation programme in Norway with home Internet access and mobile phone, who in monthly clusters are randomized to the control or the intervention condition. Participants have access to a website with information regarding cardiac rehabilitation, an online discussion forum and an online activity calendar. Those randomized to the intervention condition, receive in addition tailored content based on models of health behaviour, through the website and mobile text messages. The objective is to assess the effect of the intervention on maintenance of self-management behaviours after the rehabilitation stay. Main outcome is the level of physical activity one month, three months and one year after the end of the cardiac rehabilitation programme. The randomization of clusters is based on a true random number online service, and participants, investigators and outcome assessor are blinded to the condition of the clusters. The study suggests a theory-based intervention that combines models of health behaviour in an innovative way, in order to tailor the delivered content. The users have been actively involved in its design, and because of the use of Open-Source software, the intervention can easily and at low-cost be reproduced and expanded by others. Challenges are the recruitment in the elderly population and the possible underrepresentation of women in the study sample. Funding by Northern Norway Regional Health Authority. Trial registry http://www.clinicaltrials.gov: NCT01223170.

Sample size of the reference sample in a case-augmented study.

PubMed

Ghosh, Palash; Dewanji, Anup

2017-05-01

The case-augmented study, in which a case sample is augmented with a reference (random) sample from the source population with only covariates information known, is becoming popular in different areas of applied science such as pharmacovigilance, ecology, and econometrics. In general, the case sample is available from some source (for example, hospital database, case registry, etc.); however, the reference sample is required to be drawn from the corresponding source population. The required minimum size of the reference sample is an important issue in this regard. In this work, we address the minimum sample size calculation and discuss related issues. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Sampling intraspecific variability in leaf functional traits: Practical suggestions to maximize collected information.

PubMed

Petruzzellis, Francesco; Palandrani, Chiara; Savi, Tadeja; Alberti, Roberto; Nardini, Andrea; Bacaro, Giovanni

2017-12-01

The choice of the best sampling strategy to capture mean values of functional traits for a species/population, while maintaining information about traits' variability and minimizing the sampling size and effort, is an open issue in functional trait ecology. Intraspecific variability (ITV) of functional traits strongly influences sampling size and effort. However, while adequate information is available about intraspecific variability between individuals (ITV BI ) and among populations (ITV POP ), relatively few studies have analyzed intraspecific variability within individuals (ITV WI ). Here, we provide an analysis of ITV WI of two foliar traits, namely specific leaf area (SLA) and osmotic potential (π), in a population of Quercus ilex L. We assessed the baseline ITV WI level of variation between the two traits and provided the minimum and optimal sampling size in order to take into account ITV WI , comparing sampling optimization outputs with those previously proposed in the literature. Different factors accounted for different amount of variance of the two traits. SLA variance was mostly spread within individuals (43.4% of the total variance), while π variance was mainly spread between individuals (43.2%). Strategies that did not account for all the canopy strata produced mean values not representative of the sampled population. The minimum size to adequately capture the studied functional traits corresponded to 5 leaves taken randomly from 5 individuals, while the most accurate and feasible sampling size was 4 leaves taken randomly from 10 individuals. We demonstrate that the spatial structure of the canopy could significantly affect traits variability. Moreover, different strategies for different traits could be implemented during sampling surveys. We partially confirm sampling sizes previously proposed in the recent literature and encourage future analysis involving different traits.

Feline mitochondrial DNA sampling for forensic analysis: when enough is enough!

PubMed

Grahn, Robert A; Alhaddad, Hasan; Alves, Paulo C; Randi, Ettore; Waly, Nashwa E; Lyons, Leslie A

2015-05-01

Pet hair has a demonstrated value in resolving legal issues. Cat hair is chronically shed and it is difficult to leave a home with cats without some level of secondary transfer. The power of cat hair as an evidentiary resource may be underused because representative genetic databases are not available for exclusionary purposes. Mitochondrial control region databases are highly valuable for hair analyses and have been developed for the cat. In a representative worldwide data set, 83% of domestic cat mitotypes belong to one of twelve major types. Of the remaining 17%, 7.5% are unique within the published 1394 sample database. The current research evaluates the sample size necessary to establish a representative population for forensic comparison of the mitochondrial control region for the domestic cat. For most worldwide populations, randomly sampling 50 unrelated local individuals will achieve saturation at 95%. The 99% saturation is achieved by randomly sampling 60-170 cats, depending on the numbers of mitotypes available in the population at large. Likely due to the recent domestication of the cat and minimal localized population substructure, fewer cats are needed to meet mitochondria DNA control region database practical saturation than for humans or dogs. Coupled with the available worldwide feline control region database of nearly 1400 cats, minimal local sampling will be required to establish an appropriate comparative representative database and achieve significant exclusionary power. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

The revised Temperament and Character Inventory: normative data by sex and age from a Spanish normal randomized sample

PubMed Central

Labad, Javier; Martorell, Lourdes; Gaviria, Ana; Bayón, Carmen; Vilella, Elisabet; Cloninger, C. Robert

2015-01-01

Objectives. The psychometric properties regarding sex and age for the revised version of the Temperament and Character Inventory (TCI-R) and its derived short version, the Temperament and Character Inventory (TCI-140), were evaluated with a randomized sample from the community. Methods. A randomized sample of 367 normal adult subjects from a Spanish municipality, who were representative of the general population based on sex and age, participated in the current study. Descriptive statistics and internal consistency according to α coefficient were obtained for all of the dimensions and facets. T-tests and univariate analyses of variance, followed by Bonferroni tests, were conducted to compare the distributions of the TCI-R dimension scores by age and sex. Results. On both the TCI-R and TCI-140, women had higher scores for Harm Avoidance, Reward Dependence and Cooperativeness than men, whereas men had higher scores for Persistence. Age correlated negatively with Novelty Seeking, Reward Dependence and Cooperativeness and positively with Harm Avoidance and Self-transcendence. Young subjects between 18 and 35 years had higher scores than older subjects in NS and RD. Subjects between 51 and 77 years scored higher in both HA and ST. The alphas for the dimensions were between 0.74 and 0.87 for the TCI-R and between 0.63 and 0.83 for the TCI-140. Conclusion. Results, which were obtained with a randomized sample, suggest that there are specific distributions of personality traits by sex and age. Overall, both the TCI-R and the abbreviated TCI-140 were reliable in the ‘good-to-excellent’ range. A strength of the current study is the representativeness of the sample. PMID:26713237

Can we use postal surveys with anonymous testing to monitor chlamydia prevalence in young women in England? Pilot study incorporating randomised controlled trial of recruitment methods.

PubMed

Woodhall, Sarah C; Nichols, Tom; Alexander, Sarah; da Silva, Filomeno Coelho; Mercer, Catherine H; Ison, Catherine; Gill, O Noel; Soldan, Kate

2015-09-01

Chlamydia prevalence in the general population is a potential outcome measure for the evaluation of chlamydia control programmes. We carried out a pilot study to determine the feasibility of using a postal survey for population-based chlamydia prevalence monitoring. Postal invitations were sent to a random sample of 2000 17-year-old to 18-year-old women registered with a general practitioner in two pilot areas in England. Recipients were randomised to receive either a self-sampling kit (n=1000), a self-sampling kit and offer of £5 voucher on return of sample (n=500) or a self-sampling kit on request (n=500). Participants returned a questionnaire and self-taken vulvovaginal swab sample for unlinked anonymous Chlamydia trachomatis testing. Non-responders were sent a reminder letter 3 weeks after initial invitation. We calculated the participation rate (number of samples returned/number of invitations sent) and cost per sample returned (including cost of consumables and postage) in each group. A total of 155/2000 (7.8%) samples were returned with consent for testing. Participation rates varied by invitation group: 7.8% in the group who were provided with a self-sampling kit, 14% in the group who were also offered a voucher and 1.0% in the group who were not sent a kit. The cost per sample received was lowest (£36) in the group who were offered both a kit and a voucher. The piloted survey methodology achieved low participation rates. This approach is not suitable for population-based monitoring of chlamydia prevalence among young women in England. (UKCRN ID 10913). Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

A randomized trial of tailoring and motivational interviewing to promote fruit and vegetable consumption for cancer prevention and control.

PubMed

Campbell, Marci Kramish; Carr, Carol; Devellis, Brenda; Switzer, Boyd; Biddle, Andrea; Amamoo, M Ahinee; Walsh, Joan; Zhou, Bingqing; Sandler, Robert

2009-10-01

Healthful dietary patterns, including eating fruits and vegetables (F&V) and avoiding obesity, may decrease the risk of cancer and other chronic diseases. In addition to promoting health for the general population, a cancer diagnosis may provide a "teachable moment," facilitating the adoption of more healthful eating habits and leading to lower risk of chronic disease and better overall health. This study was designed to test the effectiveness of two health communication interventions in increasing F&V consumption and physical activity in a sample of older adults (average age of 66 years), including both colorectal cancer (CRC) survivors and noncolorectal cancer-affected (N-CRC) individuals. CRC survivors and N-CRC individuals were recruited from a population-based case-control study and randomly assigned to four conditions using a 2 x 2 design. We tested two different methods of communicating and promoting health behavior change alone or in combination: tailored print communication (TPC) and brief telephone-based motivational interviewing (TMI). A significant increase in F&V consumption was found for the combined intervention group in the entire sample (p < 0.05). When stratified by cancer survivor status, the effect was concentrated in the N-CRC subset (p < 0.01) versus CRC survivors. The combined intervention was also found to be most cost-effective for the N-CRC group, with TPC more cost-effective than TMI. For physical activity, none of the interventions produced statistically significant improvements. This study indicates that combining tailoring and motivational interviewing may be an effective and cost-effective method for promoting dietary behavior change among older healthy adults. More research is needed to identify the optimal dose and timing for intervention strategies to promote dietary and physical activity change among both CRC survivors and the general population.

Towards the Development of a More Accurate Monitoring Procedure for Invertebrate Populations, in the Presence of an Unknown Spatial Pattern of Population Distribution in the Field

PubMed Central

Petrovskaya, Natalia B.; Forbes, Emily; Petrovskii, Sergei V.; Walters, Keith F. A.

2018-01-01

Studies addressing many ecological problems require accurate evaluation of the total population size. In this paper, we revisit a sampling procedure used for the evaluation of the abundance of an invertebrate population from assessment data collected on a spatial grid of sampling locations. We first discuss how insufficient information about the spatial population density obtained on a coarse sampling grid may affect the accuracy of an evaluation of total population size. Such information deficit in field data can arise because of inadequate spatial resolution of the population distribution (spatially variable population density) when coarse grids are used, which is especially true when a strongly heterogeneous spatial population density is sampled. We then argue that the average trap count (the quantity routinely used to quantify abundance), if obtained from a sampling grid that is too coarse, is a random variable because of the uncertainty in sampling spatial data. Finally, we show that a probabilistic approach similar to bootstrapping techniques can be an efficient tool to quantify the uncertainty in the evaluation procedure in the presence of a spatial pattern reflecting a patchy distribution of invertebrates within the sampling grid. PMID:29495513

Is Knowledge Random? Introducing Sampling and Bias through Outdoor Inquiry

ERIC Educational Resources Information Center

Stier, Sam

2010-01-01

Sampling, very generally, is the process of learning about something by selecting and assessing representative parts of that population or object. In the inquiry activity described here, students learned about sampling techniques as they estimated the number of trees greater than 12 cm dbh (diameter at breast height) in a wooded, discrete area…

[Environmental Education Units.

ERIC Educational Resources Information Center

Minneapolis Independent School District 275, Minn.

Two of these three pamphlets describe methods of teaching young elementary school children the principles of sampling. Tiles of five colors are added to a tub and children sample these randomly; using the tiles as units for a graph, they draw a representation of the population. Pooling results leads to a more reliable sample. Practice is given in…

Prevalence and determinants of type 2 diabetes mellitus in a Greek adult population.

PubMed

Tsirona, Sofia; Katsaros, Fotis; Bargiota, Alexandra; Polyzos, Stergios A; Arapoglou, George; Koukoulis, George N

2016-01-01

The prevalence of diabetes mellitus (DM) is increasing worldwide reaching epidemic proportions. The aim of the present study was to estimate the prevalence of DM in Thessaly, a large region of Central Greece, and to extrapolate our results to the population of the entire country. A random sample of 805 adults (421 females and 384 men) living in Thessaly, aged 18-80 years, was surveyed. After completing a questionnaire about health status and a thorough physical examination, a blood sample was obtained from each participant for biochemical analysis. Participants with fasting glucose levels between 100-125 mg/dl underwent an oral glucose tolerance test (OGTT). A second survey was also conducted, via telephone call-interviews, in a randomly selected sample age- and sex-stratified to the country's adult population in order to extrapolate the DM data from Thessaly to the whole country. The frequency of DM based on patient history and fasting blood glucose levels was 6.96%, comparable to that observed in the telephone-based nationwide survey (7.38%, p=0.669). However, after the OGTT an additional 3.72% of the population had undiagnosed DM, increasing DM prevalence to 10.68% (age adjusted 11.77%). The prevalence of pre-diabetes was 8.70%, with impaired fasting glucose at 5.84% and impaired glucose tolerance at 2.86%. The prevalence of DM was significantly higher in men (14.58%) than in women (7.13%, p<0.001), increased with age in both sexes and was more prevalent in hypertensive (p<0.001) and obese subjects (p=0.001) and in those living in rural areas (p=0.003). In the multiple logistic regression analysis, significant predictors of pre-diabetes and DM together were age, homeostasis model of assessment of insulin resistance (HOMA-IR), alcohol consumption and educational status, whereas those of DM alone were age, HOMA-IR and triglycerides. Extrapolating our data to the whole country, the age-adjusted prevalence of DM was estimated at 11.97% (men 13.98%, women 9.25%), clearly indicating a major public health problem.

Origin of magnetization in lunar breccias - An example of thermal overprinting

NASA Technical Reports Server (NTRS)

Gose, W. A.; Strangway, D. W.; Pearce, G. W.

1978-01-01

Twenty six samples from seven hand specimens, collected from the station 6 boulder at the Apollo 17 landing site, were studied magnetically. The boulder is a breccia consisting of three lithologic units distinguished by their clast population. The direction of magnetization of samples from unit B which is almost devoid of large clasts cluster fairly well after alternating field demagnetization. Samples from unit C which is characterized by abundant large clasts up to 1 m in size do not contain a uniform direction of magnetization but the distribution is not random. Based on these data we propose that the natural remanent magnetization (NRM) in these breccias is the vector sum of two magnetizations, a pre-impact magnetization and a partial thermoremanence acquired during breccia formation. The relative contribution of the two components is controlled by the thermal history of the ejecta, which in turn is determined by its clast population. Depending on the clast population, the NRM can be a total thermoremanence, a partial thermoremanence plus a pre-impact magnetization, or a pre-impact magnetization. This model of thermal overprinting might be applicable to all lunar breccias of medium and higher metamorphic grade.

Republic of Georgia estimates for prevalence of drug use: Randomized response techniques suggest under-estimation.

PubMed

Kirtadze, Irma; Otiashvili, David; Tabatadze, Mzia; Vardanashvili, Irina; Sturua, Lela; Zabransky, Tomas; Anthony, James C

2018-06-01

Validity of responses in surveys is an important research concern, especially in emerging market economies where surveys in the general population are a novelty, and the level of social control is traditionally higher. The Randomized Response Technique (RRT) can be used as a check on response validity when the study aim is to estimate population prevalence of drug experiences and other socially sensitive and/or illegal behaviors. To apply RRT and to study potential under-reporting of drug use in a nation-scale, population-based general population survey of alcohol and other drug use. For this first-ever household survey on addictive substances for the Country of Georgia, we used the multi-stage probability sampling of 18-to-64-year-old household residents of 111 urban and 49 rural areas. During the interviewer-administered assessments, RRT involved pairing of sensitive and non-sensitive questions about drug experiences. Based upon the standard household self-report survey estimate, an estimated 17.3% [95% confidence interval, CI: 15.5%, 19.1%] of Georgian household residents have tried cannabis. The corresponding RRT estimate was 29.9% [95% CI: 24.9%, 34.9%]. The RRT estimates for other drugs such as heroin also were larger than the standard self-report estimates. We remain unsure about what is the "true" value for prevalence of using illegal psychotropic drugs in the Republic of Georgia study population. Our RRT results suggest that standard non-RRT approaches might produce 'under-estimates' or at best, highly conservative, lower-end estimates. Copyright © 2018 Elsevier B.V. All rights reserved.

High-risk HPV infection after five years in a population-based cohort of Chilean women

PubMed Central

2011-01-01

Background The need to review cervical cancer prevention strategies has been triggered by the availability of new prevention tools linked to human papillomavirus (HPV): vaccines and screening tests. To consider these innovations, information on HPV type distribution and natural history is necessary. This is a five-year follow-up study of gynecological high-risk (HR) HPV infection among a Chilean population-based cohort of women. Findings A population-based random sample of 969 women from Santiago, Chile aged 17 years or older was enrolled in 2001 and revisited in 2006. At both visits they answered a survey on demographics and sexual history and provided a cervical sample for HPV DNA detection (GP5+/6+ primer-mediated PCR and Reverse line blot genotyping). Follow-up was completed by 576 (59.4%) women; 45 (4.6%) refused participation; most losses to follow-up were women who were unreachable, no longer eligible or had missing samples. HR-HPV prevalence increased by 43%. Incidence was highest in women < 20 years of age (19.4%) and lowest in women > 70 (0%); it was three times higher among women HR-HPV positive versus HPV negative at baseline (25.5% and 8.3%; OR 3.8, 95% CI 1.8-8.0). Type-specific persistence was 35.3%; it increased with age, from 0% in women < 30 years of age to 100% in women > 70. An enrollment Pap result ASCUS or worse was the only risk factor for being HR-HPV positive at both visits. Conclusions HR-HPV prevalence increased in the study population. All HR-HPV infections in women < 30 years old cleared, supporting the current recommendation of HR-HPV screening for women > 30 years. PMID:22087645

Evaluation of an osteoporosis and fall risk intervention program for community-dwelling elderly. A quasi-experimental study of behavioral modifications.

PubMed

Grahn Kronhed, Ann-Charlotte; Blomberg, Carina; Löfman, Owe; Timpka, Toomas; Möller, Margareta

2006-06-01

Osteoporosis and fall fractures are increasing problems amongst the elderly. The aim of this study was to explore whether combined population-based and individual interventions directed at risk factors for osteoporosis and falls result in behavioral changes in an elderly population. A quasi-experimental design was used for the study. Persons aged >or=65 years were randomly selected in the intervention and control community. An intervention program was managed from the primary health care center and delivered to the community. Health education was designed to increase awareness of risk factors for the development of osteoporosis and falling. Questionnaires about lifestyle, health, previous fractures, safety behavior and physical activity level were distributed at baseline in 1989 and at the follow-ups in 1992 and 1994 in both communities. There was a difference of 17.7% between the dual intervention (receiving both population-based and individual interventions) and the control samples regarding the self-reported use of shoe/cane spikes, and a difference of 20.5% regarding the reported "moderate level" of physical activity in 1994. There was an increase in the number of participants in the dual intervention sample who, at baseline, had not reported equipping their homes with non-slip mats and removing loose rugs but who did report these changes in 1994. The increase in the reported use of shoe/cane spikes in the dual intervention sample was observed mainly for the period 1992-1994. A public health intervention model, including both population-based and individual interventions, can contribute to behavioral changes in the prevention of falls and changed physical activity patterns amongst elderly people.

Genetic distances and phylogenetic trees of different Awassi sheep populations based on DNA sequencing.

PubMed

Al-Atiyat, R M; Aljumaah, R S

2014-08-27

This study aimed to estimate evolutionary distances and to reconstruct phylogeny trees between different Awassi sheep populations. Thirty-two sheep individuals from three different geographical areas of Jordan and the Kingdom of Saudi Arabia (KSA) were randomly sampled. DNA was extracted from the tissue samples and sequenced using the T7 promoter universal primer. Different phylogenetic trees were reconstructed from 0.64-kb DNA sequences using the MEGA software with the best general time reverse distance model. Three methods of distance estimation were then used. The maximum composite likelihood test was considered for reconstructing maximum likelihood, neighbor-joining and UPGMA trees. The maximum likelihood tree indicated three major clusters separated by cytosine (C) and thymine (T). The greatest distance was shown between the South sheep and North sheep. On the other hand, the KSA sheep as an outgroup showed shorter evolutionary distance to the North sheep population than to the others. The neighbor-joining and UPGMA trees showed quite reliable clusters of evolutionary differentiation of Jordan sheep populations from the Saudi population. The overall results support geographical information and ecological types of the sheep populations studied. Summing up, the resulting phylogeny trees may contribute to the limited information about the genetic relatedness and phylogeny of Awassi sheep in nearby Arab countries.

The rationale/design of the Guimarães/Vizela study: a multimodal population-based cohort study to determine global cardiovascular risk and disease.

PubMed

Cunha, Pedro Guimarães; Cotter, Jorge; Oliveira, Pedro; Vila, Isabel; Sousa, Nuno

2014-06-01

Cardiovascular disease and dementia are growing medical and social problems in aging societies. Appropriate knowledge of cardiovascular disease and cognitive decline risk factors (RFs) are critical for global CVR health preventive intervention. Many epidemiological studies use case definition based on data collected/measured in a single visit, a fact that can overestimate prevalence rates and distant from clinical practice demanding criteria. Portugal displays an elevated stroke mortality rate. However, population's global CV risk characterization is limited, namely, considering traditional/nontraditional RF and new intermediate phenotypes of CV and renal disease. Association of hemodynamic variables (pulse wave velocity and central blood pressure) with global CVR stratification, cognitive performance, and kidney disease are practically inexistent at a dwelling population level. After reviewing published data, we designed a population-based cohort study to analyze the prevalence of these cardiovascular RFs and intermediate phenotypes, using random sampling of adult dwellers living in 2 adjacent cities. Strict definition of phenotypes was planned: subjects were observed twice, and several hemodynamic and other biological variables measured at least 3 months apart. Three thousand thirty-eight subjects were enrolled, and extensive data collection (including central and peripheral blood pressure, pulse wave velocity), sample processing, and biobank edification were carried out. One thousand forty-seven cognitive evaluations were performed. Seeking for CV risk reclassification, early identification of subjects at risk, and evidence of early vascular aging and cognitive and renal function decline, using the strict daily clinical practice criteria, will lead to better resource allocation in preventive measures at a population level.

Seroprevalence of Hepatitis B Virus Infection and Its Risk Factors in the West of Iran: A Population-based Study

PubMed Central

Alavian, Seyed Moayed; Tabatabaei, Seyed Vahid; Ghadimi, Teyyeb; Beedrapour, Farzam; Kafi-abad, Sedigheh Amini; Gharehbaghian, Ahmad; Abolghasemi, Hassan

2012-01-01

Introduction: Hepatitis B virus (HBV) infection is a serious global public health problem affecting billions of people globally. The lack of information of its seroprevalence among the general population is an obstacle for formulating effective policies to reduce the burden viral hepatitis. Therefore, this population based serological survey was conducted in Kurdistan province, where no epidemiological data was available to determine the prevalence and risk factors of HBV infection. Methods: 1613 healthy subjects were selected from all districts of Kurdistan province (in the western of Iran) using random cluster sampling. The subjects’ age ranged from 6 to 65 years old. Serum samples were tested for HBcAb, HBsAg and anti-HDV antibody. Screening tests were carried out by the third generation of ELISA. Various risk factors were recorded and multivariate analysis was performed. Results: The prevalence of HBsAg and HBcAb in Kurdistan was before 0.80% (95% CI 0.44; 1.34) and 5.02% (95% CI 4.03; 6.17), respectively. None of HBsAg carriers had positive anti-HDV antibody. Predictors of HBsAg or HBcAb in multivariate analysis were: older age and marriage. We did not find any significant differences between males and females. Conclusion: Our population based study suggests that intrafamilial HBV transmission plays a major role in HBV transmission in Kurdistan province. Furthermore, approximately 5% of general population in this province has prior exposure to HBV and less than 1% is HBsAg carriers. However, we could not find any case of HDV infection among them. PMID:23189228

Explaining the social gradient in sickness absence: a study of a general working population in Sweden.

PubMed

Löve, Jesper; Hensing, Gunnel; Holmgren, Kristina; Torén, Kjell

2013-06-05

Some previous studies have proposed potential explanatory factors for the social gradient in sickness absence. Yet, this research area is still in its infancy and in order to comprise the full range of socioeconomic positions there is a need for studies conducted on random population samples. The main aim of the present study was to investigate if somatic and mental symptoms, mental wellbeing, job strain, and physical work environment could explain the association between low socioeconomic position and belonging to a sample of new cases of sick-listed employees. This study was conducted on one random working population sample (n = 2763) and one sample of newly sick-listed cases of employees (n = 3044), drawn from the same random general population in western Sweden. Explanatory factors were self-rated 'Somatic and mental symptoms', 'Mental well-being', 'job strain', and 'physical work conditions' (i.e. heavy lifting and awkward work postures). Multiple logistic regression analyses were used. Somatic and mental symptoms, mental well-being, and job strain, could not explain the association between socioeconomic position and sickness absence in both women and men. However, physical work conditions explained the total association in women and much of this association in men. In men the gradient between Non-skilled manual OR 1.76 (1.24;2.48) and Skilled manual OR 1.59 (1.10;2.20), both in relation to Higher non-manual, remained unexplained. The present study strengthens the scientific evidence that social differences in physical work conditions seem to comprise a key element of the social gradient in sickness absence, particularly in women. Future studies should try to identify further predictors for this gradient in men.

Growing cell-phone population and noncoverage bias in traditional random digit dial telephone health surveys.

PubMed

Lee, Sunghee; Brick, J Michael; Brown, E Richard; Grant, David

2010-08-01

Examine the effect of including cell-phone numbers in a traditional landline random digit dial (RDD) telephone survey. The 2007 California Health Interview Survey (CHIS). CHIS 2007 is an RDD telephone survey supplementing a landline sample in California with a sample of cell-only (CO) adults. We examined the degree of bias due to exclusion of CO populations and compared a series of demographic and health-related characteristics by telephone usage. When adjusted for noncoverage in the landline sample through weighting, the potential noncoverage bias due to excluding CO adults in landline telephone surveys is diminished. Both CO adults and adults who have both landline and cell phones but mostly use cell phones appear different from other telephone usage groups. Controlling for demographic differences did not attenuate the significant distinctiveness of cell-mostly adults. While careful weighting can mitigate noncoverage bias in landline telephone surveys, the rapid growth of cell-phone population and their distinctive characteristics suggest it is important to include a cell-phone sample. Moreover, the threat of noncoverage bias in telephone health survey estimates could mislead policy makers with possibly serious consequences for their ability to address important health policy issues.

Predictive equations for total lung capacity and residual volume calculated from radiographs in a random sample of the Michigan population.

PubMed Central

Kilburn, K H; Warshaw, R H; Thornton, J C; Thornton, K; Miller, A

1992-01-01

BACKGROUND: Published predicted values for total lung capacity and residual volume are often based on a small number of subjects and derive from different populations from predicted spirometric values. Equations from the only two large studies gave smaller predicted values for total lung capacity than the smaller studies. A large number of subjects have been studied from a population which has already provided predicted values for spirometry and transfer factor for carbon monoxide. METHODS: Total lung capacity was measured from standard posteroanterior and lateral chest radiographs and forced vital capacity by spirometry in a population sample of 771 subjects. Prediction equations were developed for total lung capacity (TLC), residual volume (RV) and RV/TLC in two groups--normal and total. Subjects with signs or symptoms of cardiopulmonary disease were combined with the normal subjects and equations for all subjects were also modelled. RESULTS: Prediction equations for TLC and RV in non-smoking normal men and women were square root transformations which included height and weight but not age. They included a coefficient for duration of smoking in current smokers. The predictive equation for RV/TLC included weight, age, age and duration of smoking for current smokers and ex-smokers of both sexes. For the total population the equations took the same form but the height coefficients and constants were slightly different. CONCLUSION: These population based prediction equations for TLC, RV and RV/TLC provide reference standards in a population that has provided reference standards for spirometry and single breath transfer factor for carbon monoxide. PMID:1412094

Socioeconomic status and prevalence of self-reported diabetes among adults in Tehran: results from a large population-based cross-sectional study (Urban HEART-2).

PubMed

Asadi-Lari, M; Khosravi, A; Nedjat, S; Mansournia, M A; Majdzadeh, R; Mohammad, K; Vaez-Mahdavi, M R; Faghihzadeh, S; Haeri Mehrizi, A A; Cheraghian, B

2016-05-01

Diabetes mellitus is an important public health challenge worldwide. The prevalence of type 2 diabetes varies across countries. The aim of this study is to estimate the prevalence of type 2 diabetes and to determine related factors including socioeconomic factors in a large random sample of Tehran population in 2011. In this cross-sectional study, 91,814 individuals aged over 20 years were selected randomly based on a multistage, cluster sampling. All participants were interviewed by trained personnel using standard questionnaires. Prevalence and Townsend deprivation indexes were calculated. Principal component analysis (PCA) was used to construct wealth index. Logistic regression model was used in multivariate analysis. The estimated prevalence of self-reported diabetes was 4.98 % overall, 4.76 %in men and 5.19 % in women (P < 0.003). In multivariate analysis, age, marital status (married and divorced/widow) and BMI were positively associated with the prevalence of self-reported diabetes. Of the socioeconomic variables, educational level and wealth status were negatively and Townsend Index was positively associated with diabetes. Our study findings highlight low reported prevalence of diabetes among adults in Tehran. Subjects with low socioeconomic status (SES) had a higher prevalence of type 2 diabetes. Weight gain and obesity were the most important risk factors associated with type 2 diabetes. Wealth index and educational level were better socioeconomic indicators for presenting the inequality in diabetes prevalence in relation to Townsend deprivation index.

Identification of countermeasures for the youth crash problem related to alcohol

DOT National Transportation Integrated Search

1975-01-01

Face-to-face interviews were conducted with male New York State drivers. These groups, each containing young (16-24 years) and middle aged (35-49 years) drivers were sampled as follows: 1) random sample of the general population of licensed drivers (...

Faà di Bruno's formula and the distributions of random partitions in population genetics and physics.

PubMed

Hoppe, Fred M

2008-06-01

We show that the formula of Faà di Bruno for the derivative of a composite function gives, in special cases, the sampling distributions in population genetics that are due to Ewens and to Pitman. The composite function is the same in each case. Other sampling distributions also arise in this way, such as those arising from Dirichlet, multivariate hypergeometric, and multinomial models, special cases of which correspond to Bose-Einstein, Fermi-Dirac, and Maxwell-Boltzmann distributions in physics. Connections are made to compound sampling models.

Sampling methods to the statistical control of the production of blood components.

PubMed

Pereira, Paulo; Seghatchian, Jerard; Caldeira, Beatriz; Santos, Paula; Castro, Rosa; Fernandes, Teresa; Xavier, Sandra; de Sousa, Gracinda; de Almeida E Sousa, João Paulo

2017-12-01

The control of blood components specifications is a requirement generalized in Europe by the European Commission Directives and in the US by the AABB standards. The use of a statistical process control methodology is recommended in the related literature, including the EDQM guideline. The control reliability is dependent of the sampling. However, a correct sampling methodology seems not to be systematically applied. Commonly, the sampling is intended to comply uniquely with the 1% specification to the produced blood components. Nevertheless, on a purely statistical viewpoint, this model could be argued not to be related to a consistent sampling technique. This could be a severe limitation to detect abnormal patterns and to assure that the production has a non-significant probability of producing nonconforming components. This article discusses what is happening in blood establishments. Three statistical methodologies are proposed: simple random sampling, sampling based on the proportion of a finite population, and sampling based on the inspection level. The empirical results demonstrate that these models are practicable in blood establishments contributing to the robustness of sampling and related statistical process control decisions for the purpose they are suggested for. Copyright © 2017 Elsevier Ltd. All rights reserved.

Genetic demographic networks: Mathematical model and applications.

PubMed

Kimmel, Marek; Wojdyła, Tomasz

2016-10-01

Recent improvement in the quality of genetic data obtained from extinct human populations and their ancestors encourages searching for answers to basic questions regarding human population history. The most common and successful are model-based approaches, in which genetic data are compared to the data obtained from the assumed demography model. Using such approach, it is possible to either validate or adjust assumed demography. Model fit to data can be obtained based on reverse-time coalescent simulations or forward-time simulations. In this paper we introduce a computational method based on mathematical equation that allows obtaining joint distributions of pairs of individuals under a specified demography model, each of them characterized by a genetic variant at a chosen locus. The two individuals are randomly sampled from either the same or two different populations. The model assumes three types of demographic events (split, merge and migration). Populations evolve according to the time-continuous Moran model with drift and Markov-process mutation. This latter process is described by the Lyapunov-type equation introduced by O'Brien and generalized in our previous works. Application of this equation constitutes an original contribution. In the result section of the paper we present sample applications of our model to both simulated and literature-based demographies. Among other we include a study of the Slavs-Balts-Finns genetic relationship, in which we model split and migrations between the Balts and Slavs. We also include another example that involves the migration rates between farmers and hunters-gatherers, based on modern and ancient DNA samples. This latter process was previously studied using coalescent simulations. Our results are in general agreement with the previous method, which provides validation of our approach. Although our model is not an alternative to simulation methods in the practical sense, it provides an algorithm to compute pairwise distributions of alleles, in the case of haploid non-recombining loci such as mitochondrial and Y-chromosome loci in humans. Copyright © 2016 Elsevier Inc. All rights reserved.

The Association Between Perceived Discrimination and Obesity in a Population-Based Multiracial and Multiethnic Adult Sample

PubMed Central

Williams, David R.

2009-01-01

Objectives. We examined whether perceived chronic discrimination was related to excess body fat accumulation in a random, multiethnic, population-based sample of US adults. Methods. We used multivariate multinomial logistic regression and logistic regression analyses to examine the relationship between interpersonal experiences of perceived chronic discrimination and body mass index and high-risk waist circumference. Results. Consistent with other studies, our analyses showed that perceived unfair treatment was associated with increased abdominal obesity. Compared with Irish, Jewish, Polish, and Italian Whites who did not experience perceived chronic discrimination, Irish, Jewish, Polish, and Italian Whites who perceived chronic discrimination were 2 to 6 times more likely to have a high-risk waist circumference. No significant relationship between perceived discrimination and the obesity measures was found among the other Whites, Blacks, or Hispanics. Conclusions. These findings are not completely unsupported. White ethnic groups including Polish, Italians, Jews, and Irish have historically been discriminated against in the United States, and other recent research suggests that they experience higher levels of perceived discrimination than do other Whites and that these experiences adversely affect their health. PMID:18923119

Framingham risk score for prediction of cardiovascular diseases: a population-based study from southern Europe.

PubMed

Artigao-Rodenas, Luis M; Carbayo-Herencia, Julio A; Divisón-Garrote, Juan A; Gil-Guillén, Vicente F; Massó-Orozco, Javier; Simarro-Rueda, Marta; Molina-Escribano, Francisca; Sanchis, Carlos; Carrión-Valero, Lucinio; López de Coca, Enrique; Caldevilla, David; López-Abril, Juan; Carratalá-Munuera, Concepción; Lopez-Pineda, Adriana

2013-01-01

The question about what risk function should be used in primary prevention remains unanswered. The Framingham Study proposed a new algorithm based on three key ideas: use of the four risk factors with the most weight (cholesterol, blood pressure, diabetes and smoking), prediction of overall cardiovascular diseases and incorporating the concept of vascular age. The objective of this study was to apply this new function in a cohort of the general non Anglo-Saxon population, with a 10-year follow-up to determine its validity. The cohort was studied in 1992-94 and again in 2004-06. The sample comprised 959 randomly-selected persons, aged 30-74 years, who were representative of the population of Albacete, Spain. At the first examination cycle, needed data for the new function were collected and at the second examination, data on all events were recorded during the follow-up period. Discrimination was studied with ROC curves. Comparisons of prediction models and reality in tertiles (Hosmer-Lemeshow) were performed, and the individual survival functions were calculated. The mean risks for women and men, respectively, were 11.3% and 19.7% and the areas under the ROC curve were 0.789 (95%CI, 0.716-0.863) and 0.780 (95%CI, 0.713-0.847) (P<0.001, both). Cardiovascular disease events occurred in the top risk tertiles. Of note were the negative predictive values in both sexes, and a good specificity in women (85.6%) and sensitivity in men (79.1%) when their risk for cardiovascular disease was high. This model overestimates the risk in older women and in middle-aged men. The cumulative probability of individual survival by tertiles was significant in both sexes (P<0.001). The results support the proposal for "reclassification" of Framingham. This study, with a few exceptions, passed the test of discrimination and calibration in a random sample of the general population from southern Europe.

Nonuniform sampling theorems for random signals in the linear canonical transform domain

NASA Astrophysics Data System (ADS)

Shuiqing, Xu; Congmei, Jiang; Yi, Chai; Youqiang, Hu; Lei, Huang

2018-06-01

Nonuniform sampling can be encountered in various practical processes because of random events or poor timebase. The analysis and applications of the nonuniform sampling for deterministic signals related to the linear canonical transform (LCT) have been well considered and researched, but up to now no papers have been published regarding the various nonuniform sampling theorems for random signals related to the LCT. The aim of this article is to explore the nonuniform sampling and reconstruction of random signals associated with the LCT. First, some special nonuniform sampling models are briefly introduced. Second, based on these models, some reconstruction theorems for random signals from various nonuniform samples associated with the LCT have been derived. Finally, the simulation results are made to prove the accuracy of the sampling theorems. In addition, the latent real practices of the nonuniform sampling for random signals have been also discussed.

Environmental Tobacco Smoke and Adult-Onset Asthma: A Population-Based Incident Case–Control Study

PubMed Central

Jaakkola, Maritta S.; Piipari, Ritva; Jaakkola, Niina; Jaakkola, Jouni J. K.

2003-01-01

Objectives. The authors assessed the effects of environmental tobacco smoke (ETS) on the development of asthma in adults. Methods. In the Pirkanmaa district of South Finland, all 21- to 63-year-old adults with new cases of asthma diagnosed during a 2.5-year period (n = 521 case patients, out of 441 000 inhabitants) and a random sample of control subjects from the source population (932 control subjects) participated in a population-based incident case–control study. Results. Risk of asthma was related to workplace ETS exposure (adjusted odds ratio [OR] = 2.16; 95% confidence interval [CI] = 1.26, 3.72) and home exposure (OR = 4.77; 95% CI = 1.29, 17.7) in the past year. Cumulative ETS exposure over a lifetime at work and at home increased the risk. Conclusions. This study indicates for the first time that both cumulative lifetime and recent ETS exposures increase the risk of adult-onset asthma. PMID:14652334

Genarris: Random generation of molecular crystal structures and fast screening with a Harris approximation

NASA Astrophysics Data System (ADS)

Li, Xiayue; Curtis, Farren S.; Rose, Timothy; Schober, Christoph; Vazquez-Mayagoitia, Alvaro; Reuter, Karsten; Oberhofer, Harald; Marom, Noa

2018-06-01

We present Genarris, a Python package that performs configuration space screening for molecular crystals of rigid molecules by random sampling with physical constraints. For fast energy evaluations, Genarris employs a Harris approximation, whereby the total density of a molecular crystal is constructed via superposition of single molecule densities. Dispersion-inclusive density functional theory is then used for the Harris density without performing a self-consistency cycle. Genarris uses machine learning for clustering, based on a relative coordinate descriptor developed specifically for molecular crystals, which is shown to be robust in identifying packing motif similarity. In addition to random structure generation, Genarris offers three workflows based on different sequences of successive clustering and selection steps: the "Rigorous" workflow is an exhaustive exploration of the potential energy landscape, the "Energy" workflow produces a set of low energy structures, and the "Diverse" workflow produces a maximally diverse set of structures. The latter is recommended for generating initial populations for genetic algorithms. Here, the implementation of Genarris is reported and its application is demonstrated for three test cases.

Study protocol for a cluster randomized trial of the Community of Voices choir intervention to promote the health and well-being of diverse older adults.

PubMed

Johnson, Julene K; Nápoles, Anna M; Stewart, Anita L; Max, Wendy B; Santoyo-Olsson, Jasmine; Freyre, Rachel; Allison, Theresa A; Gregorich, Steven E

2015-10-13

Older adults are the fastest growing segment of the United States population. There is an immediate need to identify novel, cost-effective community-based approaches that promote health and well-being for older adults, particularly those from diverse racial/ethnic and socioeconomic backgrounds. Because choral singing is multi-modal (requires cognitive, physical, and psychosocial engagement), it has the potential to improve health outcomes across several dimensions to help older adults remain active and independent. The purpose of this study is to examine the effect of a community choir program (Community of Voices) on health and well-being and to examine its costs and cost-effectiveness in a large sample of diverse, community-dwelling older adults. In this cluster randomized controlled trial, diverse adults age 60 and older were enrolled at Administration on Aging-supported senior centers and completed baseline assessments. The senior centers were randomly assigned to either start the choir immediately (intervention group) or wait 6 months to start (control). Community of Voices is a culturally tailored choir program delivered at the senior centers by professional music conductors that reflects three components of engagement (cognitive, physical, and psychosocial). We describe the nature of the study including the cluster randomized trial study design, sampling frame, sample size calculation, methods of recruitment and assessment, and primary and secondary outcomes. The study involves conducting a randomized trial of an intervention as delivered in "real-world" settings. The choir program was designed using a novel translational approach that integrated evidence-based research on the benefits of singing for older adults, community best practices related to community choirs for older adults, and the perspective of the participating communities. The practicality and relatively low cost of the choir intervention means it can be incorporated into a variety of community settings and adapted to diverse cultures and languages. If successful, this program will be a practical and acceptable community-based approach for promoting health and well-being of older adults. ClinicalTrials.gov NCT01869179 registered 9 January 2013.

A Comparison of the Number of Men Who Have Sex with Men among Rural-To-Urban Migrants with Non-Migrant Rural and Urban Residents in Wuhan, China: A GIS/GPS-Assisted Random Sample Survey Study

PubMed Central

Chen, Xinguang; Yu, Bin; Zhou, Dunjin; Zhou, Wang; Gong, Jie; Li, Shiyue; Stanton, Bonita

2015-01-01

Background Mobile populations and men who have sex with men (MSM) play an increasing role in the current HIV epidemic in China and across the globe. While considerable research has addressed both of these at-risk populations, more effective HIV control requires accurate data on the number of MSM at the population level, particularly MSM among migrant populations. Methods Survey data from a random sample of male rural-to-urban migrants (aged 18-45, n=572) in Wuhan, China were analyzed and compared with those of randomly selected non-migrant urban (n=566) and rural counterparts (580). The GIS/GPS technologies were used for sampling and the survey estimation method was used for data analysis. Results HIV-related risk behaviors among rural-to-urban migrants were similar to those among the two comparison groups. The estimated proportion of MSM among migrants [95% CI] was 5.8% [4.7, 6.8], higher than 2.8% [1.2, 4.5] for rural residents and 1.0% [0.0, 2.4] for urban residents, respectively. Among these migrants, the MSM were more likely than non-MSM to be older in age, married, and migrated to more cities. They were also more likely to co-habit with others in rental properties located in new town and neighborhoods with fewer old acquaintances and more entertainment establishments. In addition, they were more likely to engage in commercial sex and less likely to consistently use condoms. Conclusion Findings of this study indicate that compared to rural and urban populations, the migrant population in Wuhan consists of a higher proportion of MSM who also exhibit higher levels of HIV-related risk behaviors. More effective interventions should target this population with a focus on neighborhood factors, social capital and collective efficacy for risk reduction. PMID:26241900

Proactive tobacco treatment and population-level cessation: a pragmatic randomized clinical trial.

PubMed

Fu, Steven S; van Ryn, Michelle; Sherman, Scott E; Burgess, Diana J; Noorbaloochi, Siamak; Clothier, Barbara; Taylor, Brent C; Schlede, Carolyn M; Burke, Randy S; Joseph, Anne M

2014-05-01

Current tobacco use treatment approaches require smokers to request treatment or depend on the provider to initiate smoking cessation care and are therefore reactive. Most smokers do not receive evidence-based treatments for tobacco use that include both behavioral counseling and pharmacotherapy. To assess the effect of a proactive, population-based tobacco cessation care model on use of evidence-based tobacco cessation treatments and on population-level smoking cessation rates (ie, abstinence among all smokers including those who use and do not use treatment) compared with usual care among a diverse population of current smokers. The Veterans Victory Over Tobacco Study, a pragmatic randomized clinical trial involving a population-based registry of current smokers aged 18 to 80 years. A total of 6400 current smokers, identified using the Department of Veterans Affairs (VA) electronic medical record, were randomized prior to contact to evaluate both the reach and effectiveness of the proactive care intervention. Current smokers were randomized to usual care or proactive care. Proactive care combined (1) proactive outreach and (2) offer of choice of smoking cessation services (telephone or in-person). Proactive outreach included mailed invitations followed by telephone outreach to motivate smokers to seek treatment with choice of services. The primary outcome was 6-month prolonged smoking abstinence at 1 year and was assessed by a follow-up survey among all current smokers regardless of interest in quitting or treatment utilization. A total of 5123 participants were included in the primary analysis. The follow-up survey response rate was 66%. The population-level, 6-month prolonged smoking abstinence rate at 1 year was 13.5% for proactive care compared with 10.9% for usual care (P = .02). Logistic regression mixed model analysis showed a significant effect of the proactive care intervention on 6-month prolonged abstinence (odds ratio [OR], 1.27 [95% CI, 1.03-1.57]). In analyses accounting for nonresponse using likelihood-based not-missing-at-random models, the effect of proactive care on 6-month prolonged abstinence persisted (OR, 1.33 [95% CI, 1.17-1.51]). Proactive, population-based tobacco cessation care using proactive outreach to connect smokers to evidence-based telephone or in-person smoking cessation services is effective for increasing long-term population-level cessation rates. clinicaltrials.gov Identifier: NCT00608426.

Genetic diversity of rice tungro spherical virus in tungro-endemic provinces of the Philippines and Indonesia.

PubMed

Azzam, O; Yambao, M L; Muhsin, M; McNally, K L; Umadhay, K M

2000-01-01

The two adjacent genes of coat protein 1 and 2 of rice tungro spherical virus (RTSV) were amplified from total RNA extracts of serologically indistinguishable field isolates from the Philippines and Indonesia, using reverse transcriptase polymerase chain reaction (RT-PCR). Digestion with HindIII and BstYI restriction endonucleases differentiated the amplified DNA products into eight distinct coat protein genotypes. These genotypes were then used as indicators of virus diversity in the field. Inter- and intra-site diversities were determined over three cropping seasons. At each of the sites surveyed, one or two main genotypes prevailed together with other related minor or mixed genotypes that did not replace the main genotype over the sampling time. The cluster of genotypes found at the Philippines sites was significantly different from the one at the Indonesia sites, suggesting geographic isolation for virus populations. Phylogenetic studies based on the nucleotide sequences of 38 selected isolates confirm the spatial distribution of RTSV virus populations but show that gene flow may occur between populations. Under the present conditions, rice varieties do not seem to exert selective pressure on the virus populations. Based on the selective constraints in the coat protein amino acid sequences and the virus genetic composition per site, a negative selection model followed by random-sampling events due to vector transmissions is proposed to explain the inter-site diversity observed.

Joint modeling and registration of cell populations in cohorts of high-dimensional flow cytometric data.

PubMed

Pyne, Saumyadipta; Lee, Sharon X; Wang, Kui; Irish, Jonathan; Tamayo, Pablo; Nazaire, Marc-Danie; Duong, Tarn; Ng, Shu-Kay; Hafler, David; Levy, Ronald; Nolan, Garry P; Mesirov, Jill; McLachlan, Geoffrey J

2014-01-01

In biomedical applications, an experimenter encounters different potential sources of variation in data such as individual samples, multiple experimental conditions, and multivariate responses of a panel of markers such as from a signaling network. In multiparametric cytometry, which is often used for analyzing patient samples, such issues are critical. While computational methods can identify cell populations in individual samples, without the ability to automatically match them across samples, it is difficult to compare and characterize the populations in typical experiments, such as those responding to various stimulations or distinctive of particular patients or time-points, especially when there are many samples. Joint Clustering and Matching (JCM) is a multi-level framework for simultaneous modeling and registration of populations across a cohort. JCM models every population with a robust multivariate probability distribution. Simultaneously, JCM fits a random-effects model to construct an overall batch template--used for registering populations across samples, and classifying new samples. By tackling systems-level variation, JCM supports practical biomedical applications involving large cohorts. Software for fitting the JCM models have been implemented in an R package EMMIX-JCM, available from http://www.maths.uq.edu.au/~gjm/mix_soft/EMMIX-JCM/.

A National survey of methyl tert-butyl ether and other volatile organic compounds in drinking-water sources: Results of the random source-water survey

USGS Publications Warehouse

Grady, Stephen J.

2002-01-01

Methyl tert-butyl ether (MTBE) was detected in source water used by 8.7 percent of randomly selected community water systems (CWSs) in the United States at concentrations that ranged from 0.2 to 20 micrograms per liter (μg/L). The Random Survey conducted by the U.S. Geological Survey, in cooperation with the Metropolitan Water District of Southern California and the Oregon Health & Science University, was designed to provide an assessment of the frequency of detection, concentration, and distribution of MTBE, three other ether gasoline oxygenates, and 62 other volatile organic compounds (VOCs) in ground- and surface-water sources used for drinking-water supplies. The Random Survey was the first of two components of a national assessment of the quality of source water supplying CWSs sponsored by the American Water Works Association Research Foundation. A total of 954 CWSs were selected for VOC sampling from the population of nearly 47,000 active, self-supplied CWSs in all 50 States, Native American Lands, and Puerto Rico based on a statistical design that stratified on CWS size (population served), type of source water (ground and surface water), and geographic distribution (State).At a reporting level of 0.2 μg/L, VOCs were detected in 27 percent of source-water samples collected from May 3, 1999 through October 23, 2000. Chloroform (in 13 percent of samples) was the most frequently detected of 42 VOCs present in the source-water samples, followed by MTBE. VOC concentrations were generally less than 10 μg/L 95 percent of the 530 detections and 63 percent were less than 1.0 μg/L. Concentrations of 1,1-dichloroethene, tetrachloroethene, trichloroethene, vinyl chloride, and total trihalomethanes (TTHMs), however, exceeded drinking-water regulations in eight samples.Detections of most VOCs were more frequent in surface-water sources than in ground-water sources, with gasoline compounds collectively and MTBE individually detected significantly more often in surface water. Use of personal and commercial motorized watercraft on surface-water bodies that are drinking-water sources is probably the reason for the elevated detections of gasoline contaminants relative to ground water. MTBE detections demonstrated a seasonal pattern with more frequent detections in surface water in summer months, which is consistent with seasonal watercraft use.The detection frequency of most VOCs was significantly related to urban land use and population density. Detections of any VOC, non-trihalo-methane compounds, gasoline compounds collectively, the specific gasoline compounds benzene, toluene, ethylbenzene, and xylenes (BTEX), MTBE, solvents, and refrigerants were significantly greater in areas with more than 60 percent urban land use and (or) population density greater than 1,000 people per square mile than in source waters from less urbanized or lower population-density areas. MTBE detections were five times more frequent in source waters from areas with high MTBE use than in source waters from low or no MTBE use, but, unlike other gasoline compounds, MTBE detections were not significantly related to the density of gasoline storage tanks near drinking-water sources.

Implications of sampling design and sample size for national carbon accounting systems.

PubMed

Köhl, Michael; Lister, Andrew; Scott, Charles T; Baldauf, Thomas; Plugge, Daniel

2011-11-08

Countries willing to adopt a REDD regime need to establish a national Measurement, Reporting and Verification (MRV) system that provides information on forest carbon stocks and carbon stock changes. Due to the extensive areas covered by forests the information is generally obtained by sample based surveys. Most operational sampling approaches utilize a combination of earth-observation data and in-situ field assessments as data sources. We compared the cost-efficiency of four different sampling design alternatives (simple random sampling, regression estimators, stratified sampling, 2-phase sampling with regression estimators) that have been proposed in the scope of REDD. Three of the design alternatives provide for a combination of in-situ and earth-observation data. Under different settings of remote sensing coverage, cost per field plot, cost of remote sensing imagery, correlation between attributes quantified in remote sensing and field data, as well as population variability and the percent standard error over total survey cost was calculated. The cost-efficiency of forest carbon stock assessments is driven by the sampling design chosen. Our results indicate that the cost of remote sensing imagery is decisive for the cost-efficiency of a sampling design. The variability of the sample population impairs cost-efficiency, but does not reverse the pattern of cost-efficiency of the individual design alternatives. Our results clearly indicate that it is important to consider cost-efficiency in the development of forest carbon stock assessments and the selection of remote sensing techniques. The development of MRV-systems for REDD need to be based on a sound optimization process that compares different data sources and sampling designs with respect to their cost-efficiency. This helps to reduce the uncertainties related with the quantification of carbon stocks and to increase the financial benefits from adopting a REDD regime.

Guided self-help on the Internet for Turkish migrants with depression: the design of a randomized controlled trial.

PubMed

Unlü, Burçin; Riper, Heleen; van Straten, Annemieke; Cuijpers, Pim

2010-11-04

The Turkish population living in The Netherlands has a high prevalence of psychological complaints and has a high threshold for seeking professional help for these problems. Seeking help through the Internet can overcome these barriers. This project aims to evaluate the effectiveness of a guided self-help problem-solving intervention for depressed Turkish migrants that is culturally adapted and web-based. This study is a randomized controlled trial with two arms: an experimental condition group and a wait list control group. The experimental condition obtains direct access to the guided web-based self-help intervention, which is based on Problem Solving Treatment (PST) and takes 6 weeks to complete. Turkish adults with mild to moderate depressive symptoms will be recruited from the general population and the participants can choose between a Turkish and a Dutch version. The primary outcome measure is the reduction of depressive symptoms, the secondary outcome measures are somatic symptoms, anxiety, acculturation, quality of life and satisfaction. Participants are assessed at baseline, post-test (6 weeks), and 4 months after baseline. Analysis will be conducted on the intention-to-treat sample. This study evaluates the effectiveness of a guided problem-solving intervention for Turkish adults living in The Netherlands that is culturally adapted and web-based. Nederlands Trial Register: NTR2303.

Adaptive Peer Sampling with Newscast

NASA Astrophysics Data System (ADS)

Tölgyesi, Norbert; Jelasity, Márk

The peer sampling service is a middleware service that provides random samples from a large decentralized network to support gossip-based applications such as multicast, data aggregation and overlay topology management. Lightweight gossip-based implementations of the peer sampling service have been shown to provide good quality random sampling while also being extremely robust to many failure scenarios, including node churn and catastrophic failure. We identify two problems with these approaches. The first problem is related to message drop failures: if a node experiences a higher-than-average message drop rate then the probability of sampling this node in the network will decrease. The second problem is that the application layer at different nodes might request random samples at very different rates which can result in very poor random sampling especially at nodes with high request rates. We propose solutions for both problems. We focus on Newscast, a robust implementation of the peer sampling service. Our solution is based on simple extensions of the protocol and an adaptive self-control mechanism for its parameters, namely—without involving failure detectors—nodes passively monitor local protocol events using them as feedback for a local control loop for self-tuning the protocol parameters. The proposed solution is evaluated by simulation experiments.

The Prevalence of Amblyopia and Its Determinants in a Population-based Study.

PubMed

Faghihi, Mohammad; Hashemi, Hassan; Nabovati, Payam; Saatchi, Mohammad; Yekta, Abbasali; Rafati, Shokoofeh; Ostadimoghaddam, Hadi; Khabazkhoob, Mehdi

2017-12-01

To determine the prevalence of amblyopia and its determinants in a population-based study in Mashhad County, Iran. This cross-sectional, population-based study was conducted on the population of Mashhad County aged >1 year using randomized stratified cluster sampling. Examinations were performed after selection of the participants and their free transportation to the sampling site. The examinations included the measurement of uncorrected and corrected visual acuity, cycloplegic and non-cycloplegic refraction, cover testing, slit-lamp biomicroscopy, and ophthalmoscopy. In this study, amblyopia was defined as best corrected visual acuity (BCVA) of 20/30 or less or 2-line interocular optotype acuity differences with no pathology. After considering the exclusion criteria, the data of 2739 individuals, 65.6% of whom were women, were analyzed. The mean age of the participants was 29.5±17.5 years. The prevalence of amblyopia was 4.6% (95% CI: 3.77%-5.43%) in the total population. The lowest prevalence was 2.24% in the age group 5-15 years (95% CI: 0.99%-3.48%) and the highest prevalence was 7.14% in the age group 55-65 years (95% CI: 2.64%-11.56%). Anisometropic amblyopia was observed in 45.24% of the amblyopic participants. Isometropic, mixed (strabismic/anisometropic), and strabismic amblyopia were other common causes of amblyopia, with a prevalence of 24.6%, 16.67%, and 13.49% in amblyopic patients, respectively. The odds ratio (OR) of having amblyopia for each 1-year increase in age was 1.02 (95% CI: 1.01-1.03). Amblyopia was less common in people with better socioeconomic status. This study showed the prevalence of amblyopia in all age groups in a population-based study for the first time. The findings of this study regarding the relatively high prevalence of amblyopia in the older population and its lower prevalence in young people indicate attention to amblyopia in recent years.

Cancer Screening Practices among Physicians Serving Chinese Immigrants

PubMed Central

Aragones, Abraham; Trinh-Shevrin, Chau; Gany, Francesca

2012-01-01

Chinese immigrants in the United States are broadly affected by cancer health disparities. We examined the cancer screening attitudes and practices of physicians serving Chinese immigrants in the New York City (NYC) area by mailing a cancer screening survey, based on current guidelines, to a random sample of physicians serving this population. Fifty three physicians (44%) completed the survey. Seventy-two percent reported following the guidelines for breast cancer, 35% for cervical cancer screening, and 45% for all colorectal cancer screening tests. Sixty-eight percent of physicians were satisfied with their current rates of cancer screening with their Chinese immigrant patient population. Physicians serving the Chinese community in NYC follow cancer screening guidelines inadequately. Cancer screening rates in this population could likely be increased by interventions that target physicians and improve awareness of guidelines and recommended best practices. PMID:19202247

Statistical considerations for grain-size analyses of tills

USGS Publications Warehouse

Jacobs, A.M.

1971-01-01

Relative percentages of sand, silt, and clay from samples of the same till unit are not identical because of different lithologies in the source areas, sorting in transport, random variation, and experimental error. Random variation and experimental error can be isolated from the other two as follows. For each particle-size class of each till unit, a standard population is determined by using a normally distributed, representative group of data. New measurements are compared with the standard population and, if they compare satisfactorily, the experimental error is not significant and random variation is within the expected range for the population. The outcome of the comparison depends on numerical criteria derived from a graphical method rather than on a more commonly used one-way analysis of variance with two treatments. If the number of samples and the standard deviation of the standard population are substituted in a t-test equation, a family of hyperbolas is generated, each of which corresponds to a specific number of subsamples taken from each new sample. The axes of the graphs of the hyperbolas are the standard deviation of new measurements (horizontal axis) and the difference between the means of the new measurements and the standard population (vertical axis). The area between the two branches of each hyperbola corresponds to a satisfactory comparison between the new measurements and the standard population. Measurements from a new sample can be tested by plotting their standard deviation vs. difference in means on axes containing a hyperbola corresponding to the specific number of subsamples used. If the point lies between the branches of the hyperbola, the measurements are considered reliable. But if the point lies outside this region, the measurements are repeated. Because the critical segment of the hyperbola is approximately a straight line parallel to the horizontal axis, the test is simplified to a comparison between the means of the standard population and the means of the subsample. The minimum number of subsamples required to prove significant variation between samples caused by different lithologies in the source areas and sorting in transport can be determined directly from the graphical method. The minimum number of subsamples required is the maximum number to be run for economy of effort. ?? 1971 Plenum Publishing Corporation.

Prevalence, clinical features and risk assessment of pre-diabetes in Spain: the prospective Mollerussa cohort study

PubMed Central

Vilanova, María Belén; Falguera, Mireia; Marsal, Josep Ramon; Rubinat, Esther; Alcubierre, Núria; Catelblanco, Esmeralda; Granado-Casas, Minerva; Miró, Neus; Molló, Àngels; Mata-Cases, Manel; Franch-Nadal, Josep; Mauricio, Didac

2017-01-01

Purpose The Mollerussa prospective cohort was created to study pre-diabetes in a population-based sample from the primary care setting in the semirural area of Pla d’Urgell in Catalonia (Spain). The aims of the study were to assess the prevalence of pre-diabetes in our population, the likelihood to develop overt diabetes over time and to identify risk factors associated with the progression of the condition. Participants The cohort includes 594 subjects randomly selected between March 2011 and July 2014 from our primary care population, who were older than 25 years, consented to participate and did not have a recorded diagnosis of diabetes. Findings to date At baseline, we performed a clinical interview to collect demographic, clinical and lifestyle (including a nutritional survey) characteristics; carotid ultrasound imaging to assess subclinical cardiovascular disease was also performed, and a blood sample was collected, with an overall <5% rate of missing data. An additional blood draw was performed 12 months after initial recruitment to reassess laboratory results in patients initially identified as having pre-diabetes, with an 89.6% retention rate. Several studies investigating various hypotheses are currently ongoing. Future plans All subjects recruited during the cohort creation will be followed long-term through annual extraction of data from health records stored in the electronic Clinical station in Primary Care database. The Mollerussa cohort will thus be a sound population-based sample for multiple future research projects to generate insights into the epidemiology and natural history of pre-diabetes in Spain. PMID:28606902

Designing a smoking cessation intervention for the unique needs of homeless persons: a community-based randomized clinical trial.

PubMed

Goldade, Kate; Whembolua, Guy-Lucien; Thomas, Janet; Eischen, Sara; Guo, Hongfei; Connett, John; Des Jarlais, Don; Resnicow, Ken; Gelberg, Lillian; Owen, Greg; Grant, Jon; Ahluwalia, Jasjit S; Okuyemi, Kolawole S

2011-12-01

Although smoking prevalence remains strikingly high in homeless populations (~70% and three times the US national average), smoking cessation studies usually exclude homeless persons. Novel evidence-based interventions are needed for this high-risk subpopulation of smokers. To describe the aims and design of a first-ever smoking cessation clinical trial in the homeless population. The study was a two-group randomized community-based trial that enrolled participants (n = 430) residing across eight homeless shelters and transitional housing units in Minnesota. The study objective was to test the efficacy of motivational interviewing (MI) for enhancing adherence to nicotine replacement therapy (NRT; nicotine patch) and smoking cessation outcomes. Participants were randomized to one of the two groups: active (8 weeks of NRT + 6 sessions of MI) or control (NRT + standard care). Participants attended six in-person assessment sessions and eight retention visits at a location of their choice over 6 months. Nicotine patch in 2-week doses was administered at four visits over the first 8 weeks of the 26-week trial. The primary outcome was cotinine-verified 7-day point-prevalence abstinence at 6 months. Secondary outcomes included adherence to nicotine patch assessed through direct observation and patch counts. Other outcomes included the mediating and/or moderating effects of comorbid psychiatric and substance abuse disorders. Lessons learned from the community-based cessation randomized trial for improving recruitment and retention in a mobile and vulnerable population included: (1) the importance of engaging the perspectives of shelter leadership by forming and convening a Community Advisory Board; (2) locating the study at the shelters for more visibility and easier access for participants; (3) minimizing exclusion criteria to allow enrollment of participants with stable psychiatric comorbid conditions; (4) delaying the baseline visit from the eligibility visit by a week to protect against attrition; and (5) regular and persistent calls to remind participants of upcoming appointments using cell phones and shelter-specific channels of communication. The study's limitations include generalizability due to the sample drawn from a single Midwestern city in the United States. Since inclusion criteria encompassed willingness to use NRT patch, all participants were motivated and were ready to quit smoking at the time of enrollment in the study. Findings from the self-select group will be generalizable only to those motivated and ready to quit smoking. High incentives may limit the degree to which the intervention is replicable. Lessons learned reflect the need to engage communities in the design and implementation of community-based clinical trials with vulnerable populations.

Prevalence and correlations of lower urinary tract symptoms, erectile dysfunction and incontinence in men from a multiethnic Asian population: Results of a regional population-based survey and comparison with industrialized nations.

PubMed

Mariappan, Paramananthan; Chong, Wooi Loong

2006-12-01

To determine, in a population-based survey, the prevalence of lower urinary tract symptoms (LUTS), erectile dysfunction (ED) and incontinence in community-dwelling men in multiethnic Malaysia, as currently available Western demographic data might not be applicable in the Asian population. A cross-sectional population-based survey was carried out in the State of Penang, Malaysia, with a target population of men aged > or = 40 years. Using a multistage study design, random systematic sampling was used to represent the target population, who were weighted based on ethnicity and rural-urban ratios so as to represent the general population distribution. Trained field-workers conducted direct interviews and administered the American Urological Association Symptom Index (AUA-SI), the International Index of Erectile Function (IIEF-5) questionnaire and questions on incontinence based on the International Continence Society 2002 definition. In all, 418 men aged > or = 40 years were interviewed, of whom 353 completed the AUA-SI questionnaire (84.5% response rate). The prevalence of mild, moderate and severe LUTS was 80.6%, 6% and 0.3%, respectively. The prevalent symptoms were frequency and nocturia. There was moderate and severe ED in 45.9% of men, whereas incontinence was reported by 8.2%. The AUA-SI correlated strongly with age (R = 0.291, P < 0.001), IIEF-5 (R = - 0.265, P < 0.001) and diabetes mellitus. The prevalence and severity of LUTS, ED and incontinence increased with age in this multiethnic Asian population, in which ED correlated strongly with LUTS. Compared to the Western population, the prevalence of LUTS was significantly lower, while the prevalence of ED and incontinence were comparable.

Effects of a home-based physical rehabilitation program on physical disability after hip fracture: a randomized controlled trial.

PubMed

Edgren, Johanna; Salpakoski, Anu; Sihvonen, Sanna E; Portegijs, Erja; Kallinen, Mauri; Arkela, Marja; Jäntti, Pirkko; Vanhatalo, Jukka; Pekkonen, Mika; Rantanen, Taina; Heinonen, Ari; Sipilä, Sarianna

2015-04-01

Fewer than half of the patients with hip fracture will regain the prefracture level of physical functioning. This secondary analysis of a randomized controlled trial investigated the effects of a multicomponent home-based rehabilitation program (ProMo) on physical disability after hip fracture. Randomized, controlled, parallel-group trial. Rehabilitation in participants' homes; measurements in university-based laboratory and local hospital. Population-based clinical sample of community-dwelling people older than 60 years (n = 81) operated for hip fracture were randomized into intervention and control groups. The year-long intervention aimed at restoring mobility. It included evaluation and modification of environmental hazards, guidance for safe walking, pain management, home exercise, physical activity counseling, and standard care. Physical disability was assessed by a questionnaire at baseline, and 3, 6, and 12 months thereafter. Sum scores were computed for basic (ADLs) and instrumental activities of daily living (IADLs). A higher score indicated more difficulty. GEE models were constructed to analyze the effect of the intervention. In the intention-to-treat analysis, no intervention effect was observed for sum scores. For the single disability items, borderline significant positive effects were observed for preparing food and handling medication (interaction P = .061 and P = .061, respectively). In the per-protocol analysis, the mean differences between groups were -0.4 points (SE 0.5), -1.7 (0.7), and -1.2 (0.7) at 3, 6, and 12 months for ADLs and -1.0 (1.2), -3.2 (1.5), and -2.5 (1.4) for IADLs, correspondingly. The current analyses suggest that home-based rehabilitation may reduce disability among older people after hip fracture. The present results need to be confirmed in a study with larger sample size. Potentially a more task-oriented rehabilitation approach might gain more benefits. Current Controlled Trials (ISRCTN53680197). Copyright © 2015 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.

Crime Victimization in Adults With Severe Mental Illness

PubMed Central

Teplin, Linda A.; McClelland, Gary M.; Abram, Karen M.; Weiner, Dana A.

2006-01-01

Context Since deinstitutionalization, most persons with severe mental illness (SMI) now live in the community, where they are at great risk for crime victimization. Objectives To determine the prevalence and incidence of crime victimization among persons with SMI by sex, race/ethnicity, and age, and to compare rates with general population data (the National Crime Victimization Survey), controlling for income and demographic differences between the samples. Design Epidemiologic study of persons in treatment. Independent master’s-level clinical research interviewers administered the National Crime Victimization Survey to randomly selected patients sampled from 16 randomly selected mental health agencies. Setting Sixteen agencies providing outpatient, day, and residential treatment to persons with SMI in Chicago, Ill. Participants Randomly selected, stratified sample of 936 patients aged 18 or older (483 men, 453 women) who were African American (n = 329), non-Hispanic white (n = 321), Hispanic (n = 270), or other race/ethnicity (n = 22). The comparison group comprised 32449 participants in the National Crime Victimization Survey. Main Outcome Measure National Crime Victimization Survey, developed by the Bureau of Justice Statistics. Results More than one quarter of persons with SMI had been victims of a violent crime in the past year, a rate more than 11 times higher than the general population rates even after controlling for demographic differences between the 2 samples (P<.001). The annual incidence of violent crime in the SMI sample (168.2 incidents per 1000 persons) is more than 4 times higher than the general population rates (39.9 incidents per 1000 persons) (P<.001). Depending on the type of violent crime (rape/sexual assault, robbery, assault, and their subcategories), prevalence was 6 to 23 times greater among persons with SMI than among the general population. Conclusions Crime victimization is a major public health problem among persons with SMI who are treated in the community. We recommend directions for future research, propose modifications in public policy, and suggest how the mental health system can respond to reduce victimization and its consequences. PMID:16061769

Crime victimization in adults with severe mental illness: comparison with the National Crime Victimization Survey.

PubMed

Teplin, Linda A; McClelland, Gary M; Abram, Karen M; Weiner, Dana A

2005-08-01

Since deinstitutionalization, most persons with severe mental illness (SMI) now live in the community, where they are at great risk for crime victimization. To determine the prevalence and incidence of crime victimization among persons with SMI by sex, race/ethnicity, and age, and to compare rates with general population data (the National Crime Victimization Survey), controlling for income and demographic differences between the samples. Epidemiologic study of persons in treatment. Independent master's-level clinical research interviewers administered the National Crime Victimization Survey to randomly selected patients sampled from 16 randomly selected mental health agencies. Sixteen agencies providing outpatient, day, and residential treatment to persons with SMI in Chicago, Ill. Randomly selected, stratified sample of 936 patients aged 18 or older (483 men, 453 women) who were African American (n = 329), non-Hispanic white (n = 321), Hispanic (n = 270), or other race/ethnicity (n = 22). The comparison group comprised 32 449 participants in the National Crime Victimization Survey. National Crime Victimization Survey, developed by the Bureau of Justice Statistics. More than one quarter of persons with SMI had been victims of a violent crime in the past year, a rate more than 11 times higher than the general population rates even after controlling for demographic differences between the 2 samples (P<.001). The annual incidence of violent crime in the SMI sample (168.2 incidents per 1000 persons) is more than 4 times higher than the general population rates (39.9 incidents per 1000 persons) (P<.001). Depending on the type of violent crime (rape/sexual assault, robbery, assault, and their subcategories), prevalence was 6 to 23 times greater among persons with SMI than among the general population. Crime victimization is a major public health problem among persons with SMI who are treated in the community. We recommend directions for future research, propose modifications in public policy, and suggest how the mental health system can respond to reduce victimization and its consequences.

Using Panel Vendors for Recruitment Into a Web-Based Family Prevention Program: Methodological Considerations.

PubMed

Wang-Schweig, Meme; Miller, Brenda A; Buller, David B; Byrnes, Hilary F; Bourdeau, Beth; Rogers, Veronica

2017-01-01

Use of online panel vendors in research has grown over the past decade. Panel vendors are organizations that recruit participants into a panel to take part in web-based surveys and match panelists to a target audience for data collection. We used two panel vendors to recruit families ( N = 411) with a 16- to 17-year-old teen to participate in a randomized control trial (RCT) of an online family-based program to prevent underage drinking and risky sexual behaviors. Our article addresses the following research questions: (1) How well do panel vendors provide a sample of families who meet our inclusion criteria to participate in a RCT? (2) How well do panel vendors provide a sample of families who reflect the characteristics of the general population? and (3) Does the choice of vendor influence the characteristics of families that we engage in research? Despite the screening techniques used by the panel vendors to identify families who met our inclusion criteria, 23.8% were found ineligible when research staff verified their eligibility by direct telephone contact. Compared to the general U.S. population, our sample had more Whites and more families with higher education levels. Finally, across the two panel vendors, there were no significant differences in the characteristics of families, except for mean age. The online environment provides opportunities for new methods to recruit participants in research studies. However, innovative recruitment methods need careful study to ensure the quality of their samples.

Two-year changes in refractive error and related biometric factors in an adult Chinese population.

PubMed

He, Mingguang; Kong, Xiangbin; Chen, Qianyun; Zeng, Yangfa; Huang, Yuanzhou; Zhang, Jian; Morgan, Ian G; Meltzer, Mirjam E; Jin, Ling; Congdon, Nathan

2014-08-01

This article provides, to our knowledge, the first longitudinal population-based data on refractive error (RE) in Chinese persons. To study cohort effects and changes associated with aging in REs among Chinese adults. A 2-year, longitudinal population-based cohort study was conducted in southern China. Participants, identified using cluster random sampling, included residents of Yuexiu District, Guangzhou, China, aged 35 years or older who had undergone no previous eye surgery. Participants underwent noncycloplegic automated refraction and keratometry in December 2008 and December 2010; in a random 50% sample of the participants, anterior segment ocular coherence tomography measurement of lens thickness, as well as measurement of axial length and anterior chamber depth by partial coherence laser interferometry, were performed. Two-year change in spherical equivalent refraction (RE), lens thickness, axial length, and anterior chamber depth in the right eye. A total of 745 individuals underwent biometric testing in both 2008 and 2010 (2008 mean [SD] age, 52.2 [11.5] years; 53.7% women). Mean RE showed a 2-year hyperopic shift from -0.44 (2.21) to -0.31 (2.26) diopters (D) (difference, +0.13; 95% CI, 0.11 to 0.16). A consistent 2-year hyperopic shift of 0.09 to 0.22 D was observed among participants aged 35 to 64 years when stratifying by decade, suggesting that a substantial change in RE with aging may occur during this 30-year period. Cross-sectionally, RE increased only in the cohort younger than 50 years (0.11 D/y; 95% CI, 0.06 to 0.16). In the cross-sectional data, axial length decreased at -0.06 mm/y (95% CI, -0.09 to -0.04), although the 2-year change in axial length was positive and thus could not explain the cross-sectional difference. These latter results suggest a cohort effect, with greater myopia developing among younger persons. This first Chinese population-based longitudinal study of RE provides evidence for both important longitudinal aging changes and cohort effects, most notably greater myopia prevalence among younger persons.

Can work ability explain the social gradient in sickness absence: a study of a general population in Sweden.

PubMed

Löve, Jesper; Holmgren, Kristina; Torén, Kjell; Hensing, Gunnel

2012-03-07

Understanding the reasons for the social gradient in sickness absence might provide an opportunity to reduce the general rates of sickness absence. The complete explanation for this social gradient still remains unclear and there is a need for studies using randomized working population samples. The main aim of the present study was to investigate if self-reported work ability could explain the association between low socioeconomic position and belonging to a sample of new cases of sick-listed employees. The two study samples consisted of a randomized working population (n = 2,763) and a sample of new cases of sick-listed employees (n = 3,044), 19-64 years old. Both samples were drawn from the same randomized general population. Socioeconomic status was measured with occupational position and physical and mental work ability was measured with two items extracted from the work ability index. There was an association between lower socioeconomic status and belonging to the sick-listed sample among both women and men. In men the crude Odds ratios increased for each downwards step in socioeconomic status, OR 1.32 (95% CI 0.98-1.78), OR 1.53 (1.05-2.24), OR 2.80 (2.11-3.72), and OR 2.98 (2.27-3.90). Among women this gradient was not as pronounced. Physical work ability constituted the strongest explanatory factor explaining the total association between socioeconomic status and being sick-listed in women. However, among men, the association between skilled non-manual, OR 2.07 (1.54-2.78), and non-skilled manual, OR 2.03 (1.53-2.71) positions in relation to being sick-listed remained. The explanatory effect of mental work ability was small. Surprisingly, even in the sick-listed sample most respondents had high mental and physical work ability. These results suggest that physical work ability may be an important key in explaining the social gradient in sickness absence, particularly in women. Hence, it is possible that the factors associated with the social gradient in sickness absence may differ, to some extent, between women and men.

Assessing tiger population dynamics using photographic capture-recapture sampling

USGS Publications Warehouse

Karanth, K.U.; Nichols, J.D.; Kumar, N.S.; Hines, J.E.

2006-01-01

Although wide-ranging, elusive, large carnivore species, such as the tiger, are of scientific and conservation interest, rigorous inferences about their population dynamics are scarce because of methodological problems of sampling populations at the required spatial and temporal scales. We report the application of a rigorous, noninvasive method for assessing tiger population dynamics to test model-based predictions about population viability. We obtained photographic capture histories for 74 individual tigers during a nine-year study involving 5725 trap-nights of effort. These data were modeled under a likelihood-based, ?robust design? capture?recapture analytic framework. We explicitly modeled and estimated ecological parameters such as time-specific abundance, density, survival, recruitment, temporary emigration, and transience, using models that incorporated effects of factors such as individual heterogeneity, trap-response, and time on probabilities of photo-capturing tigers. The model estimated a random temporary emigration parameter of =K' =Y' 0.10 ? 0.069 (values are estimated mean ? SE). When scaled to an annual basis, tiger survival rates were estimated at S = 0.77 ? 0.051, and the estimated probability that a newly caught animal was a transient was = 0.18 ? 0.11. During the period when the sampled area was of constant size, the estimated population size Nt varied from 17 ? 1.7 to 31 ? 2.1 tigers, with a geometric mean rate of annual population change estimated as = 1.03 ? 0.020, representing a 3% annual increase. The estimated recruitment of new animals, Bt, varied from 0 ? 3.0 to 14 ? 2.9 tigers. Population density estimates, D, ranged from 7.33 ? 0.8 tigers/100 km2 to 21.73 ? 1.7 tigers/100 km2 during the study. Thus, despite substantial annual losses and temporal variation in recruitment, the tiger density remained at relatively high levels in Nagarahole. Our results are consistent with the hypothesis that protected wild tiger populations can remain healthy despite heavy mortalities because of their inherently high reproductive potential. The ability to model the entire photographic capture history data set and incorporate reduced-parameter models led to estimates of mean annual population change that were sufficiently precise to be useful. This efficient, noninvasive sampling approach can be used to rigorously investigate the population dynamics of tigers and other elusive, rare, wide-ranging animal species in which individuals can be identified from photographs or other means.

Assessing tiger population dynamics using photographic capture-recapture sampling.

PubMed

Karanth, K Ullas; Nichols, James D; Kumar, N Samba; Hines, James E

2006-11-01

Although wide-ranging, elusive, large carnivore species, such as the tiger, are of scientific and conservation interest, rigorous inferences about their population dynamics are scarce because of methodological problems of sampling populations at the required spatial and temporal scales. We report the application of a rigorous, noninvasive method for assessing tiger population dynamics to test model-based predictions about population viability. We obtained photographic capture histories for 74 individual tigers during a nine-year study involving 5725 trap-nights of effort. These data were modeled under a likelihood-based, "robust design" capture-recapture analytic framework. We explicitly modeled and estimated ecological parameters such as time-specific abundance, density, survival, recruitment, temporary emigration, and transience, using models that incorporated effects of factors such as individual heterogeneity, trap-response, and time on probabilities of photo-capturing tigers. The model estimated a random temporary emigration parameter of gamma" = gamma' = 0.10 +/- 0.069 (values are estimated mean +/- SE). When scaled to an annual basis, tiger survival rates were estimated at S = 0.77 +/- 0.051, and the estimated probability that a newly caught animal was a transient was tau = 0.18 +/- 0.11. During the period when the sampled area was of constant size, the estimated population size N(t) varied from 17 +/- 1.7 to 31 +/- 2.1 tigers, with a geometric mean rate of annual population change estimated as lambda = 1.03 +/- 0.020, representing a 3% annual increase. The estimated recruitment of new animals, B(t), varied from 0 +/- 3.0 to 14 +/- 2.9 tigers. Population density estimates, D, ranged from 7.33 +/- 0.8 tigers/100 km2 to 21.73 +/- 1.7 tigers/100 km2 during the study. Thus, despite substantial annual losses and temporal variation in recruitment, the tiger density remained at relatively high levels in Nagarahole. Our results are consistent with the hypothesis that protected wild tiger populations can remain healthy despite heavy mortalities because of their inherently high reproductive potential. The ability to model the entire photographic capture history data set and incorporate reduced-parameter models led to estimates of mean annual population change that were sufficiently precise to be useful. This efficient, noninvasive sampling approach can be used to rigorously investigate the population dynamics of tigers and other elusive, rare, wide-ranging animal species in which individuals can be identified from photographs or other means.

Deterministic multidimensional nonuniform gap sampling.

PubMed

Worley, Bradley; Powers, Robert

2015-12-01

Born from empirical observations in nonuniformly sampled multidimensional NMR data relating to gaps between sampled points, the Poisson-gap sampling method has enjoyed widespread use in biomolecular NMR. While the majority of nonuniform sampling schemes are fully randomly drawn from probability densities that vary over a Nyquist grid, the Poisson-gap scheme employs constrained random deviates to minimize the gaps between sampled grid points. We describe a deterministic gap sampling method, based on the average behavior of Poisson-gap sampling, which performs comparably to its random counterpart with the additional benefit of completely deterministic behavior. We also introduce a general algorithm for multidimensional nonuniform sampling based on a gap equation, and apply it to yield a deterministic sampling scheme that combines burst-mode sampling features with those of Poisson-gap schemes. Finally, we derive a relationship between stochastic gap equations and the expectation value of their sampling probability densities. Copyright © 2015 Elsevier Inc. All rights reserved.

Pattern of relative growth in cockle Anadara antiquata in Ihamahu coastal waters, Central Maluku

NASA Astrophysics Data System (ADS)

Siahainenia, L.; Tuhumury, S. F.; Uneputty, P. A.; Tuhumury, N. C.

2018-03-01

Anadara antiquata is economically important species for fisheries and belong to phylum mollusc which also found in Maluku. However, the density of population begins to decrease recently due to high exploitation by people. The objective of the present study was to analyze relative growth pattern of A. antiquata including size distribution and growth pattern based on shell dimensions. The study was conducted from December 2016 to February 2017 in Ihamahu coastal waters. Data were collected by using purposive random sampling. All the individuals of A. antiquata found were measured the length, width and height by using a vernier caliper to the nearest 0.01mm. Data were analyzed by using SPSS 20 and Microsoft Excel software. The results indicated that the A. antiquata mostly found in seagrass bed with a muddy substrate. The size distribution of shell dimensions was different during sampling. Overall, the length ranged from 15.87 mm to 57.5 mm, the width from 15.50 mm to 48.60 mm and the height was from 9.36 mm to 35.9 mm. The population of A. antiquata consisted of juvenile and mature size. The mature size (> 30 mm) was more dominant in the population. The A. antiquata showed allometric relative growth pattern based on shell dimensions.

Error baseline rates of five sample preparation methods used to characterize RNA virus populations.

PubMed

Kugelman, Jeffrey R; Wiley, Michael R; Nagle, Elyse R; Reyes, Daniel; Pfeffer, Brad P; Kuhn, Jens H; Sanchez-Lockhart, Mariano; Palacios, Gustavo F

2017-01-01

Individual RNA viruses typically occur as populations of genomes that differ slightly from each other due to mutations introduced by the error-prone viral polymerase. Understanding the variability of RNA virus genome populations is critical for understanding virus evolution because individual mutant genomes may gain evolutionary selective advantages and give rise to dominant subpopulations, possibly even leading to the emergence of viruses resistant to medical countermeasures. Reverse transcription of virus genome populations followed by next-generation sequencing is the only available method to characterize variation for RNA viruses. However, both steps may lead to the introduction of artificial mutations, thereby skewing the data. To better understand how such errors are introduced during sample preparation, we determined and compared error baseline rates of five different sample preparation methods by analyzing in vitro transcribed Ebola virus RNA from an artificial plasmid-based system. These methods included: shotgun sequencing from plasmid DNA or in vitro transcribed RNA as a basic "no amplification" method, amplicon sequencing from the plasmid DNA or in vitro transcribed RNA as a "targeted" amplification method, sequence-independent single-primer amplification (SISPA) as a "random" amplification method, rolling circle reverse transcription sequencing (CirSeq) as an advanced "no amplification" method, and Illumina TruSeq RNA Access as a "targeted" enrichment method. The measured error frequencies indicate that RNA Access offers the best tradeoff between sensitivity and sample preparation error (1.4-5) of all compared methods.

Kā-HOLO Project: a protocol for a randomized controlled trial of a native cultural dance program for cardiovascular disease prevention in Native Hawaiians.

PubMed

Kaholokula, Joseph Keawe'aimoku; Look, Mele A; Wills, Thomas A; de Silva, Māpuana; Mabellos, Tricia; Seto, Todd B; Ahn, Hyeong Jun; Sinclair, Ka'imi A; Buchwald, Dedra

2017-04-17

As a major risk factor for cardiovascular and cerebrovascular disease (CVD), hypertension affects 33% of U.S. adults. Relative to other US races and ethnicities, Native Hawaiians have a high prevalence of hypertension and are 3 to 4 times more likely to have CVD. Effective, culturally-relevant interventions are needed to address CVD risk in this population. Investigators of the Kā-HOLO Project developed a study design to test the efficacy of an intervention that uses hula, a traditional Hawaiian dance, to increase physical activity and reduce CVD risk. A 2-arm randomized controlled trial with a wait-list control design will be implemented to test a 6-month intervention based on hula to manage blood pressure and reduce CVD risk in 250 adult Native Hawaiians with diagnosed hypertension. Half of the sample will be randomized to each arm, stratified across multiple study sites. Primary outcomes are reduction in systolic blood pressure and improvement in CVD risk as measured by the Framingham Risk Score. Other psychosocial and sociocultural measures will be included to determine mediators of intervention effects on primary outcomes. Assessments will be conducted at baseline, 3 months, and 6 months for all participants, and at 12 months for intervention participants only. This trial will elucidate the efficacy of a novel hypertension management program designed to reduce CVD risk in an indigenous population by using a cultural dance form as its physical activity component. The results of this culturally-based intervention will have implications for other indigenous populations globally and will offer a sustainable, culturally-relevant means of addressing CVD disparities. ClinicalTrials.gov: NCT02620709 , registration date November 23, 2015.

Methodology of the Singapore Indian Chinese Cohort (SICC) eye study: quantifying ethnic variations in the epidemiology of eye diseases in Asians.

PubMed

Lavanya, Raghavan; Jeganathan, V Swetha E; Zheng, Yingfeng; Raju, Prema; Cheung, Ning; Tai, E Shyong; Wang, Jie Jin; Lamoureux, Ecosse; Mitchell, Paul; Young, Terri L; Cajucom-Uy, Howard; Foster, Paul J; Aung, Tin; Saw, Seang Mei; Wong, Tien Y

2009-01-01

Current knowledge of ethnic variability in the epidemiology of major eye diseases in Asia is limited. This report summarizes the rationale and study design of the Singapore Indian Chinese Cohort (SICC) Eye Study, a population-based study of ethnic South Asian (Indians) and East Asian (Chinese) older adults in Singapore. The SICC examined a population-based cross-sectional sample of 3,300 ethnic Indians and 3,300 ethnic Chinese aged 40-80+ years residing in the South-Western part of Singapore. From two lists of 12,000 names of each ethnic group provided by the Ministry of Home Affairs, age-stratified random sampling was used to select 6,350 names in each group, with a target sample size of 3,300. Invitations were sent to attend a central clinic using letters, telephone calls and home visits. Examination procedures included interviews, measurement of blood pressure, anthropometry, presenting and best-corrected visual acuity, subjective refraction, ocular biometry, Goldmann applanation tonometry, slit-lamp biomicroscopy, optic disc imaging and digital photography of the lens and retina, using a standardized protocol. Selected participants underwent gonioscopic examination, visual field testing, and anterior and posterior segment optical coherence tomography. Blood, tear, and urine samples were collected for biochemical analyses, and stored for genetic and proteomic studies. In conjunction with the Singapore Malay Eye Study, the SICC study will permit an in-depth evaluation of the prevalence, risk factors, and impact of major eye diseases in Chinese, Indians and Malays, three distinct Asian ethnic groups, whose combined numbers represent half the world's population.

A random sampling approach for robust estimation of tissue-to-plasma ratio from extremely sparse data.

PubMed

Chu, Hui-May; Ette, Ene I

2005-09-02

his study was performed to develop a new nonparametric approach for the estimation of robust tissue-to-plasma ratio from extremely sparsely sampled paired data (ie, one sample each from plasma and tissue per subject). Tissue-to-plasma ratio was estimated from paired/unpaired experimental data using independent time points approach, area under the curve (AUC) values calculated with the naïve data averaging approach, and AUC values calculated using sampling based approaches (eg, the pseudoprofile-based bootstrap [PpbB] approach and the random sampling approach [our proposed approach]). The random sampling approach involves the use of a 2-phase algorithm. The convergence of the sampling/resampling approaches was investigated, as well as the robustness of the estimates produced by different approaches. To evaluate the latter, new data sets were generated by introducing outlier(s) into the real data set. One to 2 concentration values were inflated by 10% to 40% from their original values to produce the outliers. Tissue-to-plasma ratios computed using the independent time points approach varied between 0 and 50 across time points. The ratio obtained from AUC values acquired using the naive data averaging approach was not associated with any measure of uncertainty or variability. Calculating the ratio without regard to pairing yielded poorer estimates. The random sampling and pseudoprofile-based bootstrap approaches yielded tissue-to-plasma ratios with uncertainty and variability. However, the random sampling approach, because of the 2-phase nature of its algorithm, yielded more robust estimates and required fewer replications. Therefore, a 2-phase random sampling approach is proposed for the robust estimation of tissue-to-plasma ratio from extremely sparsely sampled data.

Midwives Performance in Early Detection of Growth and Development Irregularities of Children Based on Task Commitment

ERIC Educational Resources Information Center

Utami, Sri; Nursalam; Hargono, Rachmat; Susilaningrum, Rekawati

2016-01-01

The purpose of this study was to analyze the performance of midwives based on the task commitment. This was an observational analytic with cross sectional approach. Multistage random sampling was used to determine the public health center, proportional random sampling to selected participants. The samples were 222 midwives in the public health…

A dental public health approach based on computational mathematics: Monte Carlo simulation of childhood dental decay.

PubMed

Tennant, Marc; Kruger, Estie

2013-02-01

This study developed a Monte Carlo simulation approach to examining the prevalence and incidence of dental decay using Australian children as a test environment. Monte Carlo simulation has been used for a half a century in particle physics (and elsewhere); put simply, it is the probability for various population-level outcomes seeded randomly to drive the production of individual level data. A total of five runs of the simulation model for all 275,000 12-year-olds in Australia were completed based on 2005-2006 data. Measured on average decayed/missing/filled teeth (DMFT) and DMFT of highest 10% of sample (Sic10) the runs did not differ from each other by more than 2% and the outcome was within 5% of the reported sampled population data. The simulations rested on the population probabilities that are known to be strongly linked to dental decay, namely, socio-economic status and Indigenous heritage. Testing the simulated population found DMFT of all cases where DMFT<>0 was 2.3 (n = 128,609) and DMFT for Indigenous cases only was 1.9 (n = 13,749). In the simulation population the Sic25 was 3.3 (n = 68,750). Monte Carlo simulations were created in particle physics as a computational mathematical approach to unknown individual-level effects by resting a simulation on known population-level probabilities. In this study a Monte Carlo simulation approach to childhood dental decay was built, tested and validated. © 2013 FDI World Dental Federation.

Web based health surveys: Using a Two Step Heckman model to examine their potential for population health analysis.

PubMed

Morrissey, Karyn; Kinderman, Peter; Pontin, Eleanor; Tai, Sara; Schwannauer, Mathias

2016-08-01

In June 2011 the BBC Lab UK carried out a web-based survey on the causes of mental distress. The 'Stress Test' was launched on 'All in the Mind' a BBC Radio 4 programme and the test's URL was publicised on radio and TV broadcasts, and made available via BBC web pages and social media. Given the large amount of data created, over 32,800 participants, with corresponding diagnosis, demographic and socioeconomic characteristics; the dataset are potentially an important source of data for population based research on depression and anxiety. However, as respondents self-selected to participate in the online survey, the survey may comprise a non-random sample. It may be only individuals that listen to BBC Radio 4 and/or use their website that participated in the survey. In this instance using the Stress Test data for wider population based research may create sample selection bias. Focusing on the depression component of the Stress Test, this paper presents an easy-to-use method, the Two Step Probit Selection Model, to detect and statistically correct selection bias in the Stress Test. Using a Two Step Probit Selection Model; this paper did not find a statistically significant selection on unobserved factors for participants of the Stress Test. That is, survey participants who accessed and completed an online survey are not systematically different from non-participants on the variables of substantive interest. Copyright © 2016 Elsevier Ltd. All rights reserved.

Household-based ceramic water filters for the prevention of diarrhea: a randomized, controlled trial of a pilot program in Colombia.

PubMed

Clasen, Thomas; Garcia Parra, Gloria; Boisson, Sophie; Collin, Simon

2005-10-01

Household water treatment is increasingly recognized as an effective means of reducing the burden of diarrheal disease among low-income populations without access to safe water. Oxfam GB undertook a pilot project to explore the use of household-based ceramic water filters in three remote communities in Colombia. In a randomized, controlled trial over a period of six months, the filters were associated with a 75.3% reduction in arithmetic mean thermotolerant coliforms (TTCs) (P < 0.0001). A total of 47.7% and 24.2% of the samples from the intervention group had no detectible TTCs/100 mL or conformed to World Health Organization limits for low risk (1-10 TTCs/100 mL), respectively, compared with 0.9% and 7.3% for control group samples. Overall, prevalence of diarrhea was 60% less among households using filters than among control households (odds ratio = 0.40, 95% confidence interval = 0.25, 0.63, P < 0.0001). However, the microbiologic performance and protective effect of the filters was not uniform throughout the study communities, suggesting the need to consider the circumstances of the particular setting before implementing this intervention.

Diet quality of a population sample from coastal north-east Spain evaluated by a Mediterranean adaptation of the diet quality index (DQI).

PubMed

Bondia-Pons, Isabel; Mayneris-Perxachs, Jordi; Serra-Majem, Lluís; Castellote, Ana I; Mariné, Abel; López-Sabater, M Carmen

2010-01-01

To assess the adherence to the Mediterranean dietary pattern in the population from a coastal region from north-east Spain and its relationship to diseases, applying the Mediterranean Diet Quality Index (M-DQI) validated by the use of several biomarkers. Cross-sectional nutrition survey. Population-based random sample derived from the Catalan Nutrition Survey. A total of 621 healthy adults. The Catalan representative sample presented a mean M-DQI score of 6.6 (sd 2.3, median 7, range 0-14). The percentage of adherence to the Mediterranean diet was 53 %; 10 % of subjects showed high adherence to the Mediterranean diet, while only 2 % were categorized as poorest adherence. The plasma fatty acid profile of the Catalan sample progressed with perfect regularity throughout the index ranges. Both EPA and DHA presented a significant correlation to the M-DQI (r = -0.410 for EPA and -0.360 for DHA). A significant increase in palmitic, oleic and alpha-linolenic acids and a significant decrease in stearic, linoleic and arachidonic acids content were also observed. The mean values for the M-DQI according to the clinical characteristics of the Catalan sample were also calculated. The M-DQI has been demonstrated a suitable tool for assessment of an individual's nutritional status according to the Mediterranean dietary pattern and for clinical purposes. Although the current diet followed in Catalonia seems to agree with the main characteristics of the Mediterranean diet, the promotion of the Mediterranean pattern should be reinforced in the Catalan population, especially among young people.

Long‐term trends in fall age ratios of black brant

USGS Publications Warehouse

Ward, David H.; Amundson, Courtney L.; Stehn, Robert A.; Dau, Christian P.

2018-01-01

Accurate estimates of the age composition of populations can inform past reproductive success and future population trajectories. We examined fall age ratios (juveniles:total birds) of black brant (Branta bernicla nigricans; brant) staging at Izembek National Wildlife Refuge near the tip of the Alaska Peninsula, southwest Alaska, USA, 1963 to 2015. We also investigated variation in fall age ratios associated with sampling location, an index of flock size, survey effort, day of season, observer, survey platform (boat‐ or land‐based) and tide stage. We analyzed data using logistic regression models implemented in a Bayesian framework. Mean predicted fall age ratio controlling for survey effort, day of year, and temporal and spatial variation was 0.24 (95% CL = 0.23, 0.25). Overall trend in age ratios was −0.6% per year (95% CL = −1.3%, 0.2%), resulting in an approximate 26% decline in the proportion of juveniles over the study period. We found evidence for variation across a range of variables implying that juveniles are not randomly distributed in space and time within Izembek Lagoon. Age ratios varied by location within the study area and were highly variable among years. They decreased with the number of birds aged (an index of flock size) and increased throughout September before leveling off in early October and declining in late October. Age ratios were similar among tide stages and observers and were lower during boat‐based (offshore) than land‐based (nearshore) surveys. Our results indicate surveys should be conducted annually during early to mid‐October to ensure the entire population is present and available for sampling, and throughout Izembek Lagoon to account for spatiotemporal variation in age ratios. Sampling should include a wide range of flock sizes representative of their distribution and occur in flocks located near and off shore. Further research evaluating the cause of declining age ratios in the fall population is necessary to inform management and predict long‐term population dynamics of brant.

Entrepreneurial Intentions of Agricultural Students: Levels and Determinants

ERIC Educational Resources Information Center

Pouratashi, Mahtab

2015-01-01

Purpose: This paper examined levels and determinants of entrepreneurial intentions amongst agricultural students. Methodology: The statistical population comprised students in colleges of agriculture at University of Tehran. By use of a random sampling method, a sample of 120 students participated in the study. The instrument for data collection…

Academic Self-Efficacy Perceptions of Teacher Candidates

ERIC Educational Resources Information Center

Yesilyurt, Etem

2013-01-01

This study aims determining academic self-efficacy perception of teacher candidates. It is survey model. Population of the study consists of teacher candidates in 2010-2011 academic years at Ahmet Kelesoglu Education Faculty of Education Formation of Selcuk University. A simple random sample was selected as sampling method and the study was…

Optimal spatial sampling techniques for ground truth data in microwave remote sensing of soil moisture

NASA Technical Reports Server (NTRS)

Rao, R. G. S.; Ulaby, F. T.

1977-01-01

The paper examines optimal sampling techniques for obtaining accurate spatial averages of soil moisture, at various depths and for cell sizes in the range 2.5-40 acres, with a minimum number of samples. Both simple random sampling and stratified sampling procedures are used to reach a set of recommended sample sizes for each depth and for each cell size. Major conclusions from statistical sampling test results are that (1) the number of samples required decreases with increasing depth; (2) when the total number of samples cannot be prespecified or the moisture in only one single layer is of interest, then a simple random sample procedure should be used which is based on the observed mean and SD for data from a single field; (3) when the total number of samples can be prespecified and the objective is to measure the soil moisture profile with depth, then stratified random sampling based on optimal allocation should be used; and (4) decreasing the sensor resolution cell size leads to fairly large decreases in samples sizes with stratified sampling procedures, whereas only a moderate decrease is obtained in simple random sampling procedures.

HABITAT ASSESSMENT USING A RANDOM PROBABILITY BASED SAMPLING DESIGN: ESCAMBIA RIVER DELTA, FLORIDA

EPA Science Inventory

Smith, Lisa M., Darrin D. Dantin and Steve Jordan. In press. Habitat Assessment Using a Random Probability Based Sampling Design: Escambia River Delta, Florida (Abstract). To be presented at the SWS/GERS Fall Joint Society Meeting: Communication and Collaboration: Coastal Systems...

Development of a sampling strategy and sample size calculation to estimate the distribution of mammographic breast density in Korean women.

PubMed

Jun, Jae Kwan; Kim, Mi Jin; Choi, Kui Son; Suh, Mina; Jung, Kyu-Won

2012-01-01

Mammographic breast density is a known risk factor for breast cancer. To conduct a survey to estimate the distribution of mammographic breast density in Korean women, appropriate sampling strategies for representative and efficient sampling design were evaluated through simulation. Using the target population from the National Cancer Screening Programme (NCSP) for breast cancer in 2009, we verified the distribution estimate by repeating the simulation 1,000 times using stratified random sampling to investigate the distribution of breast density of 1,340,362 women. According to the simulation results, using a sampling design stratifying the nation into three groups (metropolitan, urban, and rural), with a total sample size of 4,000, we estimated the distribution of breast density in Korean women at a level of 0.01% tolerance. Based on the results of our study, a nationwide survey for estimating the distribution of mammographic breast density among Korean women can be conducted efficiently.

Examining iPod Use by Texas Agricultural Science and Technology Teachers

ERIC Educational Resources Information Center

Murphrey, Theresa Pesl; Miller, Kimberly A.; Roberts, T. Grady

2009-01-01

The purpose of this study was to establish baseline data regarding the adoption of iPods and similar technologies by agricultural science and technology teachers. The population consisted of all agricultural science and technology teachers in Texas. A sample of 310 was randomly drawn from the population. Study findings reveal that while…

Cluster-Randomized Trial to Increase Hepatitis B Testing among Koreans in Los Angeles

PubMed Central

Bastani, Roshan; Glenn, Beth A.; Maxwell, Annette E.; Jo, Angela M.; Herrmann, Alison K.; Crespi, Catherine M.; Wong, Weng K.; Chang, L. Cindy; Stewart, Susan L.; Nguyen, Tung T.; Chen, Moon S.; Taylor, Victoria M.

2015-01-01

Background In the United States, Korean immigrants experience a disproportionately high burden of chronic hepatitis B (HBV) viral infection and associated liver cancer compared to the general population. However, despite clear clinical guidelines, HBV serologic testing among Koreans remains persistently sub-optimal. Methods We conducted a cluster-randomized trial to evaluate a church-based small group intervention to improve HBV testing among Koreans in Los Angeles. Fifty-two Korean churches, stratified by size (small, medium, large) and location (Koreatown versus other), were randomized to intervention or control conditions. Intervention church participants attended a single-session small-group discussion on liver cancer and HBV testing and control church participants attended a similar session on physical activity and nutrition. Outcome data consisted of self-reported HBV testing obtained via 6-month telephone follow-up interviews. Results We recruited 1123 individuals, 18-64 years of age, across the 52 churches. Ninety-two percent of the sample attended the assigned intervention session and 86% completed the 6-month follow-up. Sample characteristics included: mean age 46 years, 65% female, 97% born in Korea, 69% completed some college, and 43% insured. In an intent-to-treat analysis, the intervention produced a statistically significant effect (OR = 4.9, p < .001), with 19% of intervention and 6% of control group participants reporting a HBV test. Conclusion Our intervention was successful in achieving a large and robust effect in a population at high risk of HBV infection and sequelae. Impact The intervention was fairly resource efficient and thus has high potential for replication in other high-risk Asian groups. PMID:26104909

Visiting Entertainment Venues and Sexual Health in China

PubMed Central

Li, Li; Wu, Zunyou; Rotheram-Borus, Mary Jane; Guan, Jihui; Yin, Yueping; Detels, Roger; Wu, Sheng; Lee, Sung-Jae; Cao, Haijun; Lin, Chunqing; Rou, Keming; Liu, Zhendong

2010-01-01

Entertainment venues in China are associated with risky sexual behavior. Most previous studies related to entertainment venues in China have focused on sex workers and commercial sex, but this study addressed sexual health in a sample of the general urban population. A randomly selected sample of market vendors (n = 4,510) from an eastern city was recruited and assessed to examine relationships between entertainment venue visits and sexual risk. Both behavioral (self-reports of unprotected sex) and biomedical (STD test results) measures were used. About 18% of the sample (26.8% of men and 9% of women) reported visiting entertainment venues in the past 30 days. Those who visited entertainment venues were more likely to be male, younger, single, with higher education, and to have more discretionary income. For both men and women, visiting entertainment venues was a significant predictor for unprotected sex and STD infection. Gender differences were observed in predicting unprotected sex and STD infections. Entertainment venues could be potential sites for place-based intervention programs and out-reach for the general population. PMID:18256918

Lifetime Prevalence of Suicide Attempts Among Sexual Minority Adults by Study Sampling Strategies: A Systematic Review and Meta-Analysis.

PubMed

Hottes, Travis Salway; Bogaert, Laura; Rhodes, Anne E; Brennan, David J; Gesink, Dionne

2016-05-01

Previous reviews have demonstrated a higher risk of suicide attempts for lesbian, gay, and bisexual (LGB) persons (sexual minorities), compared with heterosexual groups, but these were restricted to general population studies, thereby excluding individuals sampled through LGB community venues. Each sampling strategy, however, has particular methodological strengths and limitations. For instance, general population probability studies have defined sampling frames but are prone to information bias associated with underreporting of LGB identities. By contrast, LGB community surveys may support disclosure of sexuality but overrepresent individuals with strong LGB community attachment. To reassess the burden of suicide-related behavior among LGB adults, directly comparing estimates derived from population- versus LGB community-based samples. In 2014, we searched MEDLINE, EMBASE, PsycInfo, CINAHL, and Scopus databases for articles addressing suicide-related behavior (ideation, attempts) among sexual minorities. We selected quantitative studies of sexual minority adults conducted in nonclinical settings in the United States, Canada, Europe, Australia, and New Zealand. Random effects meta-analysis and meta-regression assessed for a difference in prevalence of suicide-related behavior by sample type, adjusted for study or sample-level variables, including context (year, country), methods (medium, response rate), and subgroup characteristics (age, gender, sexual minority construct). We examined residual heterogeneity by using τ(2). We pooled 30 cross-sectional studies, including 21,201 sexual minority adults, generating the following lifetime prevalence estimates of suicide attempts: 4% (95% confidence interval [CI] = 3%, 5%) for heterosexual respondents to population surveys, 11% (95% CI = 8%, 15%) for LGB respondents to population surveys, and 20% (95% CI = 18%, 22%) for LGB respondents to community surveys (Figure 1). The difference in LGB estimates by sample type persisted after we accounted for covariates with meta-regression. Sample type explained 33% of the between-study variability. Regardless of sample type examined, sexual minorities had a higher lifetime prevalence of suicide attempts than heterosexual persons; however, the magnitude of this disparity was contingent upon sample type. Community-based surveys of LGB people suggest that 20% of sexual minority adults have attempted suicide. Accurate estimates of sexual minority health disparities are necessary for public health monitoring and research. Most data describing these disparities are derived from 2 sample types, which yield different estimates of the lifetime prevalence of suicide attempts. Additional studies should explore the differential effects of selection and information biases on the 2 predominant sampling approaches used to understand sexual minority health.

Development of a spatial sampling protocol using GIS to measure health disparities in Bobo-Dioulasso, Burkina Faso, a medium-sized African city.

PubMed

Kassié, Daouda; Roudot, Anna; Dessay, Nadine; Piermay, Jean-Luc; Salem, Gérard; Fournet, Florence

2017-04-18

Many cities in developing countries experience an unplanned and rapid growth. Several studies have shown that the irregular urbanization and equipment of cities produce different health risks and uneven exposure to specific diseases. Consequently, health surveys within cities should be carried out at the micro-local scale and sampling methods should try to capture this urban diversity. This article describes the methodology used to develop a multi-stage sampling protocol to select a population for a demographic survey that investigates health disparities in the medium-sized city of Bobo-Dioulasso, Burkina Faso. It is based on the characterization of Bobo-Dioulasso city typology by taking into account the city heterogeneity, as determined by analysis of the built environment and of the distribution of urban infrastructures, such as healthcare structures or even water fountains, by photo-interpretation of aerial photographs and satellite images. Principal component analysis and hierarchical ascendant classification were then used to generate the city typology. Five groups of spaces with specific profiles were identified according to a set of variables which could be considered as proxy indicators of health status. Within these five groups, four sub-spaces were randomly selected for the study. We were then able to survey 1045 households in all the selected sub-spaces. The pertinence of this approach is discussed regarding to classical sampling as random walk method for example. This urban space typology allowed to select a population living in areas representative of the uneven urbanization process, and to characterize its health status in regards to several indicators (nutritional status, communicable and non-communicable diseases, and anaemia). Although this method should be validated and compared with more established methods, it appears as an alternative in developing countries where geographic and population data are scarce.

The Hi Five study: design of a school-based randomized trial to reduce infections and improve hygiene and well-being among 6-15 year olds in Denmark.

PubMed

Johansen, Anette; Denbæk, Anne Maj; Bonnesen, Camilla Thørring; Due, Pernille

2015-03-01

Infectious illnesses such as influenza and diarrhea are leading causes of absenteeism among Danish school children. Interventions in school settings addressing hand hygiene have shown to reduce the number of infectious illnesses. However, most of these studies include small populations and almost none of them are conducted as randomized controlled trials. The overall aim of the Hi Five study was to develop, implement and evaluate a multi-component school-based intervention to improve hand hygiene and well-being and to reduce the prevalence of infections among school children in intervention schools by 20% compared to control schools. This paper describes the development and the evaluation design of Hi Five. The Hi Five study was designed as a tree-armed cluster-randomized controlled trial. A national random sample of schools (n = 44) was randomized to one of two intervention groups (n = 29) or to a control group with no intervention (n = 15). A total of 8,438 six to fifteen-year-old school children were enrolled in the study. The Hi Five intervention consisted of three components: 1) a curriculum component 2) mandatory daily hand washing before lunch 3) extra cleaning of school toilets during the school day. Baseline data was collected from December 2011 to April 2012. The intervention period was August 2012 to June 2013. The follow-up data was collected from December 2012 to April 2013. The Hi Five study fills a gap in international research. This large randomized multi-component school-based hand hygiene intervention is the first to include education on healthy and appropriate toilet behavior as part of the curriculum. No previous studies have involved supplementary cleaning at the school toilets as an intervention component. The study will have the added value of providing new knowledge about usability of short message service (SMS, text message) for collecting data on infectious illness and absenteeism in large study populations. Current Controlled Trials ISRCTN19287682 , 21 December 2012.

U.S. consumer demand for restaurant calorie information: targeting demographic and behavioral segments in labeling initiatives.

PubMed

Kolodinsky, Jane; Reynolds, Travis William; Cannella, Mark; Timmons, David; Bromberg, Daniel

2009-01-01

To identify different segments of U.S. consumers based on food choices, exercise patterns, and desire for restaurant calorie labeling. Using a stratified (by region) random sample of the U.S. population, trained interviewers collected data for this cross-sectional study through telephone surveys. Center for Rural Studies U.S. national health survey. The final sample included 580 responses (22% response rate); data were weighted to be representative of age and gender characteristics of the U.S. population. Self-reported behaviors related to food choices, exercise patterns, desire for calorie information in restaurants, and sample demographics. Clusters were identified using Schwartz Bayesian criteria. Impacts of demographic characteristics on cluster membership were analyzed using bivariate tests of association and multinomial logit regression. Cluster analysis revealed three clusters based on respondents' food choices, activity levels, and desire for restaurant labeling. Two clusters, comprising three quarters of the sample, desired calorie labeling in restaurants. The remaining cluster opposed restaurant labeling. Demographic variables significantly predicting cluster membership included region of residence (p < .10), income (p < .05), gender (p < .01), and age (p < .10). Though limited by a low response and potential self-reporting bias in the phone survey, this study suggests that several groups are likely to benefit from restaurant calorie labeling. Specific demographic clusters could be targeted through labeling initiatives.

Differences between blood donors and a population sample: implications for case-control studies.

PubMed

Golding, Jean; Northstone, Kate; Miller, Laura L; Davey Smith, George; Pembrey, Marcus

2013-08-01

Selecting appropriate controls for studies of genetic variation in case series is important. The two major candidates involve the use of blood donors or a random sample of the population. We compare and contrast the two different populations of controls for studies of genetic variation using data from parents enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). In addition we compute different biases using a series of hypothetical assumptions. The study subjects who had been blood donors differed markedly from the general population in social, health-related, anthropometric, and personality-related variables. Using theoretical examples, we show that blood donors are a poor control group for non-genetic studies of diseases related to environmentally, behaviourally, or socially patterned exposures. However, we show that if blood donors are used as controls in genetic studies, these factors are unlikely to make a major difference in detecting true associations with relatively rare disorders (cumulative incidence through life of <10%). Nevertheless, for more common disorders, the reduction in accuracy resulting from the inclusion in any control population of individuals who have or will develop the disease in question can create a greater bias than can socially patterned factors. Information about the medical history of a control and the parents of the control (as a proxy for whether the control will develop the disease) is more important with regard to the choice of controls than whether the controls are a random population sample or blood donors.

An Innovative Multiphased Strategy to Recruit Underserved Adults into a Randomized Trial of a Community-Based Diabetes Risk Reduction Program

PubMed Central

Santoyo-Olsson, Jasmine; Cabrera, Julissa; Freyre, Rachel; Grossman, Melanie; Alvarez, Natalie; Mathur, Deepika; Guerrero, Maria; Delgadillo, Adriana T.; Kanaya, Alka M.; Stewart, Anita L.

2011-01-01

Purpose: To conduct and evaluate a two-phased community-based approach to recruit lower socioeconomic status, minority, or Spanish-speaking adults at risk of developing diabetes to a randomized trial of a lifestyle intervention program delivered by a public health department. Design: Within geographic areas comprising our target population, 4 community organizations provided local space for conducting the study and program. Phase I—outreach in venues surrounding these organizations—included diabetes education, a short diabetes risk appraisal (DRA), and diabetes risk screening based on a fasting fingerstick glucose test. Phase II—trial recruitment—began concurrently for those found to be at risk of developing diabetes in Phase I by explaining the study, lifestyle program, and research process. Those interested and eligible enrolled in the 1-year study. Results: Over 2 years, approximately 5,110 individuals received diabetes education, 1,917 completed a DRA, and 1,164 were screened of which 641 (55%) had an elevated fingerstick result of ≥106 mg/dl. Of the study sampling frame—persons over age 25 at risk of developing diabetes (N = 544)—238 (43%) enrolled in the trial; of those who were study eligible (n = 427), 56% enrolled. In the final sample, mean age was 56 years (SD = 17), 78% were ethnic minorities, 32% were Spanish-speaking, and 15% had a high school education or less. Implications: Providing diabetes health education and screening prior to study recruitment may help overcome barriers to research participation in underserved communities, thus helping address difficulties recruiting minority and older populations into research, particularly research pertaining to chronic disease risk factors. PMID:21565823

MHC-correlated mate choice in humans: a review.

PubMed

Havlicek, Jan; Roberts, S Craig

2009-05-01

Extremely high variability in genes of the major histocompatibility complex (MHC) in vertebrates is assumed to be a consequence of frequency-dependent parasite-driven selection and mate preferences based on promotion of offspring heterozygosity at MHC, or potentially, genome-wide inbreeding avoidance. Where effects have been found, mate choice studies on rodents and other species usually find preference for MHC-dissimilarity in potential partners. Here we critically review studies on MHC-associated mate choice in humans. These are based on three broadly different aspects: (1) odor preferences, (2) facial preferences and (3) actual mate choice surveys. As in animal studies, most odor-based studies demonstrate disassortative preferences, although there is variation in the strength and nature of the effects. In contrast, facial attractiveness research indicates a preference for MHC-similar individuals. Results concerning MHC in actual couples show a bias towards similarity in one study, dissimilarity in two studies and random distribution in several other studies. These vary greatly in sample size and heterogeneity of the sample population, both of which may significantly bias the results. This pattern of mixed results across studies may reflect context-dependent and/or life history sensitive preference expression, in addition to higher level effects arising out of population differences in genetic heterogeneity or cultural and ethnic restrictions on random mating patterns. Factors of special relevance in terms of individual preferences are reproductive status and long- vs. short-term mating context. We discuss the idea that olfactory and visual channels may work in a complementary way (i.e. odor preference for MHC-dissimilarity and visual preference for MHC-similarity) to achieve an optimal level of genetic variability, methodological issues and interesting avenues for further research.

Abdominal obesity and its association with health-related quality of life in adults: a population-based study in five Chinese cities

PubMed Central

2014-01-01

Background This study aimed to investigate the prevalence of abdominal obesity and its association with the health-related quality of life (HRQOL) in a randomly selected Chinese sample. Methods A population-based sample of 3,600 residents aged 18–80 years was selected randomly from 5 Chinese cities. Demographic information, and waist and hip circumference measurements were obtained. The Mandarin version of the Short Form 36 Health Survey questionnaire (SF-36) was used to assess the HRQOL. Waist circumference (WC) and waist-to-hip ratio (WHR) were used as measures of abdominal obesity, and the prevalence of abdominal obesity and its association with HRQOL were analysed. Results Among the 3,184 participants included in the analysis, the prevalence of abdominal obesity was about 45% in both women and men as evaluated by WC, and about 40% in women and 33% in men as evaluated by WHR. The prevalence varied by city, region, age, marital status, education level, family income, smoking, and the presence of chronic diseases. Both WC and WHR increased with age, and men had larger WC and WHR than women in most age groups. In women, abdominal obesity, as determined by both WC and WHR, was associated with meaningful impairments in 4 physical health scales and 2 mental health scales. In men, abdominal obesity, as determined by WC, was associated with 1 physical health scale and 1 mental health scale, and it was associated with 2 physical health scales based on WHR. Conclusions Physical health, but not mental health, was more vulnerable to impairment with abdominal obesity, and the impairments varied between genders. Public health agencies should emphasize that abdominal obesity impairs physical health. PMID:24925310

Locomotor problems among rural elderly population in a District of Aligarh, North India.

PubMed

Maroof, Mohd; Ahmad, Anees; Khalique, Najam; Ansari, M Athar

2017-01-01

Locomotor functions decline with the age along with other physiological changes. This results in deterioration of the quality of life with decreased social and economic role in the society, as well as increased dependency, for the health care and other basic services. The demographic transition resulting in increased proportion of elderly may pose a burden to the health system. To find the prevalence of locomotor problems among the elderly population, and related sociodemographic factors. The study was a community-based cross-sectional study done at field practice area of Rural Health Training Centre, JN Medical College, AMU, Aligarh, Uttar Pradesh, India. A sample of 225 was drawn from 1018 elderly population aged 60 years and above using systematic random sampling with probability proportionate to size. Sociodemographic characteristics were obtained using pretested and predesigned questionnaire. Locomotor problems were assessed using the criteria used by National Sample Survey Organization. Data were analyzed using SPSS version 20. Chi-square test was used to test relationship of locomotor problems with sociodemographic factors. P <0.05 was considered statistically significant. The prevalence of locomotor problems among the elderly population was 25.8%. Locomotor problems were significantly associated with age, gender, and working status whereas no significant association with literacy status and marital status was observed. The study concluded that approximately one-fourth of the elderly population suffered from locomotor problems. The sociodemographic factors related to locomotor problems needs to be addressed properly to help them lead an independent and economically productive life.

The effect of newly induced mutations on the fitness of genotypes and populations of yeast (Saccharomyces cerevisiae).

PubMed

Orthen, E; Lange, P; Wöhrmann, K

1984-12-01

This paper analyses the fate of artificially induced mutations and their importance to the fitness of populations of the yeast, Saccharomyces cerevisiae, an increasingly important model organism in population genetics. Diploid strains, treated with UV and EMS, were cultured asexually for approximately 540 generations and under conditions where the asexual growth was interrupted by a sexual phase. Growth rates of 100 randomly sampled diploid clones were estimated at the beginning and at the end of the experiment. After the induction of sporulation the growth rates of 100 randomly sampled spores were measured. UV and EMS treatment decreases the average growth rate of the clones significantly but increases the variability in comparison to the untreated control. After selection over approximately 540 generations, variability in growth rates was reduced to that of the untreated control. No increase in mean population fitness was observed. However, the results show that after selection there still exists a large amount of hidden genetic variability in the populations which is revealed when the clones are cultivated in environments other than those in which selection took place. A sexual phase increased the reduction of the induced variability.

Sampling western spruce budworm larvae by frequency of occurrence on lower crown branches.

Treesearch

R.R. Mason; R.C. Beckwith

1990-01-01

A sampling method was derived whereby budworm density can be estimated by the frequency of occurrence of larvae over a given threshold number instead of by direct counts on branch samples. The model used for converting frequencies to mean densities is appropriate for nonrandom as well as random distributions and, therefore, is applicable to all population densities of...

Operationalizing multimorbidity and autonomy for health services research in aging populations - the OMAHA study

PubMed Central

2011-01-01

Background As part of a Berlin-based research consortium on health in old age, the OMAHA (Operationalizing Multimorbidity and Autonomy for Health Services Research in Aging Populations) study aims to develop a conceptual framework and a set of standardized instruments and indicators for continuous monitoring of multimorbidity and associated health care needs in the population 65 years and older. Methods/Design OMAHA is a longitudinal epidemiological study including a comprehensive assessment at baseline and at 12-month follow-up as well as brief intermediate telephone interviews at 6 and 18 months. In order to evaluate different sampling procedures and modes of data collection, the study is conducted in two different population-based samples of men and women aged 65 years and older. A geographically defined sample was recruited from an age and sex stratified random sample from the register of residents in Berlin-Mitte (Berlin OMAHA study cohort, n = 299) for assessment by face-to-face interview and examination. A larger nationwide sample (German OMAHA study cohort, n = 730) was recruited for assessment by telephone interview among participants in previous German Telephone Health Surveys. In both cohorts, we successfully applied a multi-dimensional set of instruments to assess multimorbidity, functional disability in daily life, autonomy, quality of life (QoL), health care services utilization, personal and social resources as well as socio-demographic and biographical context variables. Response rates considerably varied between the Berlin and German OMAHA study cohorts (22.8% vs. 59.7%), whereas completeness of follow-up at month 12 was comparably high in both cohorts (82.9% vs. 81.2%). Discussion The OMAHA study offers a wide spectrum of data concerning health, functioning, social involvement, psychological well-being, and cognitive capacity in community-dwelling older people in Germany. Results from the study will add to methodological and content-specific discourses on human resources for maintaining quality of life and autonomy throughout old age, even in the face of multiple health complaints. PMID:21352521

Prevalence Incidence Mixture Models

Cancer.gov

The R package and webtool fits Prevalence Incidence Mixture models to left-censored and irregularly interval-censored time to event data that is commonly found in screening cohorts assembled from electronic health records. Absolute and relative risk can be estimated for simple random sampling, and stratified sampling (the two approaches of superpopulation and a finite population are supported for target populations). Non-parametric (absolute risks only), semi-parametric, weakly-parametric (using B-splines), and some fully parametric (such as the logistic-Weibull) models are supported.

PM2.5 Population Exposure in New Delhi Using a Probabilistic Simulation Framework.

PubMed

Saraswat, Arvind; Kandlikar, Milind; Brauer, Michael; Srivastava, Arun

2016-03-15

This paper presents a Geographical Information System (GIS) based probabilistic simulation framework to estimate PM2.5 population exposure in New Delhi, India. The framework integrates PM2.5 output from spatiotemporal LUR models and trip distribution data using a Gravity model based on zonal data for population, employment and enrollment in educational institutions. Time-activity patterns were derived from a survey of randomly sampled individuals (n = 1012) and in-vehicle exposure was estimated using microenvironmental monitoring data based on field measurements. We simulated population exposure for three different scenarios to capture stay-at-home populations (Scenario 1), working population exposed to near-road concentrations during commutes (Scenario 2), and the working population exposed to on-road concentrations during commutes (Scenario 3). Simulated annual average levels of PM2.5 exposure across the entire city were very high, and particularly severe in the winter months: ∼200 μg m(-3) in November, roughly four times higher compared to the lower levels in the monsoon season. Mean annual exposures ranged from 109 μg m(-3) (IQR: 97-120 μg m(-3)) for Scenario 1, to 121 μg m(-3) (IQR: 110-131 μg m(-3)), and 125 μg m(-3) (IQR: 114-136 μ gm(-3)) for Scenarios 2 and 3 respectively. Ignoring the effects of mobility causes the average annual PM2.5 population exposure to be underestimated by only 11%.

Design and simulation study of the immunization Data Quality Audit (DQA).

PubMed

Woodard, Stacy; Archer, Linda; Zell, Elizabeth; Ronveaux, Olivier; Birmingham, Maureen

2007-08-01

The goal of the Data Quality Audit (DQA) is to assess whether the Global Alliance for Vaccines and Immunization-funded countries are adequately reporting the number of diphtheria-tetanus-pertussis immunizations given, on which the "shares" are awarded. Given that this sampling design is a modified two-stage cluster sample (modified because a stratified, rather than a simple, random sample of health facilities is obtained from the selected clusters); the formula for the calculation of the standard error for the estimate is unknown. An approximated standard error has been proposed, and the first goal of this simulation is to assess the accuracy of the standard error. Results from the simulations based on hypothetical populations were found not to be representative of the actual DQAs that were conducted. Additional simulations were then conducted on the actual DQA data to better access the precision of the DQ with both the original and the increased sample sizes.

Statistical and population genetics issues of two Hungarian datasets from the aspect of DNA evidence interpretation.

PubMed

Szabolcsi, Zoltán; Farkas, Zsuzsa; Borbély, Andrea; Bárány, Gusztáv; Varga, Dániel; Heinrich, Attila; Völgyi, Antónia; Pamjav, Horolma

2015-11-01

When the DNA profile from a crime-scene matches that of a suspect, the weight of DNA evidence depends on the unbiased estimation of the match probability of the profiles. For this reason, it is required to establish and expand the databases that reflect the actual allele frequencies in the population applied. 21,473 complete DNA profiles from Databank samples were used to establish the allele frequency database to represent the population of Hungarian suspects. We used fifteen STR loci (PowerPlex ESI16) including five, new ESS loci. The aim was to calculate the statistical, forensic efficiency parameters for the Databank samples and compare the newly detected data to the earlier report. The population substructure caused by relatedness may influence the frequency of profiles estimated. As our Databank profiles were considered non-random samples, possible relationships between the suspects can be assumed. Therefore, population inbreeding effect was estimated using the FIS calculation. The overall inbreeding parameter was found to be 0.0106. Furthermore, we tested the impact of the two allele frequency datasets on 101 randomly chosen STR profiles, including full and partial profiles. The 95% confidence interval estimates for the profile frequencies (pM) resulted in a tighter range when we used the new dataset compared to the previously published ones. We found that the FIS had less effect on frequency values in the 21,473 samples than the application of minimum allele frequency. No genetic substructure was detected by STRUCTURE analysis. Due to the low level of inbreeding effect and the high number of samples, the new dataset provides unbiased and precise estimates of LR for statistical interpretation of forensic casework and allows us to use lower allele frequencies. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Prevalence of depressive disorders in the elderly.

PubMed

Barua, Ankur; Ghosh, Mihir Kumar; Kar, Nilamadhab; Basilio, Mary Anne

2011-01-01

Community-based mental health studies have revealed that the point prevalence of depressive disorders in the elderly population of the world varies between 10% and 20%, depending on cultural situations. A retrospective study based on analysis of various study reports was conducted, to determine the median prevalence rates of depressive disorders in the elderly population of India and various other countries in the world. All the studies that constituted the sample were conducted between 1955 and 2005. Included are only community-based, cross-sectional surveys and some prospective studies that had not excluded depression at baseline. These studies were conducted on a homogenous community of the elderly population in the world, who were selected by a simple random sampling technique. After applying the inclusion and exclusion criteria on published and indexed articles, 74 original research studies that surveyed a total of 487,275 elderly individuals, in the age group of 60 years and above, residing in various parts of the world, were included for the final analysis. The median prevalence rate and its corresponding interquartile range were calculated. The chi-square test and chi-square for linear trend were applied. A P value of <.05 was considered as statistically significant. The median prevalence rate of depressive disorders in the world for the elderly population was determined to be 10.3% (interquartile range [IQR], 4.7%-16.0%). The median prevalence rate of depression among the elderly Indian population was determined to be 21.9% (IQR, 11.6%-31.1%). Although there was a significant decrease in the trend of world prevalence of geriatric depression, it was significantly higher among Indians, in recent years, than the rest of the world.

Performance review using sequential sampling and a practice computer.

PubMed

Difford, F

1988-06-01

The use of sequential sample analysis for repeated performance review is described with examples from several areas of practice. The value of a practice computer in providing a random sample from a complete population, evaluating the parameters of a sequential procedure, and producing a structured worksheet is discussed. It is suggested that sequential analysis has advantages over conventional sampling in the area of performance review in general practice.

An Assessment on Awareness and Acceptability of Child Adoption in Edo State

ERIC Educational Resources Information Center

Aluyor, P.; Salami, L. I.

2017-01-01

The study examines the awareness and acceptability of child adoption in Edo State. The design used for the study was survey design. The population for the study is made up of adults male and female in Esan West Local Government Area. One hundred respondents were randomly selected using random sampling techniques. The validity was ascertained by…

Estimating population salt intake in India using spot urine samples.

PubMed

Petersen, Kristina S; Johnson, Claire; Mohan, Sailesh; Rogers, Kris; Shivashankar, Roopa; Thout, Sudhir Raj; Gupta, Priti; He, Feng J; MacGregor, Graham A; Webster, Jacqui; Santos, Joseph Alvin; Krishnan, Anand; Maulik, Pallab K; Reddy, K Srinath; Gupta, Ruby; Prabhakaran, Dorairaj; Neal, Bruce

2017-11-01

To compare estimates of mean population salt intake in North and South India derived from spot urine samples versus 24-h urine collections. In a cross-sectional survey, participants were sampled from slum, urban and rural communities in North and in South India. Participants provided 24-h urine collections, and random morning spot urine samples. Salt intake was estimated from the spot urine samples using a series of established estimating equations. Salt intake data from the 24-h urine collections and spot urine equations were weighted to provide estimates of salt intake for Delhi and Haryana, and Andhra Pradesh. A total of 957 individuals provided a complete 24-h urine collection and a spot urine sample. Weighted mean salt intake based on the 24-h urine collection, was 8.59 (95% confidence interval 7.73-9.45) and 9.46 g/day (8.95-9.96) in Delhi and Haryana, and Andhra Pradesh, respectively. Corresponding estimates based on the Tanaka equation [9.04 (8.63-9.45) and 9.79 g/day (9.62-9.96) for Delhi and Haryana, and Andhra Pradesh, respectively], the Mage equation [8.80 (7.67-9.94) and 10.19 g/day (95% CI 9.59-10.79)], the INTERSALT equation [7.99 (7.61-8.37) and 8.64 g/day (8.04-9.23)] and the INTERSALT equation with potassium [8.13 (7.74-8.52) and 8.81 g/day (8.16-9.46)] were all within 1 g/day of the estimate based upon 24-h collections. For the Toft equation, estimates were 1-2 g/day higher [9.94 (9.24-10.64) and 10.69 g/day (9.44-11.93)] and for the Kawasaki equation they were 3-4 g/day higher [12.14 (11.30-12.97) and 13.64 g/day (13.15-14.12)]. In urban and rural areas in North and South India, most spot urine-based equations provided reasonable estimates of mean population salt intake. Equations that did not provide good estimates may have failed because specimen collection was not aligned with the original method.

[The research protocol III. Study population].

PubMed

Arias-Gómez, Jesús; Villasís-Keever, Miguel Ángel; Miranda-Novales, María Guadalupe

2016-01-01

The study population is defined as a set of cases, determined, limited, and accessible, that will constitute the subjects for the selection of the sample, and must fulfill several characteristics and distinct criteria. The objectives of this manuscript are focused on specifying each one of the elements required to make the selection of the participants of a research project, during the elaboration of the protocol, including the concepts of study population, sample, selection criteria and sampling methods. After delineating the study population, the researcher must specify the criteria that each participant has to comply. The criteria that include the specific characteristics are denominated selection or eligibility criteria. These criteria are inclusion, exclusion and elimination, and will delineate the eligible population. The sampling methods are divided in two large groups: 1) probabilistic or random sampling and 2) non-probabilistic sampling. The difference lies in the employment of statistical methods to select the subjects. In every research, it is necessary to establish at the beginning the specific number of participants to be included to achieve the objectives of the study. This number is the sample size, and can be calculated or estimated with mathematical formulas and statistic software.

Employing a Multi-level Approach to Recruit a Representative Sample of Women with Recent Gestational Diabetes Mellitus into a Randomized Lifestyle Intervention Trial.

PubMed

Nicklas, Jacinda M; Skurnik, Geraldine; Zera, Chloe A; Reforma, Liberty G; Levkoff, Sue E; Seely, Ellen W

2016-02-01

The postpartum period is a window of opportunity for diabetes prevention in women with recent gestational diabetes (GDM), but recruitment for clinical trials during this period of life is a major challenge. We adapted a social-ecologic model to develop a multi-level recruitment strategy at the macro (high or institutional level), meso (mid or provider level), and micro (individual) levels. Our goal was to recruit 100 women with recent GDM into the Balance after Baby randomized controlled trial over a 17-month period. Participants were asked to attend three in-person study visits at 6 weeks, 6, and 12 months postpartum. They were randomized into a control arm or a web-based intervention arm at the end of the baseline visit at six weeks postpartum. At the end of the recruitment period, we compared population characteristics of our enrolled subjects to the entire population of women with GDM delivering at Brigham and Women's Hospital (BWH). We successfully recruited 107 of 156 (69 %) women assessed for eligibility, with the majority (92) recruited during pregnancy at a mean 30 (SD ± 5) weeks of gestation, and 15 recruited postpartum, at a mean 2 (SD ± 3) weeks postpartum. 78 subjects attended the initial baseline visit, and 75 subjects were randomized into the trial at a mean 7 (SD ± 2) weeks postpartum. The recruited subjects were similar in age and race/ethnicity to the total population of 538 GDM deliveries at BWH over the 17-month recruitment period. Our multilevel approach allowed us to successfully meet our recruitment goal and recruit a representative sample of women with recent GDM. We believe that our most successful strategies included using a dedicated in-person recruiter, integrating recruitment into clinical flow, allowing for flexibility in recruitment, minimizing barriers to participation, and using an opt-out strategy with providers. Although the majority of women were recruited while pregnant, women recruited in the early postpartum period were more likely to present for the first study visit. Given the increased challenges of recruiting postpartum women with GDM into research studies, we believe our findings will be useful to other investigators seeking to study this population.

Methods for sampling geographically mobile female traders in an East African market setting

PubMed Central

Achiro, Lillian; Kwena, Zachary A.; McFarland, Willi; Neilands, Torsten B.; Cohen, Craig R.; Bukusi, Elizabeth A.; Camlin, Carol S.

2018-01-01

Background The role of migration in the spread of HIV in sub-Saharan Africa is well-documented. Yet migration and HIV research have often focused on HIV risks to male migrants and their partners, or migrants overall, often failing to measure the risks to women via their direct involvement in migration. Inconsistent measures of mobility, gender biases in those measures, and limited data sources for sex-specific population-based estimates of mobility have contributed to a paucity of research on the HIV prevention and care needs of migrant and highly mobile women. This study addresses an urgent need for novel methods for developing probability-based, systematic samples of highly mobile women, focusing on a population of female traders operating out of one of the largest open air markets in East Africa. Our method involves three stages: 1.) identification and mapping of all market stall locations using Global Positioning System (GPS) coordinates; 2.) using female market vendor stall GPS coordinates to build the sampling frame using replicates; and 3.) using maps and GPS data for recruitment of study participants. Results The location of 6,390 vendor stalls were mapped using GPS. Of these, 4,064 stalls occupied by women (63.6%) were used to draw four replicates of 128 stalls each, and a fifth replicate of 15 pre-selected random alternates for a total of 527 stalls assigned to one of five replicates. Staff visited 323 stalls from the first three replicates and from these successfully recruited 306 female vendors into the study for a participation rate of 94.7%. Mobilization strategies and involving traders association representatives in participant recruitment were critical to the study’s success. Conclusion The study’s high participation rate suggests that this geospatial sampling method holds promise for development of probability-based samples in other settings that serve as transport hubs for highly mobile populations. PMID:29324780

Internet Exposure Associated With Canadian Parents' Perception of Risk on Childhood Immunization: Cross-Sectional Study.

PubMed

Tustin, Jordan Lee; Crowcroft, Natasha Sarah; Gesink, Dionne; Johnson, Ian; Keelan, Jennifer

2018-01-19

There is a large presence of provaccination and antivaccination content on the Internet. The Internet has been identified as an important source for parents to seek and share vaccine information. There are concerns that parental fears or hesitancy on childhood immunizations are increasing due to the popularity of social media and exposure to online antivaccination sentiment. No other studies have investigated the association between seeking vaccine information online and Canadian parents' perception of risk on childhood immunization. We aimed to investigate the potential association between seeking vaccine information on the Internet and Canadian parents' perception of risk on childhood immunization in order to quantify the perceived association and increase our understanding on the impact of the Internet to help guide public health interventions. We analyzed this association in two population samples: a self-selecting Web-based sample of Canadian parents recruited through Facebook (n=966) and a population-based sample of parents recruited by random digit dialing (RDD; n=951). The outcome was parental perception of vaccine safety on a seven-point ordinal scale from "not safe" to "extremely safe." An ordinal regression model was used to investigate if Internet information seeking on childhood vaccination predicted parental perception of vaccine safety. After adjusting for income level, Internet reliability, age of parent, and region, the odds of perceiving vaccines as less safe rather than more safe were 1.6 times higher (95% CI 1.3-2.1) for parents who used the Internet to search for vaccination information compared to parents who did not search the Internet in the Web-based sample, and 2.0 times higher (95% CI 1.6-2.5) in the population-based RDD sample. The results suggest the Internet is significantly associated with Canadian parents' negative perception of vaccine risk. Governmental and scientific sectors should consider the development and implementation of Web-based vaccine interventions to promote confidence in immunization. ©Jordan Lee Tustin, Natasha Sarah Crowcroft, Dionne Gesink, Ian Johnson, Jennifer Keelan. Originally published in JMIR Public Health and Surveillance (http://publichealth.jmir.org), 19.01.2018.

Animated Randomness, Avatars, Movement, and Personalization in Risk Graphics

PubMed Central

Fuhrel-Forbis, Andrea; Wijeysundera, Harindra C; Exe, Nicole; Dickson, Mark; Holtzman, Lisa; Kahn, Valerie C; Zikmund-Fisher, Brian J

2014-01-01

Background Risk communication involves conveying two inherently difficult concepts about the nature of risk: the underlying random distribution of outcomes and how a population-based proportion applies to an individual. Objective The objective of this study was to test whether 4 design factors in icon arrays—animated random dispersal of risk events, avatars to represent an individual, personalization (operationalized as choosing the avatar’s color), and a moving avatar—might help convey randomness and how a given risk applies to an individual, thereby better aligning risk perceptions with risk estimates. Methods A diverse sample of 3630 adults with no previous heart disease or stroke completed an online nested factorial experiment in which they entered personal health data into a risk calculator that estimated 10-year risk of cardiovascular disease based on a robust and validated model. We randomly assigned them to view their results in 1 of 10 risk graphics that used different combinations of the 4 design factors. We measured participants’ risk perceptions as our primary outcome, as well as behavioral intentions and recall of the risk estimate. We also assessed subjective numeracy, whether or not participants knew anyone who had died of cardiovascular causes, and whether or not they knew their blood pressure and cholesterol as potential moderators. Results Animated randomness was associated with better alignment between risk estimates and risk perceptions (F 1,3576=6.12, P=.01); however, it also led to lower scores on healthy lifestyle intentions (F 1,3572=11.1, P<.001). Using an avatar increased risk perceptions overall (F 1,3576=4.61, P=.03) and most significantly increased risk perceptions among those who did not know a particular person who had experienced the grave outcomes of cardiovascular disease (F 1,3576=5.88, P=.02). Using an avatar also better aligned actual risk estimates with intentions to see a doctor (F 1,3556=6.38, P=.01). No design factors had main effects on recall, but animated randomness was associated with better recall for those at lower risk and worse recall for those at higher risk (F 1,3544=7.06, P=.01). Conclusions Animated randomness may help people better understand the random nature of risk. However, in the context of cardiovascular risk, such understanding may result in lower healthy lifestyle intentions. Therefore, whether or not to display randomness may depend on whether one’s goal is to persuade or to inform. Avatars show promise for helping people grasp how population-based statistics map to an individual case. PMID:24642037

Population genetic structure of the blue-fronted Amazon (Amazona aestiva, Psittacidae: Aves) based on nuclear microsatellite loci: implications for conservation.

PubMed

Leite, K C E; Seixas, G H F; Berkunsky, I; Collevatti, R G; Caparroz, R

2008-09-09

The blue-fronted Amazon (Amazona aestiva) is a widely distributed Neotropical parrot and one of the most captured parrots in nature to supply the illegal trade of wild animals. The objectives of the present study were to analyze the genetic structure of A. aestiva to identify management units and support conservation planning and to verified if A. aestiva populations have undergone a recent bottleneck due to habitat loss and capture for the pet trade. The genetic structure was accessed by analyzing six microsatellite loci in 74 individuals of A. aestiva, including samples from the two subspecies (A. a. aestiva and A. a. xanthopteryx), from five populations: four in Brazil and one in Argentina. A significant genetic differentiation (theta = 0.007, p = 0.005) could be detected only between the most distant populations, Tocantins and Argentina, localized at the northeast and southwest limits of the sample sites, respectively. There was no evidence of inbreeding within or between populations, suggesting random mating among individuals. These results suggest a clinal distribution of genetic variability, as observed for variation in plumage color of the two A. aestiva subspecies. Bottleneck analysis did not show a recent reduction in population size. Thus, for the management and conservation of the species, the populations from Argentina and Tocantins should be considered as different management units, and the other populations from the center of the geographical distribution as another management unit.

Sample and population exponents of generalized Taylor's law.

PubMed

Giometto, Andrea; Formentin, Marco; Rinaldo, Andrea; Cohen, Joel E; Maritan, Amos

2015-06-23

Taylor's law (TL) states that the variance V of a nonnegative random variable is a power function of its mean M; i.e., V = aM(b). TL has been verified extensively in ecology, where it applies to population abundance, physics, and other natural sciences. Its ubiquitous empirical verification suggests a context-independent mechanism. Sample exponents b measured empirically via the scaling of sample mean and variance typically cluster around the value b = 2. Some theoretical models of population growth, however, predict a broad range of values for the population exponent b pertaining to the mean and variance of population density, depending on details of the growth process. Is the widely reported sample exponent b ≃ 2 the result of ecological processes or could it be a statistical artifact? Here, we apply large deviations theory and finite-sample arguments to show exactly that in a broad class of growth models the sample exponent is b ≃ 2 regardless of the underlying population exponent. We derive a generalized TL in terms of sample and population exponents b(jk) for the scaling of the kth vs. the jth cumulants. The sample exponent b(jk) depends predictably on the number of samples and for finite samples we obtain b(jk) ≃ k = j asymptotically in time, a prediction that we verify in two empirical examples. Thus, the sample exponent b ≃ 2 may indeed be a statistical artifact and not dependent on population dynamics under conditions that we specify exactly. Given the broad class of models investigated, our results apply to many fields where TL is used although inadequately understood.

Discrimination of fish populations using parasites: Random Forests on a 'predictable' host-parasite system.

PubMed

Pérez-Del-Olmo, A; Montero, F E; Fernández, M; Barrett, J; Raga, J A; Kostadinova, A

2010-10-01

We address the effect of spatial scale and temporal variation on model generality when forming predictive models for fish assignment using a new data mining approach, Random Forests (RF), to variable biological markers (parasite community data). Models were implemented for a fish host-parasite system sampled along the Mediterranean and Atlantic coasts of Spain and were validated using independent datasets. We considered 2 basic classification problems in evaluating the importance of variations in parasite infracommunities for assignment of individual fish to their populations of origin: multiclass (2-5 population models, using 2 seasonal replicates from each of the populations) and 2-class task (using 4 seasonal replicates from 1 Atlantic and 1 Mediterranean population each). The main results are that (i) RF are well suited for multiclass population assignment using parasite communities in non-migratory fish; (ii) RF provide an efficient means for model cross-validation on the baseline data and this allows sample size limitations in parasite tag studies to be tackled effectively; (iii) the performance of RF is dependent on the complexity and spatial extent/configuration of the problem; and (iv) the development of predictive models is strongly influenced by seasonal change and this stresses the importance of both temporal replication and model validation in parasite tagging studies.

The risk-stratified osteoporosis strategy evaluation study (ROSE): a randomized prospective population-based study. Design and baseline characteristics.

PubMed

Rubin, Katrine Hass; Holmberg, Teresa; Rothmann, Mette Juel; Høiberg, Mikkel; Barkmann, Reinhard; Gram, Jeppe; Hermann, Anne Pernille; Bech, Mickael; Rasmussen, Ole; Glüer, Claus C; Brixen, Kim

2015-02-01

The risk-stratified osteoporosis strategy evaluation study (ROSE) is a randomized prospective population-based study investigating the effectiveness of a two-step screening program for osteoporosis in women. This paper reports the study design and baseline characteristics of the study population. 35,000 women aged 65-80 years were selected at random from the population in the Region of Southern Denmark and-before inclusion-randomized to either a screening group or a control group. As first step, a self-administered questionnaire regarding risk factors for osteoporosis based on FRAX(®) was issued to both groups. As second step, subjects in the screening group with a 10-year probability of major osteoporotic fractures ≥15% were offered a DXA scan. Patients diagnosed with osteoporosis from the DXA scan were advised to see their GP and discuss pharmaceutical treatment according to Danish National guidelines. The primary outcome is incident clinical fractures as evaluated through annual follow-up using the Danish National Patient Registry. The secondary outcomes are cost-effectiveness, participation rate, and patient preferences. 20,904 (60%) women participated and included in the baseline analyses (10,411 in screening and 10,949 in control group). The mean age was 71 years. As expected by randomization, the screening and control groups had similar baseline characteristics. Screening for osteoporosis is at present not evidence based according to the WHO screening criteria. The ROSE study is expected to provide knowledge of the effectiveness of a screening strategy that may be implemented in health care systems to prevent fractures.

Inadequacy of Conventional Grab Sampling for Remediation Decision-Making for Metal Contamination at Small-Arms Ranges.

PubMed

Clausen, J L; Georgian, T; Gardner, K H; Douglas, T A

2018-01-01

Research shows grab sampling is inadequate for evaluating military ranges contaminated with energetics because of their highly heterogeneous distribution. Similar studies assessing the heterogeneous distribution of metals at small-arms ranges (SAR) are lacking. To address this we evaluated whether grab sampling provides appropriate data for performing risk analysis at metal-contaminated SARs characterized with 30-48 grab samples. We evaluated the extractable metal content of Cu, Pb, Sb, and Zn of the field data using a Monte Carlo random resampling with replacement (bootstrapping) simulation approach. Results indicate the 95% confidence interval of the mean for Pb (432 mg/kg) at one site was 200-700 mg/kg with a data range of 5-4500 mg/kg. Considering the U.S. Environmental Protection Agency screening level for lead is 400 mg/kg, the necessity of cleanup at this site is unclear. Resampling based on populations of 7 and 15 samples, a sample size more realistic for the area yielded high false negative rates.

Alcohol consumption and cardiorespiratory fitness in five population-based studies.

PubMed

Baumeister, Sebastian E; Finger, Jonas D; Gläser, Sven; Dörr, Marcus; Markus, Marcello Rp; Ewert, Ralf; Felix, Stephan B; Grabe, Hans-Jörgen; Bahls, Martin; Mensink, Gert Bm; Völzke, Henry; Piontek, Katharina; Leitzmann, Michael F

2018-01-01

Background Poor cardiorespiratory fitness is a risk factor for cardiovascular morbidity. Alcohol consumption contributes substantially to the burden of disease, but its association with cardiorespiratory fitness is not well described. We examined associations between average alcohol consumption, heavy episodic drinking and cardiorespiratory fitness. Design The design of this study was as a cross-sectional population-based random sample. Methods We analysed data from five independent population-based studies (Study of Health in Pomerania (2008-2012); German Health Interview and Examination Survey (2008-2011); US National Health and Nutrition Examination Survey (NHANES) 1999-2000; NHANES 2001-2002; NHANES 2003-2004) including 7358 men and women aged 20-85 years, free of lung disease or asthma. Cardiorespiratory fitness, quantified by peak oxygen uptake, was assessed using exercise testing. Information regarding average alcohol consumption (ethanol in grams per day (g/d)) and heavy episodic drinking (5+ or 6+ drinks/occasion) was obtained from self-reports. Fractional polynomial regression models were used to determine the best-fitting dose-response relationship. Results Average alcohol consumption displayed an inverted U-type relation with peak oxygen uptake ( p-value<0.0001), after adjustment for age, sex, education, smoking and physical activity. Compared to individuals consuming 10 g/d (moderate consumption), current abstainers and individuals consuming 50 and 60 g/d had significantly lower peak oxygen uptake values (ml/kg/min) (β coefficients = -1.90, β = -0.06, β = -0.31, respectively). Heavy episodic drinking was not associated with peak oxygen uptake. Conclusions Across multiple adult population-based samples, moderate drinkers displayed better fitness than current abstainers and individuals with higher average alcohol consumption.

Understanding and comparisons of different sampling approaches for the Fourier Amplitudes Sensitivity Test (FAST)

PubMed Central

Xu, Chonggang; Gertner, George

2013-01-01

Fourier Amplitude Sensitivity Test (FAST) is one of the most popular uncertainty and sensitivity analysis techniques. It uses a periodic sampling approach and a Fourier transformation to decompose the variance of a model output into partial variances contributed by different model parameters. Until now, the FAST analysis is mainly confined to the estimation of partial variances contributed by the main effects of model parameters, but does not allow for those contributed by specific interactions among parameters. In this paper, we theoretically show that FAST analysis can be used to estimate partial variances contributed by both main effects and interaction effects of model parameters using different sampling approaches (i.e., traditional search-curve based sampling, simple random sampling and random balance design sampling). We also analytically calculate the potential errors and biases in the estimation of partial variances. Hypothesis tests are constructed to reduce the effect of sampling errors on the estimation of partial variances. Our results show that compared to simple random sampling and random balance design sampling, sensitivity indices (ratios of partial variances to variance of a specific model output) estimated by search-curve based sampling generally have higher precision but larger underestimations. Compared to simple random sampling, random balance design sampling generally provides higher estimation precision for partial variances contributed by the main effects of parameters. The theoretical derivation of partial variances contributed by higher-order interactions and the calculation of their corresponding estimation errors in different sampling schemes can help us better understand the FAST method and provide a fundamental basis for FAST applications and further improvements. PMID:24143037

Understanding and comparisons of different sampling approaches for the Fourier Amplitudes Sensitivity Test (FAST).

PubMed

Xu, Chonggang; Gertner, George

2011-01-01

Fourier Amplitude Sensitivity Test (FAST) is one of the most popular uncertainty and sensitivity analysis techniques. It uses a periodic sampling approach and a Fourier transformation to decompose the variance of a model output into partial variances contributed by different model parameters. Until now, the FAST analysis is mainly confined to the estimation of partial variances contributed by the main effects of model parameters, but does not allow for those contributed by specific interactions among parameters. In this paper, we theoretically show that FAST analysis can be used to estimate partial variances contributed by both main effects and interaction effects of model parameters using different sampling approaches (i.e., traditional search-curve based sampling, simple random sampling and random balance design sampling). We also analytically calculate the potential errors and biases in the estimation of partial variances. Hypothesis tests are constructed to reduce the effect of sampling errors on the estimation of partial variances. Our results show that compared to simple random sampling and random balance design sampling, sensitivity indices (ratios of partial variances to variance of a specific model output) estimated by search-curve based sampling generally have higher precision but larger underestimations. Compared to simple random sampling, random balance design sampling generally provides higher estimation precision for partial variances contributed by the main effects of parameters. The theoretical derivation of partial variances contributed by higher-order interactions and the calculation of their corresponding estimation errors in different sampling schemes can help us better understand the FAST method and provide a fundamental basis for FAST applications and further improvements.

Revisiting sample size: are big trials the answer?

PubMed

Lurati Buse, Giovanna A L; Botto, Fernando; Devereaux, P J

2012-07-18

The superiority of the evidence generated in randomized controlled trials over observational data is not only conditional to randomization. Randomized controlled trials require proper design and implementation to provide a reliable effect estimate. Adequate random sequence generation, allocation implementation, analyses based on the intention-to-treat principle, and sufficient power are crucial to the quality of a randomized controlled trial. Power, or the probability of the trial to detect a difference when a real difference between treatments exists, strongly depends on sample size. The quality of orthopaedic randomized controlled trials is frequently threatened by a limited sample size. This paper reviews basic concepts and pitfalls in sample-size estimation and focuses on the importance of large trials in the generation of valid evidence.

A two-stage cluster sampling method using gridded population data, a GIS, and Google Earth(TM) imagery in a population-based mortality survey in Iraq.

PubMed

Galway, Lp; Bell, Nathaniel; Sae, Al Shatari; Hagopian, Amy; Burnham, Gilbert; Flaxman, Abraham; Weiss, Wiliam M; Rajaratnam, Julie; Takaro, Tim K

2012-04-27

Mortality estimates can measure and monitor the impacts of conflict on a population, guide humanitarian efforts, and help to better understand the public health impacts of conflict. Vital statistics registration and surveillance systems are rarely functional in conflict settings, posing a challenge of estimating mortality using retrospective population-based surveys. We present a two-stage cluster sampling method for application in population-based mortality surveys. The sampling method utilizes gridded population data and a geographic information system (GIS) to select clusters in the first sampling stage and Google Earth TM imagery and sampling grids to select households in the second sampling stage. The sampling method is implemented in a household mortality study in Iraq in 2011. Factors affecting feasibility and methodological quality are described. Sampling is a challenge in retrospective population-based mortality studies and alternatives that improve on the conventional approaches are needed. The sampling strategy presented here was designed to generate a representative sample of the Iraqi population while reducing the potential for bias and considering the context specific challenges of the study setting. This sampling strategy, or variations on it, are adaptable and should be considered and tested in other conflict settings.

A two-stage cluster sampling method using gridded population data, a GIS, and Google EarthTM imagery in a population-based mortality survey in Iraq

PubMed Central

2012-01-01

Background Mortality estimates can measure and monitor the impacts of conflict on a population, guide humanitarian efforts, and help to better understand the public health impacts of conflict. Vital statistics registration and surveillance systems are rarely functional in conflict settings, posing a challenge of estimating mortality using retrospective population-based surveys. Results We present a two-stage cluster sampling method for application in population-based mortality surveys. The sampling method utilizes gridded population data and a geographic information system (GIS) to select clusters in the first sampling stage and Google Earth TM imagery and sampling grids to select households in the second sampling stage. The sampling method is implemented in a household mortality study in Iraq in 2011. Factors affecting feasibility and methodological quality are described. Conclusion Sampling is a challenge in retrospective population-based mortality studies and alternatives that improve on the conventional approaches are needed. The sampling strategy presented here was designed to generate a representative sample of the Iraqi population while reducing the potential for bias and considering the context specific challenges of the study setting. This sampling strategy, or variations on it, are adaptable and should be considered and tested in other conflict settings. PMID:22540266

Genetic polymorphisms in MDR1, CYP3A4 and CYP3A5 genes in a Ghanaian population: a plausible explanation for altered metabolism of ivermectin in humans?

PubMed Central

2010-01-01

Background Ivermectin, a substrate of multidrug resistance (MDR1) gene and cytochrome P450 (CYP) 3A4, has been used successfully in the treatment of onchocerciasis in Ghana. However, there have been reports of suboptimal response in some patients after repeated treatment. Polymorphisms in host MDR1 and CYP3A genes may explain the observed suboptimal response to ivermectin. We genotyped relevant functional polymorphisms of MDR1 and CYP3A in a random sample of healthy Ghanaians and compared the data with that of ivermectin-treated patients with a view to exploring the relationship between suboptimal response to ivermectin and MDR1 and CYP3A allelic frequencies. Methods Using PCR-RFLP, relevant polymorphic alleles of MDR1 and CYP3A4 genes were analysed in 204 randomly selected individuals and in 42 ivermectin treated patients. Results We recorded significantly higher MDR1 (3435T) variant allele frequency in suboptimal responders (21%) than in patients who responded to treatment (12%) or the random population sample (11%). CYP3A4*1B, CYP3A5*3 and CYP3A5*6 alleles were detected at varied frequencies for the sampled Ghanaian population, responders and suboptimal responders to ivermectin. CYP3A5*1/CYP3A5*1 and CYP3A5*1/CYP3A5*3 genotypes were also found to be significantly different for responders and suboptimal responders. Haplotype (*1/*1/*3/*1) was determined to be significantly different between responders and suboptimal responders indicating a possible role of these haplotypes in treatment response with ivermectin. Conclusion A profile of pharmacogenetically relevant variants for MDR1, CYP3A4 and CYP3A5 genes has been generated for a random population of 204 Ghanaians to address the scarcity of data within indigenous African populations. In 42 patients treated with ivermectin, difference in MDR1 variant allele frequency was observed between suboptimal responders and responders. PMID:20630055

Genetic polymorphisms in MDR1, CYP3A4 and CYP3A5 genes in a Ghanaian population: a plausible explanation for altered metabolism of ivermectin in humans?

PubMed

Kudzi, William; Dodoo, Alexander N O; Mills, Jeremy J

2010-07-14

Ivermectin, a substrate of multidrug resistance (MDR1) gene and cytochrome P450 (CYP) 3A4, has been used successfully in the treatment of onchocerciasis in Ghana. However, there have been reports of suboptimal response in some patients after repeated treatment. Polymorphisms in host MDR1 and CYP3A genes may explain the observed suboptimal response to ivermectin. We genotyped relevant functional polymorphisms of MDR1 and CYP3A in a random sample of healthy Ghanaians and compared the data with that of ivermectin-treated patients with a view to exploring the relationship between suboptimal response to ivermectin and MDR1 and CYP3A allelic frequencies. Using PCR-RFLP, relevant polymorphic alleles of MDR1 and CYP3A4 genes were analysed in 204 randomly selected individuals and in 42 ivermectin treated patients. We recorded significantly higher MDR1 (3435T) variant allele frequency in suboptimal responders (21%) than in patients who responded to treatment (12%) or the random population sample (11%). CYP3A4*1B, CYP3A5*3 and CYP3A5*6 alleles were detected at varied frequencies for the sampled Ghanaian population, responders and suboptimal responders to ivermectin. CYP3A5*1/CYP3A5*1 and CYP3A5*1/CYP3A5*3 genotypes were also found to be significantly different for responders and suboptimal responders. Haplotype (*1/*1/*3/*1) was determined to be significantly different between responders and suboptimal responders indicating a possible role of these haplotypes in treatment response with ivermectin. A profile of pharmacogenetically relevant variants for MDR1, CYP3A4 and CYP3A5 genes has been generated for a random population of 204 Ghanaians to address the scarcity of data within indigenous African populations. In 42 patients treated with ivermectin, difference in MDR1 variant allele frequency was observed between suboptimal responders and responders.

A simple and efficient alternative to implementing systematic random sampling in stereological designs without a motorized microscope stage.

PubMed

Melvin, Neal R; Poda, Daniel; Sutherland, Robert J

2007-10-01

When properly applied, stereology is a very robust and efficient method to quantify a variety of parameters from biological material. A common sampling strategy in stereology is systematic random sampling, which involves choosing a random sampling [corrected] start point outside the structure of interest, and sampling relevant objects at [corrected] sites that are placed at pre-determined, equidistant intervals. This has proven to be a very efficient sampling strategy, and is used widely in stereological designs. At the microscopic level, this is most often achieved through the use of a motorized stage that facilitates the systematic random stepping across the structure of interest. Here, we report a simple, precise and cost-effective software-based alternative to accomplishing systematic random sampling under the microscope. We believe that this approach will facilitate the use of stereological designs that employ systematic random sampling in laboratories that lack the resources to acquire costly, fully automated systems.

Using auxiliary information to improve wildlife disease surveillance when infected animals are not detected: a Bayesian approach

USGS Publications Warehouse

Heisey, Dennis M.; Jennelle, Christopher S.; Russell, Robin E.; Walsh, Daniel P.

2014-01-01

There are numerous situations in which it is important to determine whether a particular disease of interest is present in a free-ranging wildlife population. However adequate disease surveillance can be labor-intensive and expensive and thus there is substantial motivation to conduct it as efficiently as possible. Surveillance is often based on the assumption of a simple random sample, but this can almost always be improved upon if there is auxiliary information available about disease risk factors. We present a Bayesian approach to disease surveillance when auxiliary risk information is available which will usually allow for substantial improvements over simple random sampling. Others have employed risk weights in surveillance, but this can result in overly optimistic statements regarding freedom from disease due to not accounting for the uncertainty in the auxiliary information; our approach remedies this. We compare our Bayesian approach to a published example of risk weights applied to chronic wasting disease in deer in Colorado, and we also present calculations to examine when uncertainty in the auxiliary information has a serious impact on the risk weights approach. Our approach allows “apples-to-apples” comparisons of surveillance efficiencies between units where heterogeneous samples were collected

Forensic timber identification: a case study of a CITES listed species, Gonystylus bancanus (Thymelaeaceae).

PubMed

Ng, Kevin Kit Siong; Lee, Soon Leong; Tnah, Lee Hong; Nurul-Farhanah, Zakaria; Ng, Chin Hong; Lee, Chai Ting; Tani, Naoki; Diway, Bibian; Lai, Pei Sing; Khoo, Eyen

2016-07-01

Illegal logging and smuggling of Gonystylus bancanus (Thymelaeaceae) poses a serious threat to this fragile valuable peat swamp timber species. Using G. bancanus as a case study, DNA markers were used to develop identification databases at the species, population and individual level. The species level database for Gonystylus comprised of an rDNA (ITS2) and two cpDNA (trnH-psbA and trnL) markers based on a 20 Gonystylus species database. When concatenated, taxonomic species recognition was achieved with a resolution of 90% (18 out of the 20 species). In addition, based on 17 natural populations of G. bancanus throughout West (Peninsular Malaysia) and East (Sabah and Sarawak) Malaysia, population and individual identification databases were developed using cpDNA and STR markers respectively. A haplotype distribution map for Malaysia was generated using six cpDNA markers, resulting in 12 unique multilocus haplotypes, from 24 informative intraspecific variable sites. These unique haplotypes suggest a clear genetic structuring of West and East regions. A simulation procedure based on the composition of the samples was used to test whether a suspected sample conformed to a given regional origin. Overall, the observed type I and II errors of the databases showed good concordance with the predicted 5% threshold which indicates that the databases were useful in revealing provenance and establishing conformity of samples from West and East Malaysia. Sixteen STRs were used to develop the DNA profiling databases for individual identification. Bayesian clustering analyses divided the 17 populations into two main genetic clusters, corresponding to the regions of West and East Malaysia. Population substructuring (K=2) was observed within each region. After removal of bias resulting from sampling effects and population subdivision, conservativeness tests showed that the West and East Malaysia databases were conservative. This suggests that both databases can be used independently for random match probability estimation within respective regions. The reliability of the databases was further determined by independent self-assignment tests based on the likelihood of each individual's multilocus genotype occurring in each identified population, genetic cluster and region with an average percentage of correctly assigned individuals of 54.80%, 99.60% and 100% respectively. Thus, after appropriate validation, the genetic identification databases developed for G. bancanus in this study could support forensic applications and help safeguard this valuable species into the future. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Effect of an educational toolkit on quality of care: a pragmatic cluster randomized trial.

PubMed

Shah, Baiju R; Bhattacharyya, Onil; Yu, Catherine H Y; Mamdani, Muhammad M; Parsons, Janet A; Straus, Sharon E; Zwarenstein, Merrick

2014-02-01

Printed educational materials for clinician education are one of the most commonly used approaches for quality improvement. The objective of this pragmatic cluster randomized trial was to evaluate the effectiveness of an educational toolkit focusing on cardiovascular disease screening and risk reduction in people with diabetes. All 933,789 people aged ≥40 years with diagnosed diabetes in Ontario, Canada were studied using population-level administrative databases, with additional clinical outcome data collected from a random sample of 1,592 high risk patients. Family practices were randomly assigned to receive the educational toolkit in June 2009 (intervention group) or May 2010 (control group). The primary outcome in the administrative data study, death or non-fatal myocardial infarction, occurred in 11,736 (2.5%) patients in the intervention group and 11,536 (2.5%) in the control group (p = 0.77). The primary outcome in the clinical data study, use of a statin, occurred in 700 (88.1%) patients in the intervention group and 725 (90.1%) in the control group (p = 0.26). Pre-specified secondary outcomes, including other clinical events, processes of care, and measures of risk factor control, were also not improved by the intervention. A limitation is the high baseline rate of statin prescribing in this population. The educational toolkit did not improve quality of care or cardiovascular outcomes in a population with diabetes. Despite being relatively easy and inexpensive to implement, printed educational materials were not effective. The study highlights the need for a rigorous and scientifically based approach to the development, dissemination, and evaluation of quality improvement interventions. http://www.ClinicalTrials.gov NCT01411865 and NCT01026688.

The use of propensity scores to assess the generalizability of results from randomized trials

PubMed Central

Stuart, Elizabeth A.; Cole, Stephen R.; Bradshaw, Catherine P.; Leaf, Philip J.

2014-01-01

Randomized trials remain the most accepted design for estimating the effects of interventions, but they do not necessarily answer a question of primary interest: Will the program be effective in a target population in which it may be implemented? In other words, are the results generalizable? There has been very little statistical research on how to assess the generalizability, or “external validity,” of randomized trials. We propose the use of propensity-score-based metrics to quantify the similarity of the participants in a randomized trial and a target population. In this setting the propensity score model predicts participation in the randomized trial, given a set of covariates. The resulting propensity scores are used first to quantify the difference between the trial participants and the target population, and then to match, subclassify, or weight the control group outcomes to the population, assessing how well the propensity score-adjusted outcomes track the outcomes actually observed in the population. These metrics can serve as a first step in assessing the generalizability of results from randomized trials to target populations. This paper lays out these ideas, discusses the assumptions underlying the approach, and illustrates the metrics using data on the evaluation of a schoolwide prevention program called Positive Behavioral Interventions and Supports. PMID:24926156

A Study on Chocolate Consumption in Prospective Teachers

ERIC Educational Resources Information Center

Ozgen, Leyla

2016-01-01

This study was planned and conducted to determine the chocolate consumption habits of prospective teachers. The study population was comprised of students attending the Faculty of Education at Gazi University in Ankara and the sample consisted of 251 prospective teachers selected with simple random sampling. 96.4% and 3.6% of the prospective…

Predicting Posttraumatic Stress Symptoms Longitudinally in a Representative Sample of Hospitalized Injured Adolescents

ERIC Educational Resources Information Center

Zatzick, Douglas F.; Grossman, David C.; Russo, Joan; Pynoos, Robert; Berliner, Lucy; Jurkovich, Gregory; Sabin, Janice A.; Katon, Wayne; Ghesquiere, Angela; McCauley, Elizabeth; Rivara, Frederick P.

2006-01-01

Objective: Adolescents constitute a high-risk population for traumatic physical injury, yet few longitudinal investigations have assessed the development of posttraumatic stress disorder (PTSD) symptoms over time in representative samples. Method: Between July 2002 and August 2003,108 randomly selected injured adolescent patients ages 12 to 18 and…

Simulation-Extrapolation for Estimating Means and Causal Effects with Mismeasured Covariates

ERIC Educational Resources Information Center

Lockwood, J. R.; McCaffrey, Daniel F.

2015-01-01

Regression, weighting and related approaches to estimating a population mean from a sample with nonrandom missing data often rely on the assumption that conditional on covariates, observed samples can be treated as random. Standard methods using this assumption generally will fail to yield consistent estimators when covariates are measured with…

Teaching materials of algebraic equation

NASA Astrophysics Data System (ADS)

Widodo, S. A.; Prahmana, R. C. I.; Purnami, A. S.; Turmudi

2017-12-01

The purpose of this paper is to know the effectiveness of teaching materials algebraic equation. This type of research used experimental method. The population in this study is all students of mathematics education who take numerical method in sarjanawiyata tamansiswa of university; the sample is taken using cluster random sampling. Instrument used in this research is test and questionnaire. The test is used to know the problem solving ability and achievement, while the questionnaire is used to know the student's response on the teaching materials. Data Analysis technique of quantitative used Wilcoxon test, while the qualitative data used grounded theory. Based on the results of the test can be concluded that the development of teaching materials can improve the ability to solve problems and achievement.

The linear trend of headache prevalence and some headache features in school children.

PubMed

Ozge, Aynur; Buğdayci, Resul; Saşmaz, Tayyar; Kaleağasi, Hakan; Kurt, Oner; Karakelle, Ali; Siva, Aksel

2007-04-01

The objectives of this study were to determine the age and sex dependent linear trend of recurrent headache prevalence in schoolchildren in Mersin. A stratified sample composed of 5562 children; detailed characteristics were previously published. In this study the prevalence distribution of headache by age and sex showed a peak in the female population at the age of 11 (27.2%) with a plateau in the following years. The great stratified random sample results suggested that, in addition to socio-demographic features, detailed linear trend analysis showed headache features of children with headache have some specific characteristics dependent on age, gender and headache type. This study results can constitute a basis for the future epidemiological based studies.

The Self-Adapting Focused Review System. Probability sampling of medical records to monitor utilization and quality of care.

PubMed

Ash, A; Schwartz, M; Payne, S M; Restuccia, J D

1990-11-01

Medical record review is increasing in importance as the need to identify and monitor utilization and quality of care problems grow. To conserve resources, reviews are usually performed on a subset of cases. If judgment is used to identify subgroups for review, this raises the following questions: How should subgroups be determined, particularly since the locus of problems can change over time? What standard of comparison should be used in interpreting rates of problems found in subgroups? How can population problem rates be estimated from observed subgroup rates? How can the bias be avoided that arises because reviewers know that selected cases are suspected of having problems? How can changes in problem rates over time be interpreted when evaluating intervention programs? Simple random sampling, an alternative to subgroup review, overcomes the problems implied by these questions but is inefficient. The Self-Adapting Focused Review System (SAFRS), introduced and described here, provides an adaptive approach to record selection that is based upon model-weighted probability sampling. It retains the desirable inferential properties of random sampling while allowing reviews to be concentrated on cases currently thought most likely to be problematic. Model development and evaluation are illustrated using hospital data to predict inappropriate admissions.

An evaluation of the genetic-matched pair study design using genome-wide SNP data from the European population.

PubMed

Lu, Timothy Tehua; Lao, Oscar; Nothnagel, Michael; Junge, Olaf; Freitag-Wolf, Sandra; Caliebe, Amke; Balascakova, Miroslava; Bertranpetit, Jaume; Bindoff, Laurence Albert; Comas, David; Holmlund, Gunilla; Kouvatsi, Anastasia; Macek, Milan; Mollet, Isabelle; Nielsen, Finn; Parson, Walther; Palo, Jukka; Ploski, Rafal; Sajantila, Antti; Tagliabracci, Adriano; Gether, Ulrik; Werge, Thomas; Rivadeneira, Fernando; Hofman, Albert; Uitterlinden, André Gerardus; Gieger, Christian; Wichmann, Heinz-Erich; Ruether, Andreas; Schreiber, Stefan; Becker, Christian; Nürnberg, Peter; Nelson, Matthew Roberts; Kayser, Manfred; Krawczak, Michael

2009-07-01

Genetic matching potentially provides a means to alleviate the effects of incomplete Mendelian randomization in population-based gene-disease association studies. We therefore evaluated the genetic-matched pair study design on the basis of genome-wide SNP data (309,790 markers; Affymetrix GeneChip Human Mapping 500K Array) from 2457 individuals, sampled at 23 different recruitment sites across Europe. Using pair-wise identity-by-state (IBS) as a matching criterion, we tried to derive a subset of markers that would allow identification of the best overall matching (BOM) partner for a given individual, based on the IBS status for the subset alone. However, our results suggest that, by following this approach, the prediction accuracy is only notably improved by the first 20 markers selected, and increases proportionally to the marker number thereafter. Furthermore, in a considerable proportion of cases (76.0%), the BOM of a given individual, based on the complete marker set, came from a different recruitment site than the individual itself. A second marker set, specifically selected for ancestry sensitivity using singular value decomposition, performed even more poorly and was no more capable of predicting the BOM than randomly chosen subsets. This leads us to conclude that, at least in Europe, the utility of the genetic-matched pair study design depends critically on the availability of comprehensive genotype information for both cases and controls.

Assessment of generalizability, applicability and predictability (GAP) for evaluating external validity in studies of universal family-based prevention of alcohol misuse in young people: systematic methodological review of randomized controlled trials.

PubMed

Fernandez-Hermida, Jose Ramon; Calafat, Amador; Becoña, Elisardo; Tsertsvadze, Alexander; Foxcroft, David R

2012-09-01

To assess external validity characteristics of studies from two Cochrane Systematic Reviews of the effectiveness of universal family-based prevention of alcohol misuse in young people. Two reviewers used an a priori developed external validity rating form and independently assessed three external validity dimensions of generalizability, applicability and predictability (GAP) in randomized controlled trials. The majority (69%) of the included 29 studies were rated 'unclear' on the reporting of sufficient information for judging generalizability from sample to study population. Ten studies (35%) were rated 'unclear' on the reporting of sufficient information for judging applicability to other populations and settings. No study provided an assessment of the validity of the trial end-point measures for subsequent mortality, morbidity, quality of life or other economic or social outcomes. Similarly, no study reported on the validity of surrogate measures using established criteria for assessing surrogate end-points. Studies evaluating the benefits of family-based prevention of alcohol misuse in young people are generally inadequate at reporting information relevant to generalizability of the findings or implications for health or social outcomes. Researchers, study authors, peer reviewers, journal editors and scientific societies should take steps to improve the reporting of information relevant to external validity in prevention trials. © 2012 The Authors. Addiction © 2012 Society for the Study of Addiction.

Physical and sexual violence, mental health indicators, and treatment seeking among street-based population groups in Tegucigalpa, Honduras.

PubMed

Rio Navarro, Javier; Cohen, Julien; Rocillo Arechaga, Eva; Zuniga, Edgardo

2012-05-01

To establish the prevalence of exposure to physical and sexual violence, mental health symptoms, and medical treatment-seeking behavior among three street-based subpopulation groups in Tegucigalpa, Honduras, and to assess the association between sociodemographic group, mental health indicators, and exposure to violence. An anonymous, cross-sectional survey among randomly selected street-based adolescents, adults, and commercial sex workers (CSWs) was undertaken at the end of 2010 in Tegucigalpa. Médecins Sans Frontières (MSF) mapped places where the study population gathers. Stratified probability samples were drawn for all groups, using two-stage random sampling. Trained MSF staff administered on-site standardized face-to-face questionnaires. Self-reported exposure to severe physical violence in the previous year was 20.9% among street-based adolescents, 28.8% among adults, and 30.6% among CSWs. For the physical violence event self-defined as most severe, 50.0% of the adolescents, 81.4% of the adults, and 70.6% of the CSWs sought medical treatment. Their exposure to severe sexual violence was 8.6%, 28.8%, and 59.2%, respectively. After exposure to the self-defined most severe sexual violence event, 14.3% of adolescents, 31.9% of adults, and 29.1% of CSWs sought treatment. Common mental health and substance abuse symptoms were highly prevalent and strongly associated with exposure to physical (odds ratio 4.5, P < 0.0001) and sexual (odds ratio 3.7, P = 0.0001) violence. Exposure to physical and sexual violence reached extreme levels among street-based subpopulations. Treatment-seeking behavior, particularly after severe sexual violence, was limited. The association of mental health and substance abuse symptoms with exposure to violence could lead to further victimization. Medical and psychological treatments targeting these groups are needed and could help decrease their vulnerability.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hudson, W.G.

Scapteriscus vicinus is the most important pest of turf and pasture grasses in Florida. This study develops a method of correlating sample results with true population density and provides the first quantitative information on spatial distribution and movement patterns of mole crickets. Three basic techniques for sampling mole crickets were compared: soil flushes, soil corer, and pitfall trapping. No statistical difference was found between the soil corer and soil flushing. Soil flushing was shown to be more sensitive to changes in population density than pitfall trapping. No technique was effective for sampling adults. Regression analysis provided a means of adjustingmore » for the effects of soil moisture and showed soil temperature to be unimportant in predicting efficiency of flush sampling. Cesium-137 was used to label females for subsequent location underground. Comparison of mean distance to nearest neighbor with the distance predicted by a random distribution model showed that the observed distance in the spring was significantly greater than hypothesized (Student's T-test, p < 0.05). Fall adult nearest neighbor distance was not different than predicted by the random distribution hypothesis.« less

Assessing the Relationship of Ancient and Modern Populations

PubMed Central

Schraiber, Joshua G.

2018-01-01

Genetic material sequenced from ancient samples is revolutionizing our understanding of the recent evolutionary past. However, ancient DNA is often degraded, resulting in low coverage, error-prone sequencing. Several solutions exist to this problem, ranging from simple approach, such as selecting a read at random for each site, to more complicated approaches involving genotype likelihoods. In this work, we present a novel method for assessing the relationship of an ancient sample with a modern population, while accounting for sequencing error and postmortem damage by analyzing raw reads from multiple ancient individuals simultaneously. We show that, when analyzing SNP data, it is better to sequence more ancient samples to low coverage: two samples sequenced to 0.5× coverage provide better resolution than a single sample sequenced to 2× coverage. We also examined the power to detect whether an ancient sample is directly ancestral to a modern population, finding that, with even a few high coverage individuals, even ancient samples that are very slightly diverged from the modern population can be detected with ease. When we applied our approach to European samples, we found that no ancient samples represent direct ancestors of modern Europeans. We also found that, as shown previously, the most ancient Europeans appear to have had the smallest effective population sizes, indicating a role for agriculture in modern population growth. PMID:29167200

The genealogy of samples in models with selection.

PubMed

Neuhauser, C; Krone, S M

1997-02-01

We introduce the genealogy of a random sample of genes taken from a large haploid population that evolves according to random reproduction with selection and mutation. Without selection, the genealogy is described by Kingman's well-known coalescent process. In the selective case, the genealogy of the sample is embedded in a graph with a coalescing and branching structure. We describe this graph, called the ancestral selection graph, and point out differences and similarities with Kingman's coalescent. We present simulations for a two-allele model with symmetric mutation in which one of the alleles has a selective advantage over the other. We find that when the allele frequencies in the population are already in equilibrium, then the genealogy does not differ much from the neutral case. This is supported by rigorous results. Furthermore, we describe the ancestral selection graph for other selective models with finitely many selection classes, such as the K-allele models, infinitely-many-alleles models. DNA sequence models, and infinitely-many-sites models, and briefly discuss the diploid case.

The Genealogy of Samples in Models with Selection

PubMed Central

Neuhauser, C.; Krone, S. M.

1997-01-01

We introduce the genealogy of a random sample of genes taken from a large haploid population that evolves according to random reproduction with selection and mutation. Without selection, the genealogy is described by Kingman's well-known coalescent process. In the selective case, the genealogy of the sample is embedded in a graph with a coalescing and branching structure. We describe this graph, called the ancestral selection graph, and point out differences and similarities with Kingman's coalescent. We present simulations for a two-allele model with symmetric mutation in which one of the alleles has a selective advantage over the other. We find that when the allele frequencies in the population are already in equilibrium, then the genealogy does not differ much from the neutral case. This is supported by rigorous results. Furthermore, we describe the ancestral selection graph for other selective models with finitely many selection classes, such as the K-allele models, infinitely-many-alleles models, DNA sequence models, and infinitely-many-sites models, and briefly discuss the diploid case. PMID:9071604

Generalizing the Network Scale-Up Method: A New Estimator for the Size of Hidden Populations*

PubMed Central

Feehan, Dennis M.; Salganik, Matthew J.

2018-01-01

The network scale-up method enables researchers to estimate the size of hidden populations, such as drug injectors and sex workers, using sampled social network data. The basic scale-up estimator offers advantages over other size estimation techniques, but it depends on problematic modeling assumptions. We propose a new generalized scale-up estimator that can be used in settings with non-random social mixing and imperfect awareness about membership in the hidden population. Further, the new estimator can be used when data are collected via complex sample designs and from incomplete sampling frames. However, the generalized scale-up estimator also requires data from two samples: one from the frame population and one from the hidden population. In some situations these data from the hidden population can be collected by adding a small number of questions to already planned studies. For other situations, we develop interpretable adjustment factors that can be applied to the basic scale-up estimator. We conclude with practical recommendations for the design and analysis of future studies. PMID:29375167

COMPARISON OF POPULATIONS OF MOULD SPECIES IN HOMES IN THE UK AND US USING MOLD-SPECIFIC QUANTITATIVE PCR (MSQPCR)

EPA Science Inventory

The goal of this research was to compare the populations of 81 mold species in homes in USA and UK using mould specific quantitative polymerase chain reaction (MSQPCR) technology. Dust samples were obtained from randomly selected homes in Great Britain (n=11). The mould populat...

Rural Economic Development Consequences of the Population Turnaround in Northern Lower Michigan.

ERIC Educational Resources Information Center

West, Patrick C.; And Others

Consequences of population turnaround for rural economic development are examined in a 9-county region of Northern Lower Michigan. Data from census reports and 374 usable responses to a questionnaire mailed to a random sample of property owners drawn from 1982 county tax assessment rolls were used to test competing hypotheses about rural…

An aging population: relationships between socio-demographics, motivations and participation

Treesearch

Karen Robinson; Robert C. Burns; Chad D. Pierskalla; Alan Graefe

2008-01-01

The purpose of this study was to examine the outdoor recreation behavior of Oregon's aging population, including developing a socio-demographic profile and examining the importance of their current motivations with the importance of their expected motivations 10 years from now. A stratified random sample was drawn of Oregon residents, and a mailback questionnaire...

[Genetic variability and differentiation of three Russian populations of yellow potato cyst nematode Globodera rostochiensis as revealed by nuclear markers].

PubMed

Khrisanfova, G G; Kharchevnikov, D A; Popov, I O; Zinov'eva, S V; Semenova, S K

2008-05-01

Genetic variability of yellow potato cyst nematode G. rostochiensis from three Russian populations (Karelia, Vladimir oblast, and Moscow oblast) was investigated using two types of nuclear markers. Using RAPD markers identified with the help of six random primers (P-29, OPA-10, OPT-14, OPA-11, OPB-11, and OPH-20), it was possible to distinguish Karelian population from the group consisting of the populations from two adjacent regions (Moscow oblast and Vladimir oblast). Based on the combined matrix, containing 294 RAPD fragments, dendrogram of genetic differences was constructed, and the indices of genetic divergence and partition (P, H, and G(st)), as well as the gene flow indices N(m) between the nematode samples examined, were calculated. The dendrogram structure, genetic diversity indices, and variations of genetic distances between single individuals in each population from Karelia and Central Russia pointed to genetic isolation and higher genetic diversity of the nematodes from Karelia. Based on polymorphism of rDNA first intergenic spacer ITS1, attribution of all populations examined to the species G. rostochiensis was proved. Small variations of the ITS1 sequence in different geographic populations of nematodes from different regions of the species world range did not allow isolation of separate groups within the species. Possible factors (including interregional transportations of seed potato) affecting nematode population structure in Russia are discussed.

Do children with grapheme-colour synaesthesia show cognitive benefits?

PubMed

Simner, Julia; Bain, Angela E

2018-02-01

Grapheme-colour synaesthesia is characterized by conscious and consistent associations between letters and colours, or between numbers and colours (e.g., synaesthetes might see A as red, 7 as green). Our study explored the development of this condition in a group of randomly sampled child synaesthetes. Two previous studies (Simner & Bain, 2013, Frontiers in Human Neuroscience, 7, 603; Simner, Harrold, Creed, Monro, & Foulkes, 2009, Brain, 132, 57) had screened over 600 primary school children to find the first randomly sampled cohort of child synaesthetes. In this study, we evaluate this cohort to ask whether their synaesthesia is associated with a particular cognitive profile of strengths and/or weaknesses. We tested our child synaesthetes at age 10-11 years in a series of cognitive tests, in comparison with matched controls and baseline norms. One previous study (Green & Goswami, 2008, Cognition, 106, 463) had suggested that child synaesthetes might perform differently to non-synaesthetes in such tasks, although those participants may have been a special type of population independent of their synaesthesia. In our own study of randomly sampled child synaesthetes, we found no significant advantages or disadvantages in a receptive vocabulary test and a memory matrix task. However, we found that synaesthetes demonstrated above-average performance in a processing-speed task and a near-significant advantage in a letter-span task (i.e., memory/recall task of letters). Our findings point to advantages for synaesthetes that go beyond those expected from enhanced coding accounts and we present the first picture of the broader cognitive profile of a randomly sampled population of child synaesthetes. © 2017 The British Psychological Society.

Practical quantum random number generator based on measuring the shot noise of vacuum states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen Yong; Zou Hongxin; Tian Liang

2010-06-15

The shot noise of vacuum states is a kind of quantum noise and is totally random. In this paper a nondeterministic random number generation scheme based on measuring the shot noise of vacuum states is presented and experimentally demonstrated. We use a homodyne detector to measure the shot noise of vacuum states. Considering that the frequency bandwidth of our detector is limited, we derive the optimal sampling rate so that sampling points have the least correlation with each other. We also choose a method to extract random numbers from sampling values, and prove that the influence of classical noise canmore » be avoided with this method so that the detector does not have to be shot-noise limited. The random numbers generated with this scheme have passed ent and diehard tests.« less

COPD prevalence in a random population survey: a matter of definition.

PubMed

Shirtcliffe, P; Weatherall, M; Marsh, S; Travers, J; Hansell, A; McNaughton, A; Aldington, S; Muellerova, H; Beasley, R

2007-08-01

A recent American Thoracic Society and European Respiratory Society joint Task Force report recommends using a lower limit of normal (LLN) of forced expiratory volume in one second/forced vital capacity as opposed to a fixed ratio of <0.7 to diagnose airflow obstruction, in order to reduce false positive diagnoses of chronic obstructive pulmonary disease (COPD) as defined by the Global Initiative for Obstructive Lung Disease (GOLD). To date, there is no reliable spirometry-based prevalence data for COPD in New Zealand and the effect of different definitions of airflow obstruction based on post-bronchodilator spirometry is not known. Detailed written questionnaires, full pulmonary function tests (including pre- and post-bronchodilator flow-volume loops) and atopy testing were completed in 749 subjects recruited from a random population sample. The GOLD-defined, age-adjusted prevalence (95% confidence interval) for adults aged >or=40 yrs was 14.2 (11.0-17.0)% compared with an LLN-defined, age-adjusted, post-bronchodilator prevalence in the same group of 9.0 (6.7-11.3)%. The prevalence of chronic obstructive pulmonary disease varied markedly depending on the definition used. Further research using longitudinal rather than cross-sectional data will help decide the preferred approach in chronic obstructive pulmonary disease prevalence surveys.

Occurence of internet addiction in a general population sample: a latent class analysis.

PubMed

Rumpf, Hans-Jürgen; Vermulst, Ad A; Bischof, Anja; Kastirke, Nadin; Gürtler, Diana; Bischof, Gallus; Meerkerk, Gert-Jan; John, Ulrich; Meyer, Christian

2014-01-01

Prevalence studies of Internet addiction in the general population are rare. In addition, a lack of approved criteria hampers estimation of its occurrence. This study conducted a latent class analysis (LCA) in a large general population sample to estimate prevalence. A telephone survey was conducted based on a random digit dialling procedure including landline telephone (n=14,022) and cell phone numbers (n=1,001) in participants aged 14-64. The Compulsive Internet Use Scale (CIUS) served as the basis for a LCA used to look for subgroups representing participants with Internet addiction or at-risk use. CIUS was given to participants reporting to use the Internet for private purposes at least 1 h on a typical weekday or at least 1 h on a day at the weekend (n=8,130). A 6-class model showed best model fit and included two groups likely to represent Internet addiction and at-risk Internet use. Both groups showed less social participation and the Internet addiction group less general trust in other people. Proportions of probable Internet addiction were 1.0% (CI 0.9-1.2) among the entire sample, 2.4% (CI 1.9-3.1) in the age group 14-24, and 4.0% (CI 2.7-5.7) in the age group 14-16. No difference in estimated proportions between males and females was found. Unemployment (OR 3.13; CI 1.74-5.65) and migration background (OR 3.04; CI 2.12-4.36) were related to Internet addiction. This LCA-based study differentiated groups likely to have Internet addiction and at-risk use in the general population and provides characteristics to further define this rather new disorder. © 2013 S. Karger AG, Basel.

Variance Estimation, Design Effects, and Sample Size Calculations for Respondent-Driven Sampling

PubMed Central

2006-01-01

Hidden populations, such as injection drug users and sex workers, are central to a number of public health problems. However, because of the nature of these groups, it is difficult to collect accurate information about them, and this difficulty complicates disease prevention efforts. A recently developed statistical approach called respondent-driven sampling improves our ability to study hidden populations by allowing researchers to make unbiased estimates of the prevalence of certain traits in these populations. Yet, not enough is known about the sample-to-sample variability of these prevalence estimates. In this paper, we present a bootstrap method for constructing confidence intervals around respondent-driven sampling estimates and demonstrate in simulations that it outperforms the naive method currently in use. We also use simulations and real data to estimate the design effects for respondent-driven sampling in a number of situations. We conclude with practical advice about the power calculations that are needed to determine the appropriate sample size for a study using respondent-driven sampling. In general, we recommend a sample size twice as large as would be needed under simple random sampling. PMID:16937083

Detection of Genital HPV Infection Using Urine Samples: a Population Based Study in India.

PubMed

Sabeena, Sasidharanpillai; Bhat, Parvati; Kamath, Veena; Mathew, Mary; Aswathyraj, Sushama; Devadiga, Santhosha; Prabhu, Suresha; Hindol, Maity; Chameetachal, Akhil; Krishnan, Anjana; Arunkumar, Govindakarnavar

2016-01-01

Cervical cancer is the second commonest cancer among Indian women and its association with human papilloma virus (HPV) is well established. This preventable cancer accounts for the maximum number of cancer related deaths among rural Indian women. Unlike in developed countries there are no organized cervical cancer screening programmes in India due to lack of resources and manpower. To detect genital HPV infection using urine samples among asymptomatic rural women in the age group of 18-65 years. The study area chosen was Perdoor village in Udupi Taluk, Karnataka State and all the women in the age group of 18-65 years formed the study cohort. A cross sectional study was conducted by house visits and 1,305 women were enrolled in the study. After taking written informed consent a data sheet was filled and early stream random urine samples were collected, transported to a laboratory at 4OC and aliquoted. Samples were tested using nested HPV PCR with PGMY09/11 and GP5+/6+ primers. Positive cases were genotyped by sequence analysis. Study participants included 1,134 sexually active and 171 unmarried women with a mean age at marriage of 22.1 (SD=3.9) years. Study area showed high female literacy rate of 86.6%. Five urine samples tested positive for HPV DNA (0.4%). We found very low genital HPV infection rate among women from monogamous community. This is the first major population based study carried out among asymptomatic rural women to detect genital HPV infectio from Karnataka using urine samples.

Mapping the Risk of Snakebite in Sri Lanka - A National Survey with Geospatial Analysis.

PubMed

Ediriweera, Dileepa Senajith; Kasturiratne, Anuradhani; Pathmeswaran, Arunasalam; Gunawardena, Nipul Kithsiri; Wijayawickrama, Buddhika Asiri; Jayamanne, Shaluka Francis; Isbister, Geoffrey Kennedy; Dawson, Andrew; Giorgi, Emanuele; Diggle, Peter John; Lalloo, David Griffith; de Silva, Hithanadura Janaka

2016-07-01

There is a paucity of robust epidemiological data on snakebite, and data available from hospitals and localized or time-limited surveys have major limitations. No study has investigated the incidence of snakebite across a whole country. We undertook a community-based national survey and model based geostatistics to determine incidence, envenoming, mortality and geographical pattern of snakebite in Sri Lanka. The survey was designed to sample a population distributed equally among the nine provinces of the country. The number of data collection clusters was divided among districts in proportion to their population. Within districts clusters were randomly selected. Population based incidence of snakebite and significant envenoming were estimated. Model-based geostatistics was used to develop snakebite risk maps for Sri Lanka. 1118 of the total of 14022 GN divisions with a population of 165665 (0.8%of the country's population) were surveyed. The crude overall community incidence of snakebite, envenoming and mortality were 398 (95% CI: 356-441), 151 (130-173) and 2.3 (0.2-4.4) per 100000 population, respectively. Risk maps showed wide variation in incidence within the country, and snakebite hotspots and cold spots were determined by considering the probability of exceeding the national incidence. This study provides community based incidence rates of snakebite and envenoming for Sri Lanka. The within-country spatial variation of bites can inform healthcare decision making and highlights the limitations associated with estimates of incidence from hospital data or localized surveys. Our methods are replicable, and these models can be adapted to other geographic regions after re-estimating spatial covariance parameters for the particular region.

DNA motif alignment by evolving a population of Markov chains.

PubMed

Bi, Chengpeng

2009-01-30

Deciphering cis-regulatory elements or de novo motif-finding in genomes still remains elusive although much algorithmic effort has been expended. The Markov chain Monte Carlo (MCMC) method such as Gibbs motif samplers has been widely employed to solve the de novo motif-finding problem through sequence local alignment. Nonetheless, the MCMC-based motif samplers still suffer from local maxima like EM. Therefore, as a prerequisite for finding good local alignments, these motif algorithms are often independently run a multitude of times, but without information exchange between different chains. Hence it would be worth a new algorithm design enabling such information exchange. This paper presents a novel motif-finding algorithm by evolving a population of Markov chains with information exchange (PMC), each of which is initialized as a random alignment and run by the Metropolis-Hastings sampler (MHS). It is progressively updated through a series of local alignments stochastically sampled. Explicitly, the PMC motif algorithm performs stochastic sampling as specified by a population-based proposal distribution rather than individual ones, and adaptively evolves the population as a whole towards a global maximum. The alignment information exchange is accomplished by taking advantage of the pooled motif site distributions. A distinct method for running multiple independent Markov chains (IMC) without information exchange, or dubbed as the IMC motif algorithm, is also devised to compare with its PMC counterpart. Experimental studies demonstrate that the performance could be improved if pooled information were used to run a population of motif samplers. The new PMC algorithm was able to improve the convergence and outperformed other popular algorithms tested using simulated and biological motif sequences.

Web Intervention for Adolescents Affected by Disaster: Population-Based Randomized Controlled Trial.

PubMed

Ruggiero, Kenneth J; Price, Matthew; Adams, Zachary; Stauffacher, Kirstin; McCauley, Jenna; Danielson, Carla Kmett; Knapp, Rebecca; Hanson, Rochelle F; Davidson, Tatiana M; Amstadter, Ananda B; Carpenter, Matthew J; Saunders, Benjamin E; Kilpatrick, Dean G; Resnick, Heidi S

2015-09-01

To assess the efficacy of Bounce Back Now (BBN), a modular, Web-based intervention for disaster-affected adolescents and their parents. A population-based randomized controlled trial used address-based sampling to enroll 2,000 adolescents and parents from communities affected by tornadoes in Joplin, MO, and several areas in Alabama. Data collection via baseline and follow-up semi-structured telephone interviews was completed between September 2011 and August 2013. All families were invited to access the BBN study Web portal irrespective of mental health status at baseline. Families who accessed the Web portal were assigned randomly to 1 of 3 groups: BBN, which featured modules for adolescents and parents targeting adolescents' mental health symptoms; BBN plus additional modules targeting parents' mental health symptoms; or assessment only. The primary outcomes were adolescent symptoms of posttraumatic stress disorder (PTSD) and depression. Nearly 50% of families accessed the Web portal. Intent-to-treat analyses revealed time × condition interactions for PTSD symptoms (B = -0.24, SE = 0.08, p < .01) and depressive symptoms (B = -0.23, SE = 0.09, p < .01). Post hoc comparisons revealed fewer PTSD and depressive symptoms for adolescents in the experimental versus control conditions at 12-month follow-up (PTSD: B = -0.36, SE = 0.19, p = .06; depressive symptoms: B = -0.42, SE = 0.19, p = 0.03). A time × condition interaction also was found that favored the BBN versus BBN + parent self-help condition for PTSD symptoms (B = 0.30, SE = 0.12, p = .02) but not depressive symptoms (B = 0.12, SE = 0.12, p = .33). Results supported the feasibility and initial efficacy of BBN as a scalable disaster mental health intervention for adolescents. Technology-based solutions have tremendous potential value if found to reduce the mental health burden of disasters. Web-based Intervention for Disaster-Affected Youth and Families; http://clinicaltrials.gov; NCT01606514. Copyright © 2015 American Academy of Child and Adolescent Psychiatry. All rights reserved.

Prevalence and correlates of resistance training in a regional Australian population.

PubMed

Humphries, B; Duncan, M J; Mummery, W K

2010-07-01

The core components of physical activity, cardiovascular endurance, muscular strength, balance and flexibility can provide many health benefits and potentially slow declines associated with aging. Aerobic exercise message to the public has been widely promoted by national health authorities, although the promotion of resistance training has received far less attention. In this research, the prevalence of resistance training in a sample of adults living in regional Australia was primarily assessed. A computer-assisted telephone interview survey (n=1230) was conducted by the Population Research Laboratory at Central Queensland University on Queensland adults in October to November 2006. Respondents were asked to report the frequency with which they engaged in resistance training. Respondents were 18 years or older that could be contacted by direct-dialled, land-based telephone service. A telephone database using a computer program to select, with replacement, a simple random sample of phone numbers selected respondents. Almost 14% of the population did some form of gym-based resistance training in the week before the survey. There was a significant (p<0.05) reduction in participation levels with age. Participation was highest amongst the youngest 18-34-year-olds (23.8%), steadily declining with age to a low of 7% in the 55 years and older age group. There was no significant association between sexes and participation in resistance training. The findings underscore the need to increase overall education on the benefits of resistance training with an emphasis among targeted adult populations to increase participation in resistance training.

Bias of health estimates obtained from chronic disease and risk factor surveillance systems using telephone population surveys in Australia: results from a representative face-to-face survey in Australia from 2010 to 2013.

PubMed

Dal Grande, Eleonora; Chittleborough, Catherine R; Campostrini, Stefano; Taylor, Anne W

2016-04-18

Emerging communication technologies have had an impact on population-based telephone surveys worldwide. Our objective was to examine the potential biases of health estimates in South Australia, a state of Australia, obtained via current landline telephone survey methodologies and to report on the impact of mobile-only household on household surveys. Data from an annual multi-stage, systematic, clustered area, face-to-face population survey, Health Omnibus Survey (approximately 3000 interviews annually), included questions about telephone ownership to assess the population that were non-contactable by current telephone sampling methods (2006 to 2013). Univariable analyses (2010 to 2013) and trend analyses were conducted for sociodemographic and health indicator variables in relation to telephone status. Relative coverage biases (RCB) of two hypothetical telephone samples was undertaken by examining the prevalence estimates of health status and health risk behaviours (2010 to 2013): directory-listed numbers, consisting mainly of landline telephone numbers and a small proportion of mobile telephone numbers; and a random digit dialling (RDD) sample of landline telephone numbers which excludes mobile-only households. Telephone (landline and mobile) coverage in South Australia is very high (97%). Mobile telephone ownership increased slightly (7.4%), rising from 89.7% in 2006 to 96.3% in 2013; mobile-only households increased by 431% over the eight year period from 5.2% in 2006 to 27.6% in 2013. Only half of the households have either a mobile or landline number listed in the telephone directory. There were small differences in the prevalence estimates for current asthma, arthritis, diabetes and obesity between the hypothetical telephone samples and the overall sample. However, prevalence estimate for diabetes was slightly underestimated (RCB value of -0.077) in 2013. Mixed RCB results were found for having a mental health condition for both telephone samples. Current smoking prevalence was lower for both hypothetical telephone samples in absolute differences and RCB values: -0.136 to -0.191 for RDD landline samples and -0.129 to -0.313 for directory-listed samples. These findings suggest landline-based sampling frames used in Australia, when appropriately weighted, produce reliable representative estimates for some health indicators but not for all. Researchers need to be aware of their limitations and potential biased estimates.

The Type of Fat Ingested at Breakfast Influences the Plasma Lipid Profile of Postmenopausal Women

PubMed Central

Morillas-Ruiz, J. M.; Delgado-Alarcon, J. M.; Rubio-Perez, J. M.; Albaladejo Oton, M. D.

2014-01-01

To assess whether the type of fat ingested at breakfast can modify the plasma lipid profile and other cardiovascular risk variables in postmenopausal women at risk of cardiovascular disease, a longitudinal, randomized, and crossover study was carried out with postmenopausal women at risk of CVD. They were randomly assigned to eat each type of breakfast during one month: 6 study periods (breakfast with the same composition plus butter/margarine/virgin olive oil) separated by two washout periods. On the first and last days of each study period, weight, arterial blood pressure, heart rate, and body mass index were recorded in fasting conditions and a blood sample was collected to measure plasma lipid profile. When comparing final values to baseline values, we only found out statistically significant differences on plasma lipid profiles. Butter-based breakfast increased total cholesterol and HDL, while margarine-based breakfast decreased total cholesterol and LDL and increased HDL. After the olive oil-based breakfast intake, a tendency towards a decrease of total cholesterol and LDL levels and an increase of HDL levels was observed. No statistically significant differences were observed in triglycerides levels, BMI, and arterial pressure in any breakfast type. The margarine-based breakfast was the only one which significantly increased the percentage of volunteers with optimal lipid profiles. The polyunsaturated fat at breakfast has improved the plasma lipid profile in the analyzed sample population, suggesting that PUFA-based breakfast can be advisable in women at risk of CVD. PMID:25136625

Response rate differences between web and alternative data collection methods for public health research: a systematic review of the literature.

PubMed

Blumenberg, Cauane; Barros, Aluísio J D

2018-07-01

To systematically review the literature and compare response rates (RRs) of web surveys to alternative data collection methods in the context of epidemiologic and public health studies. We reviewed the literature using PubMed, LILACS, SciELO, WebSM, and Google Scholar databases. We selected epidemiologic and public health studies that considered the general population and used two parallel data collection methods, being one web-based. RR differences were analyzed using two-sample test of proportions, and pooled using random effects. We investigated agreement using Bland-and-Altman, and correlation using Pearson's coefficient. We selected 19 studies (nine randomized trials). The RR of the web-based data collection was 12.9 percentage points (p.p.) lower (95% CI = - 19.0, - 6.8) than the alternative methods, and 15.7 p.p. lower (95% CI = - 24.2, - 7.3) considering only randomized trials. Monetary incentives did not reduce the RR differences. A strong positive correlation (r = 0.83) between the RRs was observed. Web-based data collection present lower RRs compared to alternative methods. However, it is not recommended to interpret this as a meta-analytical evidence due to the high heterogeneity of the studies.

Design to monitor trend in abundance and presence of American beaver (Castor canadensis) at the national forest scale.

PubMed

Beck, Jeffrey L; Dauwalter, Daniel C; Gerow, Kenneth G; Hayward, Gregory D

2010-05-01

Wildlife conservationists design monitoring programs to assess population dynamics, project future population states, and evaluate the impacts of management actions on populations. Because agency mandates and conservation laws call for monitoring data to elicit management responses, it is imperative to design programs that match the administrative scale for which management decisions are made. We describe a program to monitor population trends in American beaver (Castor canadensis) on the US Department of Agriculture, Black Hills National Forest (BHNF) in southwestern South Dakota and northeastern Wyoming, USA. Beaver have been designated as a management indicator species on the BHNF because of their association with riparian and aquatic habitats and its status as a keystone species. We designed our program to monitor the density of beaver food caches (abundance) within sampling units with beaver and the proportion of sampling units with beavers present at the scale of a national forest. We designated watersheds as sampling units in a stratified random sampling design that we developed based on habitat modeling results. Habitat modeling indicated that the most suitable beaver habitat was near perennial water, near aspen (Populus tremuloides) and willow (Salix spp.), and in low gradient streams at lower elevations. Results from the initial monitoring period in October 2007 allowed us to assess costs and logistical considerations, validate our habitat model, and conduct power analyses to assess whether our sampling design could detect the level of declines in beaver stated in the monitoring objectives. Beaver food caches were located in 20 of 52 sampled watersheds. Monitoring 20 to 25 watersheds with beaver should provide sufficient power to detect 15-40% declines in the beaver food cache index as well as a twofold decline in the odds of beaver being present in watersheds. Indices of abundance, such as the beaver food cache index, provide a practical measure of population status to conduct long-term monitoring across broad landscapes such as national forests.

A Systematic Review of Rural, Theory-based Physical Activity Interventions.

PubMed

Walsh, Shana M; Meyer, M Renée Umstattd; Gamble, Abigail; Patterson, Megan S; Moore, Justin B

2017-05-01

This systematic review synthesized the scientific literature on theory-based physical activity (PA) interventions in rural populations. PubMed, PsycINFO, and Web of Science databases were searched to identify studies with a rural study sample, PA as a primary outcome, use of a behavioral theory or model, randomized or quasi-experimental research design, and application at the primary and/or secondary level of prevention. Thirty-one studies met our inclusion criteria. The Social Cognitive Theory (N = 14) and Transtheoretical Model (N = 10) were the most frequently identified theories; however, most intervention studies were informed by theory but lacked higher-level theoretical application and testing. Interventions largely took place in schools (N = 10) and with female-only samples (N = 8). Findings demonstrated that theory-based PA interventions are mostly successful at increasing PA in rural populations but require improvement. Future studies should incorporate higher levels of theoretical application, and should explore adapting or developing rural-specific theories. Study designs should employ more rigorous research methods to decrease bias and increase validity of findings. Follow-up assessments to determine behavioral maintenance and/or intervention sustainability are warranted. Finally, funding agencies and journals are encouraged to adopt rural-urban commuting area codes as the standard for defining rural.

Prevalence of metabolic syndrome and its association with educational inequalities among Brazilian adults: a population-based study.

PubMed

Gronner, M F; Bosi, P L; Carvalho, A M; Casale, G; Contrera, D; Pereira, M A; Diogo, T M; Torquato, M T C G; Souza, G M D; Oishi, J; Leal, A M O

2011-07-01

The present study estimated the prevalence of metabolic syndrome (MS) according to the criteria established by the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATPIII) and the International Diabetes Federation (IDF) and analyzed the contribution of social factors in an adult urban population in the Southeastern region of Brazil. The sample plan was based on multistage probability sampling according to family head income and educational level. A random sample of 1116 subjects aged 30 to 79 years was studied. Participants answered a questionnaire about socio-demographic variables and medical history. Fasting capillary glucose (FCG), total cholesterol, high-density lipoprotein cholesterol (HDL-C), and triglycerides were determined and all non-diabetic subjects were submitted to the 75-g oral glucose tolerance test. Body mass index (BMI, kg/m(2)), waist circumference and blood pressure (BP) were determined. Age- and gender-adjusted prevalence of MS was 35.9 and 43.2% according to NCEP-ATPIII and IDF criteria, respectively. Substantial agreement was found between NCEP-ATPIII and IDF definitions. Low HDL-C levels and high BP were the most prevalent MS components according to NCEP-ATPIII criteria (76.3 and 59.2%, respectively). Considering the diagnostic criteria adopted, 13.5% of the subjects had diabetes and 9.7% had FCG ≥100 mg/dL. MS prevalence was significantly associated with age, skin color, BMI, and educational level. This cross-sectional population-based study in the Southeastern region of Brazil indicates that MS is highly prevalent and associated with an important social indicator, i.e., educational level. This result suggests that in developing countries health policy planning to reduce the risk of MS, in particular, should consider improvement in education.

45 CFR 5b.11 - Exempt systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Random Samples of the U.S. Population; (B) The Health Manpower Inventories and Surveys; (C) The Vital... is exempt under subsection (k)(2) of the Act and the individual has been, as a result of the...

45 CFR 5b.11 - Exempt systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Random Samples of the U.S. Population; (B) The Health Manpower Inventories and Surveys; (C) The Vital... is exempt under subsection (k)(2) of the Act and the individual has been, as a result of the...

45 CFR 5b.11 - Exempt systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Surveys Conduct in Random Samples of the U.S. Population; (B) The Health Manpower Inventories and Surveys... is exempt under subsection (k)(2) of the Act and the individual has been, as a result of the...

Multiple Comparisons of Observation Means--Are the Means Significantly Different?

ERIC Educational Resources Information Center

Fahidy, T. Z.

2009-01-01

Several currently popular methods of ascertaining which treatment (population) means are different, via random samples obtained under each treatment, are briefly described and illustrated by evaluating catalyst performance in a chemical reactor.

The role of patient activation in frequent attendance at primary care: a population-based study of people with chronic disease.

PubMed

Donald, Maria; Ware, Robert S; Ozolins, Ieva Z; Begum, Nelufa; Crowther, Ruth; Bain, Christopher

2011-05-01

This study explores a range of relevant socio-demographic, physical and psychological factors in a unique examination of the risk factors for frequent attendance at primary care. The impact of patient activation for self-management on health service utilisation is of particular interest. A population-based sample of people with chronic disease from Queensland, Australia, was interviewed using computer assisted telephone surveying. Data were collected from a random sample of 1470 people with either diabetes or a cardiovascular condition. As participants became more activated they were less likely to frequently attend their main health care provider for assistance with their chronic condition. For both conditions the association was graduated and for participants with a cardiovascular condition this association remained statistically significant even after controlling for other potentially influential factors such as disease severity, length of time since diagnosis, and psychological distress. Characteristics of the individual, including patient activation and psychological functioning, as well as disease factors contribute to primary care consulting patterns among people with chronic illness. Efforts to improve patient activation for self-management should remain a central element of chronic care. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Examining the Cervical Screening Behaviour of Women Aged 50 or above and Its Predicting Factors: A Population-Based Survey.

PubMed

Chan, Carmen W H; Choi, Kai Chow; Wong, Rosa S; Chow, Ka Ming; So, Winnie K W; Leung, Doris Y P; Lam, Wendy W T; Goggins, William

2016-12-02

Under-screening may increase the risk of cervical cancer in middle-aged women. This study aimed to investigate cervical cancer screening behaviour and its predictors among women aged 50 years or above. A population-based sample of 959 women was recruited by telephone from domestic households in Hong Kong, using random methods, and a structured questionnaire developed to survey participants. Multivariable logistic regressions were performed to examine the factors independently associated with cervical screening behaviour. Nearly half the sample (48%) had never had a cervical smear test. Multivariable analyses showed that age, educational level, marital status, family history of cancer, smoking status, use of complementary therapy, recommendation from health professionals, and believing that regular visits to a doctor or a Chinese herbalist were good for their health were predictors of cervical screening behaviour. Misconceptions concerned with menopause may reduce women's perceived susceptibility to cervical cancer, especially if they are 50 or above, and exert a negative effect on their screening behaviour. Healthcare professionals should actively approach these high-risk groups-older unmarried women, smokers, those less educated and who are generally not much concerned with their health.

[Design requirements for clinical trials on re-evaluation of safety and efficacy of post-marketed Chinese herbs].

PubMed

Xie, Yanming; Wei, Xu

2011-10-01

Re-evaluation of post-marketed based on pharmacoepidemiology is to study and collect clinical medicine safety in large population under practical applications for a long time. It is necessary to conduct re-evaluation of clinical effectiveness because of particularity of traditional Chinese medicine (TCM). Right before carrying out clinical trials on re-evaluation of post-marketed TCM, we should determine the objective of the study and progress it in the assessment mode of combination of disease and syndrome. Specical population, involving children and seniors who were excluded in pre-marketed clinical trial, were brought into drug monitoring. Sample size needs to comply with statistical requirement. We commonly use cohort study, case-control study, nested case-control, pragmatic randomized controlled trials.

Evaluation of a sexual health approach to prevent HIV among low income, urban, primarily African American women: results of a randomized controlled trial.

PubMed

Robinson, Beatrice Bean E; Uhl, Gary; Miner, Michael; Bockting, Walter O; Scheltema, Karen E; Rosser, B R Simon; Westover, Bonita

2002-06-01

This randomized controlled trial evaluated an innovative culturally specific sexual health intervention-targeting, but not limited to, low-income African American women-in which HIV and sexually transmitted disease prevention strategies were combined with comprehensive sexuality education. The intervention was delivered and evaluated in community-based settings to 218 participants randomly assigned to treatment or a no-treatment control group. Participants were interviewed at pretest and 3 and 9 months after the intervention to assess changes in both sexuality and HIV risk variables. The intervention was effective in improving sexual anatomy knowledge at both 3- and 9-month follow-up. For a subset of women engaging in unprotected sex at pretest, the intervention group reported an increase in positive attitudes toward the female condom at 9-month follow-up. Reasons for the weak treatment effect are discussed in the context of challenges inherent in conducting community-based research with high-risk populations and sensitive topics. Recommendations are provided for improving sample attrition, statistical power, and response bias and for altering the intervention so as to strengthen its impact.

A population-based survey of prevalence of diabetes and correlates in an urban slum community in Nairobi, Kenya.

PubMed

Ayah, Richard; Joshi, Mark D; Wanjiru, Rosemary; Njau, Elijah K; Otieno, C Fredrick; Njeru, Erastus K; Mutai, Kenneth K

2013-04-20

Urban slum populations in Africa continue to grow faster than national populations. Health strategies that focus on non-communicable diseases (NCD) in this segment of the population are generally lacking. We determined the prevalence of diabetes and associated cardiovascular disease (CVD) risk factors correlates in Kibera, Nairobi's largest slum. We conducted a population-based household survey utilising cluster sampling with probability proportional to size. Households were selected using a random walk method and consenting residents aged 18 years and above were recruited. The WHO STEPS instrument was administered. A random capillary blood sugar (RCBS) was obtained; known persons with diabetes and subjects with a RCBS >11.1 had an 8 hours fasting blood sugar (FBS) drawn. Diabetes was defined as a RCBS of  ≥ 11.1 mmol/l and a FBS of  ≥ 7.0 mmol/l, or a prior diagnosis or receiving diabetes drug treatment. Out of 2061 enrolled; 50.9% were males, mean age was 33.4 years and 87% had a minimum of primary education. Only 10.6% had ever had a blood sugar measurement. Age adjusted prevalence of diabetes was 5.3% (95% CI 4.2-6.4) and prevalence increased with age peaking at 10.5% (95% CI 6.8-14.3%) in the 45-54 year age category. Diabetes mellitus (DM) correlates were: 13.1% smoking, 74.9% alcohol consumption, 75.7% high level of physical activity; 16.3% obese and 29% overweight with higher rates in women.Among persons with diabetes the odds of obesity, elevated waist circumference and hypertension were three, two and three fold respectively compared to those without diabetes. Cardiovascular risk factors among subjects with diabetes were high and mirrored that of the entire sample; however they had a significantly higher use of tobacco. This previously unstudied urban slum has a high prevalence of DM yet low screening rates. Key correlates include cigarette smoking and high alcohol consumption. However high levels of physical activity were also reported. Findings have important implications for NCD prevention and care. For this rapidly growing youthful urban slum population policy makers need to focus their attention on strategies that address not just communicable diseases but non communicable diseases as well.

How to infer relative fitness from a sample of genomic sequences.

PubMed

Dayarian, Adel; Shraiman, Boris I

2014-07-01

Mounting evidence suggests that natural populations can harbor extensive fitness diversity with numerous genomic loci under selection. It is also known that genealogical trees for populations under selection are quantifiably different from those expected under neutral evolution and described statistically by Kingman's coalescent. While differences in the statistical structure of genealogies have long been used as a test for the presence of selection, the full extent of the information that they contain has not been exploited. Here we demonstrate that the shape of the reconstructed genealogical tree for a moderately large number of random genomic samples taken from a fitness diverse, but otherwise unstructured, asexual population can be used to predict the relative fitness of individuals within the sample. To achieve this we define a heuristic algorithm, which we test in silico, using simulations of a Wright-Fisher model for a realistic range of mutation rates and selection strength. Our inferred fitness ranking is based on a linear discriminator that identifies rapidly coalescing lineages in the reconstructed tree. Inferred fitness ranking correlates strongly with actual fitness, with a genome in the top 10% ranked being in the top 20% fittest with false discovery rate of 0.1-0.3, depending on the mutation/selection parameters. The ranking also enables us to predict the genotypes that future populations inherit from the present one. While the inference accuracy increases monotonically with sample size, samples of 200 nearly saturate the performance. We propose that our approach can be used for inferring relative fitness of genomes obtained in single-cell sequencing of tumors and in monitoring viral outbreaks. Copyright © 2014 by the Genetics Society of America.

Job strain and blood pressure in employed men and women: a pooled analysis of four northern italian population samples.

PubMed

Cesana, Giancarlo; Sega, Roberto; Ferrario, Marco; Chiodini, Paolo; Corrao, Giovanni; Mancia, Giuseppe

2003-01-01

The extent to which psychosocial stress concurs to raise blood pressure is still uncertain. Here the association between job strain and office blood pressure in a pooled analysis of four population samples from northern Italy is assessed. Four surveys assessing prevalence of major coronary risk factors were performed in 1986, 1990, 1991, and 1993 in area "Brianza" (Milan), a World Health Organization-MONItoring cardiovascular disease (WHO-MONICA) Project collaborating center. Ten year age- and gender-stratified independent samples were randomly recruited from the 25- to 64-year-old residents. The methods used to assess coronary risk factors strictly adhered to the MONICA manual, were kept constant, and underwent internal and external quality controls. Job strain was investigated through the administration to employed participants of a questionnaire derived from the Karasek model, assessing job demand/control latitude. Analysis was restricted to 25- to 54-year-old participants, untreated for hypertension (1799 men and 1010 women). Among men, there was a 3 mm Hg increase of systolic blood pressure (p<.001) moving from low to high strain job categories. This difference was independent from age, education, body mass index, alcohol intake, smoking habits, leisure time physical activity, and survey. No relevant differences among job strain categories were found in women and for diastolic blood pressure in both gender groups. These results carried out on a large population-based sample confirm previous findings obtained adopting ambulatory blood pressure measurements in more restricted samples of population or patients. Further research is needed to clarify the relationship between perceived work stress and blood pressure in women.

Detection of Celiac Disease and Lymphocytic Enteropathy by Parallel Serology and Histopathology in a Population-Based Study

PubMed Central

Walker, Marjorie M.; Murray, Joseph A.; Ronkainen, Jukka; Aro, Pertti; Storskrubb, Tom; D’Amato, Mauro; Lahr, Brian; Talley, Nicholas J.; Agreus, Lars

2010-01-01

Background & Aims Although serological analysis is used in diagnosis of celiac disease, histopathology is considered most reliable. We performed a prospective study to determine the clinical, pathological and serological spectrum of celiac disease in a general population (Kalixanda study). Methods A random sample of an adult general population (n=1000) was analyzed by upper endoscopy, duodenal biopsy, and serological analysis of tissue transglutaminase (tTg) levels; endomysial antibody (EMA) levels were analyzed in samples that were tTg+. The cutoff values for diagnosis of celiac disease were villous atrophy with 40 intraepithelial lymphocytes (IELs)/100 enterocytes (ECs). Results Samples from 33 subjects were tTg+ and 16 were EMA+. Histological analysis identified 7/1000 subjects (0.7%) with celiac disease; all were tTg+ and 6/7 were EMA+. Another 26 subjects were tTg+ (7/26 EMA+). This was addressed by a second quantitative pathology study, (nested case-control design) using a threshold of 25 IELS/100 ECs. In this analysis, all 13 samples that were tTg+ and EMA+ had ≥25 IELs/100ECs. In total, 16 subjects (1.6%) had serological and histological evidence of gluten-sensitive enteropathy. IELs were quantified in duodenal biopsy samples from seronegative individuals (n=500); 19 (3.8%) had >25 IELs and lymphocytic duodenosis (LD). Conclusions Measurement of ≥25 IELs/100 ECs correlated with serological indicators of celiac disease; a higher IEL threshold could miss 50% of cases. Quantification of tTg is a sensitive test for celiac disease; diagnosis can be confirmed by observation of ≥25 IELs/100ECs in duodenal biopsies. Lymphocytic enteropathy (celiac disease and LD) is common in the population (5.4%). PMID:20398668

Chemical classification of iron meteorites. XI. Multi-element studies of 38 new irons and the high abundance of ungrouped irons from Antarctica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wasson, J.T.; Ouyang, Xinwei; Wang, Jianmin

1989-03-01

The authors report concentrations of 14 elements in the metal of 38 iron meteorites and a pallasite. The meteorites are classified based on these data and on structural observations. Three samples are paired with previously classified irons; thus, these additional 35 irons raise the number of well-classified, independent iron meteorites to 598. One Yamato iron contains 342 mg/g Ni, the second highest Ni content in an IAB iron after Oktibbeha County. Two small irons from Western Australia appear to be metal nodules from mesosiderites. Several of the new irons are from Antarctica. Of 24 independent irons from Antarctica, 8 aremore » ungrouped. The fraction, 0.333, is much higher than the fraction 0.161 among all 598 classified irons. Statistical tests show that it is highly improbably ({approximately}2.9% probability) that the Antarctic population is a random sample of the larger population. The difference is probably related to the fact that the median mass of Antarctic irons is about two orders of magnitude smaller than that of non-Antarctic irons. It is doubtful that the difference results from fragmentation patterns yielding different size distributions favoring smaller masses among ungrouped irons. More likely is the possibility that smaller meteoroids tend to sample a larger number of asteroidal source regions, perhaps because small meteoroids tend to have higher ejection velocities or because small meteoroids have random-walked a greater increment of orbital semimajor axis away from that of the parent body.« less

Cross sectional survey of perpetrators, victims, and witnesses of violence in Bogotá, Colombia

PubMed Central

Duque, L; Klevens, J; Ramirez, C

2003-01-01

Objectives: To establish the prevalence and distribution of witnesses, victims, and perpetrators of different types of violence in the general population and the proportion of victims consulting health services or reporting the incident to authorities. Methods: Cross sectional survey of a random sample of 3007 inhabitants between the ages of 15 and 60 in the city of Bogotá, Colombia, in 1997, based on a face to face interview. Results: Age adjusted past year prevalence of witnesses, victims, and perpetrators of physical aggression was 61%, 27%, and 27%, respectively, while lifetime prevalence of witnesses, victims, and perpetrators of assault with a weapon in this population reached 70%, 55%, and 5.8%. Between 11% and 67% of the victims consulted a health service and less than 32% reported the incident to an authority. Those involved in most types of physical violence tended to be young, male, from lower middle social classes, with some degree of secondary education, and single or divorced. Conclusions: Prevalence of witnesses and victims of violence in this sample appears to be high, while perpetrators constitute a small proportion. Violence is not equally distributed throughout the population suggesting the possibility of identifying a population at higher risk for the development of intervention programmes. PMID:12700220

Reinforcing Sampling Distributions through a Randomization-Based Activity for Introducing ANOVA

ERIC Educational Resources Information Center

Taylor, Laura; Doehler, Kirsten

2015-01-01

This paper examines the use of a randomization-based activity to introduce the ANOVA F-test to students. The two main goals of this activity are to successfully teach students to comprehend ANOVA F-tests and to increase student comprehension of sampling distributions. Four sections of students in an advanced introductory statistics course…

Natural history of heartburn: a 10-year population-based study.

PubMed

Olafsdottir, Linda Bjork; Gudjonsson, Hallgrimur; Jonsdottir, Heidur Hrund; Thjodleifsson, Bjarni

2011-02-07

To study the natural history and prevalence of heartburn at a 10-year interval, and to study the effect of heartburn on various symptoms and activities. A population-based postal study was carried out. Questionnaires were mailed to the same age- and gender-stratified random sample of the Icelandic population (aged 18-75 years) in 1996 and again in 2006. Subjects were classified with heartburn if they reported heartburn in the preceding year and/or week, based on the definition of heartburn. Heartburn in the preceding year was reported in 42.8% (1996) and 44.2% (2006) of subjects, with a strong relationship between those who experienced heartburn in both years. Heartburn in the preceding week was diagnosed in 20.8%. There was a significant relationship between heartburn, dyspepsia and irritable bowel syndrome. Individuals with a body mass index (BMI) below or higher than normal weight were more likely to have heartburn. Heartburn caused by food or beverages was reported very often by 20.0% of subjects. Heartburn is a common and chronic condition. Subjects with a BMI below or higher than normal weight are more likely to experience heartburn. Heartburn has a great impact on daily activities, sleep and quality of life.

Demythologizing sex education in Oklahoma: an attitudinal study.

PubMed

Turner, N H

1983-08-01

A randomized study was conducted to determine the distribution of attitudes among Oklahomans of voting age toward sex education and to analyze the relationship of demographic, sociocultural, and attitudinal factors. The state was stratified into six regions. Forty-five percent of the sample lived in urban areas, and 55% in rural areas. Random digit dialing and random selection within households were utilized to ensure a representative sample of the population. Eighty percent of the sample was found to be favorable toward sex education in the public schools, while 20% was unfavorable. A majority of respondents in all religious groups including "fundamentalists" were favorable. Seventeen variables were found to be significant in the univariate analysis of the data; eight were not significant. In a multivariate analysis, three variables, age, Protestant denominational type and female employment, were shown to have predictive ability in determining favorability and unfavorability. Implications for building community support for sex education also are discussed.

The Coalescent Process in Models with Selection

PubMed Central

Kaplan, N. L.; Darden, T.; Hudson, R. R.

1988-01-01

Statistical properties of the process describing the genealogical history of a random sample of genes are obtained for a class of population genetics models with selection. For models with selection, in contrast to models without selection, the distribution of this process, the coalescent process, depends on the distribution of the frequencies of alleles in the ancestral generations. If the ancestral frequency process can be approximated by a diffusion, then the mean and the variance of the number of segregating sites due to selectively neutral mutations in random samples can be numerically calculated. The calculations are greatly simplified if the frequencies of the alleles are tightly regulated. If the mutation rates between alleles maintained by balancing selection are low, then the number of selectively neutral segregating sites in a random sample of genes is expected to substantially exceed the number predicted under a neutral model. PMID:3066685

Emotional, Social, Educational Adjustment of Higher Secondary School Students in Relation to Academic Achievement

ERIC Educational Resources Information Center

Sekar, J. Master Arul; Lawrence, A.S. Arul

2016-01-01

The present study aims to investigate whether there is any significant relationship between adjustment and academic achievement of higher secondary school students. In this survey study, the investigators used stratified random sampling technique for selecting the sample from the population. The stratification was done on the basis of gender and…

Strategies for Coping with the Challenges of Incarceration among Nigerian Prison Inmates

ERIC Educational Resources Information Center

Agbakwuru, Chikwe; Awujo, Grace C.

2016-01-01

This paper investigated the strategies for coping with the challenges of incarceration among inmates of Port Harcourt Prison, Nigeria. The population was 2,997 inmates of the prison while the sample was 250 inmates drawn through stratified random sampling technique from the same Port Harcourt prison. Six research questions were posed and data for…

How Generalizable Is Your Experiment? An Index for Comparing Samples and Populations

ERIC Educational Resources Information Center

Tipton, Elizabeth

2013-01-01

Recent research on the design of social experiments has highlighted the effects of different design choices on research findings. Since experiments rarely collect their samples using random selection, in order to address these external validity problems and design choices, recent research has focused on two areas. The first area is on methods for…

Paradoxes in Film Ratings

ERIC Educational Resources Information Center

Moore, Thomas L.

2006-01-01

The author selected a simple random sample of 100 movies from the "Movie and Video Guide" (1996), by Leonard Maltin. The author's intent was to obtain some basic information on the population of roughly 19,000 movies through a small sample. The "Movie and Video Guide" by Leonard Maltin is an annual ratings guide to movies. While not all films ever…

Construct Equivalence of a National Certification Examination that Uses Dual Languages and Audio Assistant.

ERIC Educational Resources Information Center

Wang, Shudong; Wang, Ning; Hoadley, David

This study examined the comparability of scores on the National Nurses Aides Assessment Program (NNAAP) test across language and administration condition groups for calibration and validation samples that were randomly drawn from the same population. A sample of 20,568 candidate responses to 1 test form was used. This examination is given in…

Testing aerially applied Orthene for control of larch casebearer.

Treesearch

John S. Hard; Stanley Meso; Michael Haskett

1979-01-01

Orthene was tested in a randomized block experiment to determine efficacy against larch casebearer. Needlemining larval populations were sprayed in September 1976 by helicopter with 0.5 lb Orthene/gal water/acre (560 g a.i/9.3 l/ha). Spray deposit was sampled with Kromekote cards. Plot mean larval populations, spray deposit, and defoliation index were analyzed to...

Urban forest structure, ecosystem services and change in Syracuse, NY

Treesearch

David J. Nowak; Robert E. Hoehn; Allison R. Bodine; Eric J. Greenfield; Jarlath O' Neil-Dunne

2013-01-01

The tree population within the City of Syracuse was assessed using a random sampling of plots in 1999, 2001 and 2009 to determine how the population and the ecosystem services these trees provide have changed over time. Ecosystem services and values for carbon sequestration, air pollution removal and changes in building energy use were derived using the i-Tree Eco...

Efficient mitigation strategies for epidemics in rural regions.

PubMed

Scoglio, Caterina; Schumm, Walter; Schumm, Phillip; Easton, Todd; Roy Chowdhury, Sohini; Sydney, Ali; Youssef, Mina

2010-07-13

Containing an epidemic at its origin is the most desirable mitigation. Epidemics have often originated in rural areas, with rural communities among the first affected. Disease dynamics in rural regions have received limited attention, and results of general studies cannot be directly applied since population densities and human mobility factors are very different in rural regions from those in cities. We create a network model of a rural community in Kansas, USA, by collecting data on the contact patterns and computing rates of contact among a sampled population. We model the impact of different mitigation strategies detecting closely connected groups of people and frequently visited locations. Within those groups and locations, we compare the effectiveness of random and targeted vaccinations using a Susceptible-Exposed-Infected-Recovered compartmental model on the contact network. Our simulations show that the targeted vaccinations of only 10% of the sampled population reduced the size of the epidemic by 34.5%. Additionally, if 10% of the population visiting one of the most popular locations is randomly vaccinated, the epidemic size is reduced by 19%. Our results suggest a new implementation of a highly effective strategy for targeted vaccinations through the use of popular locations in rural communities.

Prevalence of isolated non-albumin proteinuria in the US population tested for both, urine total protein and urine albumin: An unexpected discovery.

PubMed

Katayev, Alexander; Zebelman, Arthur M; Sharp, Thomas M; Samantha Flynn; Bernstein, Richard K

2017-04-01

Isolated non-albumin proteinuria (NAP) is a condition when urine total protein concentrations are elevated without elevation of urine albumin. The prevalence of NAP in the US population tested for both, urine total protein and albumin was assessed in this study. The database of a US nationwide laboratory network was queried for test results when random urine albumin was ordered together with urine total protein and also when timed 24-hour urine albumin was ordered together with urine total protein. The total prevalence of NAP in the US population tested for both, urine total protein and albumin was calculated for patient groups having normal and low-normal urine albumin (random and timed) with elevated and severely increased urine total protein (random and timed). Also, the prevalence of NAP was calculated for patients with normal urine albumin to assess the probability of missing proteinuria if only urine albumin is measured. The prevalence of NAP in the random samples group was 10.1% (15.2% for females and 4.7% for males). Among patients with normal random albumin, there were 20.0% (27.3% of females and 10.7% of males) patients with NAP. The prevalence of NAP in the timed samples group was 24.6% (29.8% for females and 18.5% for males). Among patients with normal timed urine albumin, there were 36.2% (40.0% of females and 30.8% of males) patients with NAP. There was a strong positive association with female gender and NAP in most patients groups. Testing for only urine (micro)albumin can miss up to 40% of females and 30.8% of males with gross proteinuria. Copyright © 2016 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Mental illness in metropolitan, urban and rural Georgia populations

PubMed Central

2013-01-01

Background Mental illness represents an important public health problem. Local-level data concerning mental illness in different populations (e.g., socio-demographics and residence – metropolitan/urban/rural) provides the evidence-base for public health authorities to plan, implement and evaluate control programs. This paper describes prevalence and covariates of psychiatric conditions in Georgia populations in three defined geographic areas. Methods Data came from the Georgia population-based random-digit-dialing study investigating unwellness and chronic fatigue syndrome (CFS) in Georgia populations of three defined geographic areas (metropolitan, urban, and rural). Respondents were screened for symptoms of fatigue, sleep, cognition, and pain at household screening interviews, and a randomly selected sample completed detailed individual phone interviews. Based on the detailed phone interviews, we conducted one-day clinical evaluations of 292 detailed interview participants classified as unwell with a probable CFS (i.e. CFS-like; a functional somatic syndrome), 268 classified as other unwell, and 223 well (matched to CFS-like). Clinical evaluation included psychiatric classification by means of the Structured Clinical Interview for DSM (SCID). To derive prevalence estimates we used sample weighting to account for the complexity of the multistage sampling design. We used 2- and 3-way table analyses to examine socio-demographic and urbanicity specific associations and multiple logistic regression to calculate adjusted odds ratios. Results Anxiety and mood disorders were the most common psychiatric conditions. Nineteen percent of participants suffered a current anxiety disorder, 18% a mood disorder and 10% had two or more conditions. There was a significant linear trend in occurrence of anxiety or mood disorders from well to CFS-like. The most common anxiety disorders were post-traumatic stress disorder (PTSD) (6.6%) and generalized anxiety disorder (GAD) (5.8%). Logistic regression showed that lower education and female sex contributed significantly to risk for both PTSD and GAD. In addition, rural/urban residence and Hispanic ethnicity were associated with PTSD. We defined moderate to severe depression as Major Depressive Disorder or a Zung score >60 and logistic regression found lower education to be significantly associated but sex, age and urbanicity were not. Conclusions Overall occurrence of anxiety and mood disorders in Georgia mirrored national findings. However, PTSD and GAD occurred at twice the published national rates (3.6 and 2.7%, respectively). State and local prevalence and associations with education, sex and urbanicity comprise important considerations for developing control programs. The increased prevalence of anxiety and mood disorders in people with a functional somatic syndrome (or CFS-like illness) is important for primary care providers, who should consider additional psychiatric screening or referral of individuals presenting with somatoform symptoms. PMID:23631737

Prevalence of vitamin D deficiency and its associated factors among the urban elderly population in Hyderabad metropolitan city, South India.

PubMed

Suryanarayana, Palla; Arlappa, Nimmathota; Sai Santhosh, Vadakattu; Balakrishna, Nagalla; Lakshmi Rajkumar, Pondey; Prasad, Undrajavarapu; Raju, Banavath Bhoja; Shivakeseva, Kommula; Divya Shoshanni, Kondru; Seshacharyulu, Madabushi; Geddam, Jagjeevan Babu; Prasanthi, Prabhakaran Sobhana; Ananthan, Rajendran

2018-03-01

Deficiency of vitamin D has been associated with various health conditions. However, vitamin D deficiency (VDD) and factors associated with VDD are not well studied, especially among the urban elderly population of India. To assess the prevalence of VDD and its associated factors among the urban free-living elderly population in Hyderabad. A community-based cross-sectional study was conducted among 298 urban elderly (≥60 years) by adapting a random sampling procedure. Demographic particulars were collected. Blood pressure and anthropometric measurements were recorded using standard equipment. Fasting glucose, lipid profile and 25-hydroxy vitamin D [25(OH) D] were estimated in plasma samples. The mean ± SE plasma vitamin D and the prevalence of VDD among the urban elderly population were 19.3 ± 0.54 (ng/ml) and 56.3%, respectively. The prevalence of VDD was significantly associated with education, high body mass index (BMI), hypertension (HT) and metabolic syndrome (MS). Multiple logistic regression analysis revealed HT as a significant predictor of vitamin D deficiency and the risk of VDD was double among the elderly with hypertension. The prevalence of VDD was high among the urban elderly population in the south Indian city of Hyderabad. High BMI, MS, HT and education are significant associated factors of VDD.

Cluster-Randomized Trial to Increase Hepatitis B Testing among Koreans in Los Angeles.

PubMed

Bastani, Roshan; Glenn, Beth A; Maxwell, Annette E; Jo, Angela M; Herrmann, Alison K; Crespi, Catherine M; Wong, Weng K; Chang, L Cindy; Stewart, Susan L; Nguyen, Tung T; Chen, Moon S; Taylor, Victoria M

2015-09-01

In the United States, Korean immigrants experience a disproportionately high burden of chronic hepatitis B (HBV) viral infection and associated liver cancer compared with the general population. However, despite clear clinical guidelines, HBV serologic testing among Koreans remains persistently suboptimal. We conducted a cluster-randomized trial to evaluate a church-based small group intervention to improve HBV testing among Koreans in Los Angeles. Fifty-two Korean churches, stratified by size (small, medium, large) and location (Koreatown versus other), were randomized to intervention or control conditions. Intervention church participants attended a single-session small-group discussion on liver cancer and HBV testing, and control church participants attended a similar session on physical activity and nutrition. Outcome data consisted of self-reported HBV testing obtained via 6-month telephone follow-up interviews. We recruited 1,123 individuals, 18 to 64 years of age, across the 52 churches. Ninety-two percent of the sample attended the assigned intervention session and 86% completed the 6-month follow-up. Sample characteristics included were as follows: mean age 46 years, 65% female, 97% born in Korea, 69% completed some college, and 43% insured. In an intent-to-treat analysis, the intervention produced a statistically significant effect (OR = 4.9, P < 0.001), with 19% of intervention and 6% of control group participants reporting a HBV test. Our intervention was successful in achieving a large and robust effect in a population at high risk of HBV infection and sequelae. The intervention was fairly resource efficient and thus has high potential for replication in other high-risk Asian groups. ©2015 American Association for Cancer Research.

Features in grocery stores that motivate shoppers to buy healthier foods, ConsumerStyles 2014

PubMed Central

Moore, Latetia V; Pinard, Courtney A.; Yaroch, Amy L.

2016-01-01

Objective We examined nine features in grocery stores shoppers reported motivated them to purchase more healthful foods in the past month. Design Features were compiled from common supermarket practices for each of the 4 Ps of marketing: pricing, placement, promotion, and product. We examined percentages of the features overall and by shopping frequency using chi-square tests from a 2014 cross sectional web-based health attitudes and behaviors survey, ConsumerStyles. The survey was fielded from June to July in 2014. Setting Participants were part of a market research consumer panel that were randomly recruited by probability-based sampling using address-based sampling methods to achieve a sample representative of the U.S. population. Subjects Data from 4,242 adults ages 18 and older were analyzed. Results About 44% of respondents indicated at least one feature motivated them to purchase more healthful foods. Top choices included in-store coupons or specials (20.1%), availability of convenient, ready-to-eat more healthful foods (18.8%), product labels or advertising on packages (15.2%), and labels or signs on shelves that highlighted more healthful options (14.6%). Frequent shoppers reported being motivated to purchase more healthful foods by in-store tastings/recipe demonstrations and coupons/specials more often than infrequent shoppers. Conclusions Enhancing the visibility and appeal of more healthful food items in grocery stores may help improve dietary choices in some populations but additional research is needed to identify the most effective strategies for interventions. PMID:26831484

Genealogical Properties of Subsamples in Highly Fecund Populations

NASA Astrophysics Data System (ADS)

Eldon, Bjarki; Freund, Fabian

2018-03-01

We consider some genealogical properties of nested samples. The complete sample is assumed to have been drawn from a natural population characterised by high fecundity and sweepstakes reproduction (abbreviated HFSR). The random gene genealogies of the samples are—due to our assumption of HFSR—modelled by coalescent processes which admit multiple mergers of ancestral lineages looking back in time. Among the genealogical properties we consider are the probability that the most recent common ancestor is shared between the complete sample and the subsample nested within the complete sample; we also compare the lengths of `internal' branches of nested genealogies between different coalescent processes. The results indicate how `informative' a subsample is about the properties of the larger complete sample, how much information is gained by increasing the sample size, and how the `informativeness' of the subsample varies between different coalescent processes.

Robustness of reliable change indices to variability in Parkinson's disease with mild cognitive impairment.

PubMed

Turner, T H; Renfroe, J B; Elm, J; Duppstadt-Delambo, A; Hinson, V K

2016-01-01

Ability to identify change is crucial for measuring response to interventions and tracking disease progression. Beyond psychometrics, investigations of Parkinson's disease with mild cognitive impairment (PD-MCI) must consider fluctuating medication, motor, and mental status. One solution is to employ 90% reliable change indices (RCIs) from test manuals to account for account measurement error and practice effects. The current study examined robustness of 90% RCIs for 19 commonly used executive function tests in 14 PD-MCI subjects assigned to the placebo arm of a 10-week randomized controlled trial of atomoxetine in PD-MCI. Using 90% RCIs, the typical participant showed spurious improvement on one measure, and spurious decline on another. Reliability estimates from healthy adults standardization samples and PD-MCI were similar. In contrast to healthy adult samples, practice effects were minimal in this PD-MCI group. Separate 90% RCIs based on the PD-MCI sample did not further reduce error rate. In the present study, application of 90% RCIs based on healthy adults in standardization samples effectively reduced misidentification of change in a sample of PD-MCI. Our findings support continued application of 90% RCIs when using executive function tests to assess change in neurological populations with fluctuating status.

Prevalence and Associated Factors of Depression in General Population of Korea: Results from the Korea National Health and Nutrition Examination Survey, 2014

PubMed Central

2017-01-01

Depressive disorder is a common mental illness and remains a major cause of morbidity worldwide. The present study, a cross-sectional, nationwide, population-based survey assessed the prevalence of depression in the general population of Korea through a random sampling of the non-institutionalized population for the Korea National Health and Nutrition Examination Survey (KNHANES) VI. The Patient Health Questionnaire (PHQ)-9 was first introduced into the KNHANES to detect depression. The point prevalence of depression (PHQ score of 10 or higher) was 6.7% (95% confidence interval [CI], 5.7–7.6) in 4,949 subjects. Based on the analysis using the diagnostic algorithm of the PHQ-9, the prevalence of major depressive disorder was 2.7% (95% CI, 2.2–3.3). Multiple logistic regression analysis, after adjusting the sociodemographic variables, also showed that the factors associated with depression were perceived stress and health status. This study reported for the first time that the point prevalence of depression screened using the PHQ-9 in this nationwide survey of the Korean population was similar to that of the western countries. As the KNHANES to detect depression is conducted biennially, further studies on the accumulated data are expected in the future. PMID:28960042

45 CFR 5b.11 - Exempt systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Surveys Conduct in Random Samples of the U.S. Population; (B) The Health Manpower Inventories and Surveys...) of the Act and the individual has been, as a result of the maintenance of the record, denied a right...

45 CFR 5b.11 - Exempt systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Surveys Conduct in Random Samples of the U.S. Population; (B) The Health Manpower Inventories and Surveys...) of the Act and the individual has been, as a result of the maintenance of the record, denied a right...

The densest terrestrial vertebrate

USGS Publications Warehouse

Rodda, G.H.; Perry, G.; Rondeau, R.J.; Lazell, J.

2001-01-01

An understanding of the abundance of organisms is central to understanding ecology, but many population density estimates are unrepresentative because they were obtained from study areas chosen for the high abundance of the target species. For example, from a pool of 1072 lizard density estimates that we compiled from the literature, we sampled 303 estimates and scored each for its assessment of the degree to which the study site was representative. Less than half (45%) indicated that the study area was chosen to be representative of the population or habitat. An additional 15% reported that individual plots or transects were chosen randomly, but this often indicated only that the sample points were located randomly within a study area chosen for its high abundance of the target species. The remainder of the studies either gave no information or specified that the study area was chosen because the focal species was locally abundant.

Network Structure and the Risk for HIV Transmission Among Rural Drug Users

PubMed Central

Young, A. M.; Jonas, A. B.; Mullins, U. L.; Halgin, D. S.

2012-01-01

Research suggests that structural properties of drug users’ social networks can have substantial effects on HIV risk. The purpose of this study was to investigate if the structural properties of Appalachian drug users’ risk networks could lend insight into the potential for HIV transmission in this population. Data from 503 drug users recruited through respondent-driven sampling were used to construct a sociometric risk network. Network ties represented relationships in which partners had engaged in unprotected sex and/or shared injection equipment. Compared to 1,000 randomly generated networks, the observed network was found to have a larger main component and exhibit more cohesiveness and centralization than would be expected at random. Thus, the risk network structure in this sample has many structural characteristics shown to be facilitative of HIV transmission. This underscores the importance of primary prevention in this population and prompts further investigation into the epidemiology of HIV in the region. PMID:23184464

A community-wide campaign to promote physical activity in middle-aged and elderly people: a cluster randomized controlled trial

PubMed Central

2013-01-01

Background We aimed to evaluate the effectiveness of a community-wide campaign (CWC) for promoting physical activity in middle-aged and elderly people. Methods A cluster randomized controlled trial (RCT) with a community as the unit of randomization was performed using a population-based random-sampled evaluation by self-administered questionnaires in the city of Unnan, Shimane Prefecture, Japan. The evaluation sample included 6000 residents aged 40 to 79 years. We randomly allocated nine communities to the intervention group and three to the control group. The intervention was a CWC from 2009 to 2010 to promote physical activity, and it comprised information, education, and support delivery. The primary outcome was a change in engaging in regular aerobic, flexibility, and/or muscle-strengthening activities evaluated at the individual level. Results In total, 4414 residents aged 40–79 years responded to a self-administered questionnaire (73.6% response rate). Awareness of the CWC was 79% in the intervention group. Awareness and knowledge were significantly different between the intervention and control groups, although there were no significant differences in belief and intention. The 1-year CWC did not significantly promote the recommended level of physical activity (adjusted odds ratio: 0.97; 95% confidence interval: 0.84–1.14). Conclusions This cluster RCT showed that the CWC did not promote physical activity in 1 year. Significant differences were observed in awareness and knowledge between intervention and control groups as short-term impacts of the campaign. Trial registration UMIN-CTR UMIN000002683 PMID:23570536

Effects of language of assessment on the measurement of acculturation: measurement equivalence and cultural frame switching.

PubMed

Schwartz, Seth J; Benet-Martínez, Verónica; Knight, George P; Unger, Jennifer B; Zamboanga, Byron L; Des Rosiers, Sabrina E; Stephens, Dionne P; Huang, Shi; Szapocznik, José

2014-03-01

The present study used a randomized design, with fully bilingual Hispanic participants from the Miami area, to investigate 2 sets of research questions. First, we sought to ascertain the extent to which measures of acculturation (Hispanic and U.S. practices, values, and identifications) satisfied criteria for linguistic measurement equivalence. Second, we sought to examine whether cultural frame switching would emerge--that is, whether latent acculturation mean scores for U.S. acculturation would be higher among participants randomized to complete measures in English and whether latent acculturation mean scores for Hispanic acculturation would be higher among participants randomized to complete measures in Spanish. A sample of 722 Hispanic students from a Hispanic-serving university participated in the study. Participants were first asked to complete translation tasks to verify that they were fully bilingual. Based on ratings from 2 independent coders, 574 participants (79.5% of the sample) qualified as fully bilingual and were randomized to complete the acculturation measures in either English or Spanish. Theoretically relevant criterion measures--self-esteem, depressive symptoms, and personal identity--were also administered in the randomized language. Measurement equivalence analyses indicated that all of the acculturation measures--Hispanic and U.S. practices, values, and identifications-met criteria for configural, weak/metric, strong/scalar, and convergent validity equivalence. These findings indicate that data generated using acculturation measures can, at least under some conditions, be combined or compared across languages of administration. Few latent mean differences emerged. These results are discussed in terms of the measurement of acculturation in linguistically diverse populations. 2014 APA

Effects of Language of Assessment on the Measurement of Acculturation: Measurement Equivalence and Cultural Frame Switching

PubMed Central

Schwartz, Seth J.; Benet-Martínez, Verónica; Knight, George P.; Unger, Jennifer B.; Zamboanga, Byron L.; Des Rosiers, Sabrina E.; Stephens, Dionne; Huang, Shi; Szapocznik, José

2014-01-01

The present study used a randomized design, with fully bilingual Hispanic participants from the Miami area, to investigate two sets of research questions. First, we sought to ascertain the extent to which measures of acculturation (heritage and U.S. practices, values, and identifications) satisfied criteria for linguistic measurement equivalence. Second, we sought to examine whether cultural frame switching would emerge – that is, whether latent acculturation mean scores for U.S. acculturation would be higher among participants randomized to complete measures in English, and whether latent acculturation mean scores for Hispanic acculturation would be higher among participants randomized to complete measures in Spanish. A sample of 722 Hispanic students from a Hispanic-serving university participated in the study. Participants were first asked to complete translation tasks to verify that they were fully bilingual. Based on ratings from two independent coders, 574 participants (79.5% of the sample) qualified as fully bilingual and were randomized to complete the acculturation measures in either English or Spanish. Theoretically relevant criterion measures – self-esteem, depressive symptoms, and personal identity – were also administered in the randomized language. Measurement equivalence analyses indicated that all of the acculturation measures – Hispanic and U.S. practices, values, and identifications – met criteria for configural, weak/metric, strong/scalar, and convergent validity equivalence. These findings indicate that data generated using acculturation measures can, at least under some conditions, be combined or compared across languages of administration. Few latent mean differences emerged. These results are discussed in terms of the measurement of acculturation in linguistically diverse populations. PMID:24188146

Web Intervention for Adolescents Affected by Disaster: Population-Based Randomized Controlled Trial

PubMed Central

Ruggiero, Kenneth J.; Price, Matthew; Adams, Zachary; Stauffacher, Kirstin; McCauley, Jenna; Danielson, Carla Kmett; Knapp, Rebecca; Hanson, Rochelle F.; Davidson, Tatiana M.; Amstadter, Ananda B.; Carpenter, Matthew J.; Saunders, Benjamin E.; Kilpatrick, Dean G.; Resnick, Heidi S.

2015-01-01

Objective To assess the efficacy of Bounce Back Now (BBN), a modular, web-based intervention for disaster-affected adolescents and their parents. Method A population-based randomized controlled trial used address-based sampling to enroll 2,000 adolescents and parents from communities affected by tornadoes in Joplin, MO, and Alabama. Data collection via baseline and follow-up semi-structured telephone interviews was completed between September 2011 and August 2013. All families were invited to access the BBN study web portal irrespective of mental health status at baseline. Families who accessed the web portal were assigned randomly to 3 groups: (1) BBN, which featured modules for adolescents and parents targeting adolescents’ mental health symptoms; (2) BBN plus additional modules targeting parents’ mental health symptoms; or (3) assessment only. The primary outcomes were adolescent symptoms of posttraumatic stress disorder (PTSD) and depression. Results Nearly 50% of families accessed the web portal. Intent-to-treat analyses revealed time × condition interactions for PTSD symptoms (B=−0.24, SE=0.08, p<.01) and depressive symptoms (B=−0.23, SE=0.09, p<.01). Post-hoc comparisons revealed fewer PTSD and depressive symptoms for adolescents in the experimental vs. control conditions at 12-month follow-up (PTSD: B=−0.36, SE=0.19, p=.06; depressive symptoms: B=−0.42, SE=0.19, p=0.03). A time × condition interaction also was found favoring the BBN vs. BBN + parent self-help condition for PTSD symptoms (B=0.30, SE=0.12, p=.02), but not depressive symptoms (B=0.12, SE=0.12, p=.33). Conclusion Results supported the feasibility and initial efficacy of BBN as a scalable disaster mental health intervention for adolescents. Technology-based solutions have tremendous potential value if found to reduce the mental health burden of disasters. PMID:26299292

Numeric score-based conditional and overall change-in-status indices for ordered categorical data.

PubMed

Lyles, Robert H; Kupper, Lawrence L; Barnhart, Huiman X; Martin, Sandra L

2015-11-30

Planned interventions and/or natural conditions often effect change on an ordinal categorical outcome (e.g., symptom severity). In such scenarios, it is sometimes desirable to assign a priori scores to observed changes in status, typically giving higher weight to changes of greater magnitude. We define change indices for such data based upon a multinomial model for each row of a c × c table, where the rows represent the baseline status categories. We distinguish an index designed to assess conditional changes within each baseline category from two others designed to capture overall change. One of these overall indices measures expected change across a target population. The other is scaled to capture the proportion of total possible change in the direction indicated by the data, so that it ranges from -1 (when all subjects finish in the least favorable category) to +1 (when all finish in the most favorable category). The conditional assessment of change can be informative regardless of how subjects are sampled into the baseline categories. In contrast, the overall indices become relevant when subjects are randomly sampled at baseline from the target population of interest, or when the investigator is able to make certain assumptions about the baseline status distribution in that population. We use a Dirichlet-multinomial model to obtain Bayesian credible intervals for the conditional change index that exhibit favorable small-sample frequentist properties. Simulation studies illustrate the methods, and we apply them to examples involving changes in ordinal responses for studies of sleep deprivation and activities of daily living. Copyright © 2015 John Wiley & Sons, Ltd.

A Population-Based Assessment of Heartburn in Urban Black Americans

PubMed Central

Friedenberg, Frank K.; Makipour, Kian; Palit, Amiya; Shah, Sweetang; Vanar, Vishwas; Richter, Joel E.

2013-01-01

Background Prevalence data for heartburn in the urban Black American community is lacking. In order to estimate prevalence for this community we analyzed data from an ongoing cohort study in progress at our hospital. Comprehensive interviews allowed for exploration of factors associated with heartburn. Methods Complex, stratified sampling design. Survey invitations are hand delivered to random blocks in a single zip code tabulation area. One member per eligible household is invited to complete a computer-based survey. Heartburn was defined as ≥ 3 days/week of symptoms as defined by the Montreal Definition and Classification of GERD. Scaling and weighting factors were utilized to estimate population-level prevalence. Multivariate logistic regression was used to identify independent predictor variables for heartburn. Results Enrolled 379 participants corresponding to a weighted sample size of 22,409 (20,888–23,930) citizens. Demographic characteristics of the sample closely matched those of the entire targeted population. Overall, the weighted prevalence of heartburn ≥ 3 times per week was 17.6% (16.4%–18.8%). Variables independently associated with heartburn were BMI, daily caloric and fat intake, diabetes mellitus (OR=2.95; 2.59–3.36), cigarette smoking, and alcohol consumption (OR=2.55; 2.25–2.89). Factors inversely associated included illicit drug use and increased physical activity. Waist: hip ratio showed no relationship. Conclusions The prevalence of heartburn ≥ 3 times per week is high in the Black American community. Adverse lifestyle behaviors showed particularly important associations. Our study needs to be replicated in other communities with similar demographics. PMID:23237330

The Effect of Teaching Model ‘Learning Cycles 5E’ toward Students’ Achievement in Learning Mathematic at X Years Class SMA Negeri 1 Banuhampu 2013/2014 Academic Year

NASA Astrophysics Data System (ADS)

Yeni, N.; Suryabayu, E. P.; Handayani, T.

2017-02-01

Based on the survey showed that mathematics teacher still dominated in teaching and learning process. The process of learning is centered on the teacher while the students only work based on instructions provided by the teacher without any creativity and activities that stimulate students to explore their potential. Realized the problem above the writer interested in finding the solution by applying teaching model ‘Learning Cycles 5E’. The purpose of his research is to know whether teaching model ‘Learning Cycles 5E’ is better than conventional teaching in teaching mathematic. The type of the research is quasi experiment by Randomized Control test Group Only Design. The population in this research were all X years class students. The sample is chosen randomly after doing normality, homogeneity test and average level of students’ achievement. As the sample of this research was X.7’s class as experiment class used teaching model learning cycles 5E and X.8’s class as control class used conventional teaching. The result showed us that the students achievement in the class that used teaching model ‘Learning Cycles 5E’ is better than the class which did not use the model.

Prevalence of modifiable cardiovascular risk factors among tea garden and general population in Dibrugarh, Assam, India.

PubMed

Mahanta, Tulika G; Joshi, Rajnish; Mahanta, Bhupendra N; Xavier, Denis

2013-09-01

Risk factors for cardiovascular disease (CVD) are multifactorial. Previous research has reported a high prevalence of CVD risk factors in tea-garden workers. This study was conducted to assess prevalence and level of modifiable cardiovascular risk factors among tea-garden and general population in Dibrugarh, Assam. A community-based cross-sectional study using the World Health Organization's (WHO) Stepwise methodology was conducted in Dibrugarh District of Assam. A multistep random sampling was done to include adults aged 35 years and above, with an intended equal sampling from tea-garden and general population. INTERHEART modifiable non-laboratory based risk score was estimated. Salt consumption was estimated using questionnaire-based methods in both subgroups. A total of 2826 individuals participated in the study (1231 [43.6%] tea-garden workers; 1595 [56.4%] general population). Tobacco consumption was higher in tea-garden workers as compared with general population (85.2% vs. 41.7% (p < 0.0001). Mean daily per-capita salt consumption was also significantly higher among tea-garden workers (29.60 vs. 22.89 g, p = 0.0001). Overall prevalence of hypertension was similar (44.4% vs. 45.2%), but among those who had hypertension, prevalence of undiagnosed hypertension was higher in tea-garden workers (82.8% vs. 74.4%, p < 0.0001). Tea-garden workers had lower BMI, were more physically active, and had a lower prevalence of diabetes mellitus and metabolic syndrome. Their INTERHEART modifiable risk score was also lower (1.44 [2.5] vs. 1.79 [2.8], p = 0.001). High prevalence of modifiable risk factors like tobacco consumption, high salt intake and high prevalence of hypertension indicates the need for early implementation of preventive actions in this population. Copyright © 2013 Ministry of Health, Saudi Arabia. Published by Elsevier Ltd. All rights reserved.

The prevalence of crash risk factors in a population-based study of motorcycle riders.

PubMed

de Rome, Liz; Fitzharris, Michael; Baldock, Matthew; Fernandes, Ralston; Ma, Alice; Brown, Julie

2016-09-01

Motorcyclists represent an increasing proportion of road traffic casualties but, while factors associated with crashes are readily identifiable, little is known about the prevalence of those risk factors in the motorcycling population. A stratified random-sampling frame was used to survey the population of registered motorcycles owners in New South Wales (NSW) when they attended motor registry offices. The postal codes in the State database of registered motorcycle were used to stratify the population into quartiles based on socioeconomic characteristics and to determine sample weights. Participants (n=506) represented 47% of eligible riders approached. On average participants were aged 43, rode 7h/week and had 17 years of riding experience. Estimates based on multiple ownership rates suggest motorcycle registration numbers exceed the active riding population by approximately 15%. Less than half rode under 101km/week, 25% rode over 300km/week and just 42% rode every day. More rode frequently for leisure (70%) than for commuting (53%) and over half rarely rode in dark (52%) or wet (67%) conditions. Most wore protective clothing - helmets (100%), jackets (82%), pants (56%), boots (57%) and gloves (73%). Those with traffic infringements (32%) were mostly for driving (25%), not riding (10%) offences. In the past year, 13% had one or more motorcycle crashes including minor spills and 76% one or more near-crash experiences. The youngest riders (15-19) reported the highest rates of exposure in kilometres, hours, frequency of riding and commuting. They also reported lower crash involvement (3%) but more near-crashes (80%). This study provides an account of the prevalence of key risk factors across age groups in a population of active motorcycle riders in NSW. Novice riders were represented in all age groups although most novices were under 40 years. These data can be used to guide the development of targeted countermeasures aimed at improving motorcycling safety for riders of different age groups. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Prevalence and risk factors for functional bowel disorders in South China: a population based study using the Rome III criteria.

PubMed

Long, Y; Huang, Z; Deng, Y; Chu, H; Zheng, X; Yang, J; Zhu, Y; Fried, M; Fox, M; Dai, N

2017-01-01

Functional bowel disorders (FBDs) such as irritable bowel syndrome (IBS) impact on quality of life and health care resources. It is uncertain whether patients with functional digestive symptoms have similar characteristics in different populations. This population-based study assessed the prevalence and identified risk factors for these disorders in South-East China. Five communities were selected at random and invitations distributed to a representative sample (block randomization). Questionnaires were completely supervised by investigators. Demographic and medical data with FBD symptoms (Rome III criteria), psychological condition, life event stress, and quality of life were collected. Functional bowel disorder prevalence was 41.6% in 1999/2115 (94.5%) completed questionnaires: 9.9% functional constipation (FC), 6.8% bloating (FB), 6.5% diarrhea (FD), 5.9% IBS (IBS-D 47.1%, IBS-M 23.9%, IBS-C 12.8%, IBS-U 16.2%), and 12.6% unspecified. Similar numbers of men and women had FBDs or IBS (overall; 51.3% male vs 48.7% female, P=.796); however, there was female predominance in FC (62.1%, P<.001) and FB (58.5%, P=.038). FBDs were associated with greater anxiety, depression, life event stress, and a lower quality of life compared with those without symptoms (all, P<.0001). Logistic regression identified medical co-morbidity, anxiety/depression, and life event stress as independent risk factors for these disorders. Functional bowel disorders are as common in South China as in western populations. A similar number of men and women report FBDs and IBS. Only FC and FB are more prevalent in females. Independent risk factors associated with FBDs included physical and psychosocial stressors. © 2016 John Wiley & Sons Ltd.

Deciphering the Routes of invasion of Drosophila suzukii by Means of ABC Random Forest.

PubMed

Fraimout, Antoine; Debat, Vincent; Fellous, Simon; Hufbauer, Ruth A; Foucaud, Julien; Pudlo, Pierre; Marin, Jean-Michel; Price, Donald K; Cattel, Julien; Chen, Xiao; Deprá, Marindia; François Duyck, Pierre; Guedot, Christelle; Kenis, Marc; Kimura, Masahito T; Loeb, Gregory; Loiseau, Anne; Martinez-Sañudo, Isabel; Pascual, Marta; Polihronakis Richmond, Maxi; Shearer, Peter; Singh, Nadia; Tamura, Koichiro; Xuéreb, Anne; Zhang, Jinping; Estoup, Arnaud

2017-04-01

Deciphering invasion routes from molecular data is crucial to understanding biological invasions, including identifying bottlenecks in population size and admixture among distinct populations. Here, we unravel the invasion routes of the invasive pest Drosophila suzukii using a multi-locus microsatellite dataset (25 loci on 23 worldwide sampling locations). To do this, we use approximate Bayesian computation (ABC), which has improved the reconstruction of invasion routes, but can be computationally expensive. We use our study to illustrate the use of a new, more efficient, ABC method, ABC random forest (ABC-RF) and compare it to a standard ABC method (ABC-LDA). We find that Japan emerges as the most probable source of the earliest recorded invasion into Hawaii. Southeast China and Hawaii together are the most probable sources of populations in western North America, which then in turn served as sources for those in eastern North America. European populations are genetically more homogeneous than North American populations, and their most probable source is northeast China, with evidence of limited gene flow from the eastern US as well. All introduced populations passed through bottlenecks, and analyses reveal five distinct admixture events. These findings can inform hypotheses concerning how this species evolved between different and independent source and invasive populations. Methodological comparisons indicate that ABC-RF and ABC-LDA show concordant results if ABC-LDA is based on a large number of simulated datasets but that ABC-RF out-performs ABC-LDA when using a comparable and more manageable number of simulated datasets, especially when analyzing complex introduction scenarios. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Forecasting the brittle failure of heterogeneous, porous geomaterials

NASA Astrophysics Data System (ADS)

Vasseur, Jérémie; Wadsworth, Fabian; Heap, Michael; Main, Ian; Lavallée, Yan; Dingwell, Donald

2017-04-01

Heterogeneity develops in magmas during ascent and is dominated by the development of crystal and importantly, bubble populations or pore-network clusters which grow, interact, localize, coalesce, outgas and resorb. Pore-scale heterogeneity is also ubiquitous in sedimentary basin fill during diagenesis. As a first step, we construct numerical simulations in 3D in which randomly generated heterogeneous and polydisperse spheres are placed in volumes and which are permitted to overlap with one another, designed to represent the random growth and interaction of bubbles in a liquid volume. We use these simulated geometries to show that statistical predictions of the inter-bubble lengthscales and evolving bubble surface area or cluster densities can be made based on fundamental percolation theory. As a second step, we take a range of well constrained random heterogeneous rock samples including sandstones, andesites, synthetic partially sintered glass bead samples, and intact glass samples and subject them to a variety of stress loading conditions at a range of temperatures until failure. We record in real time the evolution of the number of acoustic events that precede failure and show that in all scenarios, the acoustic event rate accelerates toward failure, consistent with previous findings. Applying tools designed to forecast the failure time based on these precursory signals, we constrain the absolute error on the forecast time. We find that for all sample types, the error associated with an accurate forecast of failure scales non-linearly with the lengthscale between the pore clusters in the material. Moreover, using a simple micromechanical model for the deformation of porous elastic bodies, we show that the ratio between the equilibrium sub-critical crack length emanating from the pore clusters relative to the inter-pore lengthscale, provides a scaling for the error on forecast accuracy. Thus for the first time we provide a potential quantitative correction for forecasting the failure of porous brittle solids that build the Earth's crust.

Altered self-perception in adult survivors treated for a CNS tumor in childhood or adolescence: population-based outcomes compared with the general population

PubMed Central

Hörnquist, Lina; Rickardsson, Jenny; Lannering, Birgitta; Gustafsson, Göran; Boman, Krister K.

2015-01-01

Background Survivors of pediatric CNS tumors are at risk for persistent tumor/treatment-related morbidity, physical disability and social consequences that may alter self-perception, vital for self-identity, mental health and quality of survival. We studied the long-term impact of childhood CNS tumors and their treatment on the self-perception of adult survivors and compared outcomes with those of the general population. Methods The cohort included 697 Swedish survivors diagnosed with a primary CNS tumor during 1982–2001. Comparison data were randomly collected from a stratified general population sample. Survivors and general population individuals were compared as regards self-perception in 5 domains: body image, sports/physical activities, peers, work, and family, and with a global self-esteem index. Within the survivor group, determinants of impact on self-perception were identified. Results The final analyzed sample included 528 survivors, 75.8% of the entire national cohort. The control sample consisted of 995, 41% of 2500 addressed. Survivors had significantly poorer self-perception outcomes in domains of peers, work, body image, and sports/physical activities, and in the global self-perception measure, compared with those of the general population (all P < .001). Within the survivor group, female gender and persistent visible physical sequelae predicted poorer outcomes in several of the studied domains. Tumor type and a history of cranial radiation therapy were associated with outcomes. Conclusion An altered self-perception is a potential late effect in adult survivors of pediatric CNS tumors. Self-perception and self-esteem are significant elements of identity, mental health and quality of survival. Therefore, care and psychosocial follow-up of survivors should include measures for identifying disturbances and for assessing the need for psychosocial intervention. PMID:25332406

Mean population salt intake estimated from 24-h urine samples and spot urine samples: a systematic review and meta-analysis.

PubMed

Huang, Liping; Crino, Michelle; Wu, Jason H Y; Woodward, Mark; Barzi, Federica; Land, Mary-Anne; McLean, Rachael; Webster, Jacqui; Enkhtungalag, Batsaikhan; Neal, Bruce

2016-02-01

Estimating equations based on spot urine samples have been identified as a possible alternative approach to 24-h urine collections for determining mean population salt intake. This review compares estimates of mean population salt intake based upon spot and 24-h urine samples. We systematically searched for all studies that reported estimates of daily salt intake based upon both spot and 24-h urine samples for the same population. The associations between the two were quantified and compared overall and in subsets of studies. A total of 538 records were identified, 108 were assessed as full text and 29 were included. The included studies involved 10,414 participants from 34 countries and made 71 comparisons available for the primary analysis. Overall average population salt intake estimated from 24-h urine samples was 9.3 g/day compared with 9.0 g/day estimated from the spot urine samples. Estimates based upon spot urine samples had excellent sensitivity (97%) and specificity (100%) at classifying mean population salt intake as above or below the World Health Organization maximum target of 5 g/day. Compared with the 24-h samples, estimates based upon spot urine overestimated intake at lower levels of consumption and underestimated intake at higher levels of consumption. Estimates of mean population salt intake based upon spot urine samples can provide countries with a good indication of mean population salt intake and whether action on salt consumption is required. Published by Oxford University Press on behalf of the International Epidemiological Association 2015. This work is written by US Government employees and is in the public domain in the US.

Comparing decision making between cancer patients and the general population: thoughts, emotions, or social influence?

PubMed

Yang, Z Janet; McComas, Katherine A; Gay, Geri K; Leonard, John P; Dannenberg, Andrew J; Dillon, Hildy

2012-01-01

This study extends a risk information seeking and processing model to explore the relative effect of cognitive processing strategies, positive and negative emotions, and normative beliefs on individuals' decision making about potential health risks. Most previous research based on this theoretical framework has examined environmental risks. Applying this risk communication model to study health decision making presents an opportunity to explore theoretical boundaries of the model, while also bringing this research to bear on a pressing medical issue: low enrollment in clinical trials. Comparative analysis of data gathered from 2 telephone surveys of a representative national sample (n = 500) and a random sample of cancer patients (n = 411) indicated that emotions played a more substantive role in cancer patients' decisions to enroll in a potential trial, whereas cognitive processing strategies and normative beliefs had greater influences on the decisions of respondents from the national sample.

Is a 'convenience' sample useful for estimating immunization coverage in a small population?

PubMed

Weir, Jean E; Jones, Carrie

2008-01-01

Rapid survey methodologies are widely used for assessing immunization coverage in developing countries, approximating true stratified random sampling. Non-random ('convenience') sampling is not considered appropriate for estimating immunization coverage rates but has the advantages of low cost and expediency. We assessed the validity of a convenience sample of children presenting to a travelling clinic by comparing the coverage rate in the convenience sample to the true coverage established by surveying each child in three villages in rural Papua New Guinea. The rate of DTF immunization coverage as estimated by the convenience sample was within 10% of the true coverage when the proportion of children in the sample was two-thirds or when only children over the age of one year were counted, but differed by 11% when the sample included only 53% of the children and when all eligible children were included. The convenience sample may be sufficiently accurate for reporting purposes and is useful for identifying areas of low coverage.

Consequences of harvesting for genetic diversity in American ginseng (Panax quinquefolius L.): A simulation study

USGS Publications Warehouse

Cruse-Sanders, J. M.; Hamrick, J.L.; Ahumada, J.A.

2005-01-01

American ginseng, Panax quinquefolius L., is one of the most heavily traded medicinal plants in North America. The effect of harvest on genetic diversity in ginseng was measured with a single generation culling simulation program. Culling scenarios included random harvest at varying levels, legal limit random harvest and legal limit mature plant harvest. The legal limit was determined by the proportion of legally harvestable plants per population (% mature plants per population). Random harvest at varying levels resulted in significant loss of genetic diversity, especially allelic richness. Relative to initial levels, average within-population genetic diversity (H e) was significantly lower when plants were culled randomly at the legal limit (Mann-Whitney U = 430, p < 0.001) or when only mature plants were culled (Mann-Whitney U = 394, p < 0.01). Within-population genetic diversity was significantly higher with legal limit mature plant harvest (H e = 0.068) than when plants were culled randomly at the legal limit (H e = 0.064; U = 202, p < 0.01). Based on these simulations of harvest over one generation, we recommend that harvesting fewer than the proportion of mature plants could reduce the negative genetic effects of harvest on ginseng populations. ?? Springer 2005.

Comparing population size estimators for plethodontid salamanders

USGS Publications Warehouse

Bailey, L.L.; Simons, T.R.; Pollock, K.H.

2004-01-01

Despite concern over amphibian declines, few studies estimate absolute abundances because of logistic and economic constraints and previously poor estimator performance. Two estimation approaches recommended for amphibian studies are mark-recapture and depletion (or removal) sampling. We compared abundance estimation via various mark-recapture and depletion methods, using data from a three-year study of terrestrial salamanders in Great Smoky Mountains National Park. Our results indicate that short-term closed-population, robust design, and depletion methods estimate surface population of salamanders (i.e., those near the surface and available for capture during a given sampling occasion). In longer duration studies, temporary emigration violates assumptions of both open- and closed-population mark-recapture estimation models. However, if the temporary emigration is completely random, these models should yield unbiased estimates of the total population (superpopulation) of salamanders in the sampled area. We recommend using Pollock's robust design in mark-recapture studies because of its flexibility to incorporate variation in capture probabilities and to estimate temporary emigration probabilities.

Old worries and new anxieties: behavioral symptoms and mild cognitive impairment in a population study.

PubMed

Andreescu, Carmen; Teverovsky, Esther; Fu, Bo; Hughes, Tiffany F; Chang, Chung-Chou H; Ganguli, Mary

2014-03-01

To disentangle the complex associations of depression and anxiety with mild cognitive impairment (MCI) at the population level. We examined subgroups of anxiety symptoms and depression symptom profiles in relation to MCI, which we defined using both cognitive and functional approaches. We used an epidemiologic, cross-sectional study with an age-stratified, random, population-based sample of 1,982 individuals aged 65 years and over. Three definitions of MCI were used: 1) a purely cognitive classification into amnestic and nonamnestic MCI, 2) a combined cognitive-functional definition by International Working Group (IWG) criteria, and 3) a purely functional definition by the Clinical Dementia Rating (CDR) of 0.5. Three depression profiles were identified by factor analysis of the modified Center for Epidemiological Studies-Depression Scale: core mood, self-esteem/interpersonal, and apathy/neurovegetative profiles. Three anxiety groups, chronic mild worry, chronic severe anxiety, and recent-onset anxiety, were based on screening questions. Recent-onset anxiety was associated with MCI by nonamnestic and IWG criteria, chronic severe anxiety was associated with MCI by all definitions, and chronic mild worry was associated with none. Of the depression profiles, the core mood profile was associated with CDR-defined MCI, the apathy/neurovegetative profile was associated with MCI by amnestic, IWG, and CDR definitions, and the self-esteem/interpersonal profile was associated with none. In this population-based sample, subgroups with different anxiety and depression profiles had different relationships with cognitive and functional definitions of MCI. Anxiety, depression, and MCI are all multidimensional entities, interacting in complex ways that may shed light on underlying neural mechanisms. Copyright © 2014 American Association for Geriatric Psychiatry. Published by Elsevier Inc. All rights reserved.

The population-based Barcelona-Asymptomatic Intracranial Atherosclerosis Study (ASIA): rationale and design.

PubMed

López-Cancio, Elena; Dorado, Laura; Millán, Mónica; Reverté, Silvia; Suñol, Anna; Massuet, Anna; Mataró, María; Galán, Amparo; Alzamora, Maite; Pera, Guillem; Torán, Pere; Dávalos, Antoni; Arenillas, Juan F

2011-02-17

Large-artery intracranial atherosclerosis may be the most frequent cause of ischemic stroke worldwide. Traditional approaches have attempted to target the disease when it is already symptomatic. However, early detection of intracranial atherosclerosis may allow therapeutic intervention while the disease is still asymptomatic. The prevalence and natural history of asymptomatic intracranial atherosclerosis in Caucasians remain unclear. The aims of the Barcelona-ASymptomatic Intracranial Atherosclerosis (ASIA) study are (1) to determine the prevalence of ASIA in a moderate-high vascular risk population, (2) to study its prognostic impact on the risk of suffering future major ischemic events, and (3) to identify predictors of the development, progression and clinical expression of this condition. Cross-over and cohort, population-based study. A randomly selected representative sample of 1,503 subjects with a mild-moderate-high vascular risk (as defined by a REGICOR score ≥ 5%) and with neither a history of cerebrovascular nor ischemic heart disease will be studied. At baseline, all individuals will undergo extracranial and transcranial Color-Coded Duplex (TCCD) ultrasound examinations to detect presence and severity of extra and intracranial atherosclerosis. Intracranial stenoses will be assessed by magnetic resonance angiography (MRA). Clinical and demographic variables will be recorded and blood samples will be drawn to investigate clinical, biological and genetic factors associated with the presence of ASIA. A long-term clinical and sonographic follow-up will be conducted thereafter to identify predictors of disease progression and of incident vascular events. The Barcelona-ASIA is a population-based study aiming to evaluate the prevalence and clinical importance of asymptomatic intracranial large-artery atherosclerosis in Caucasians. The ASIA project may provide a unique scientific resource to better understand the dynamics of intracranial atherosclerosis from its early stages and to identify new potential therapeutic targets for this condition.

Trends in obesity and diabetes prevalence in a Chilean urban population: 1993-2001.

PubMed

Cuevas, Ada; Molina, Alfredo; Rigotti, Attilio; Miquel, Juan Francisco; Marshall, Guillermo; Reyes, Soledad; Nervi, Flavio

2008-09-01

In recent years, the Chilean population has suffered significant lifestyle changes associated with the rapid socioeconomic development of the country. These changes can induce a significant increase in the prevalence of some chronic diseases, such as obesity, dyslipidemia, and diabetes mellitus. We aimed to assess diabetes mellitus, obesity, and hypercholesterolemia trends in a Chilean urban population followed between 1993 and 2001. A total of 1584 adults, living in Santiago, the capital of Chile, were randomly enrolled in a cross-sectional epidemiologic study in 1993. The same population was re-evaluated in 2001, recruiting 964 individuals from the original sample. Prevalences of diabetes mellitus, obesity, and hypercholesterolemia were determined according to standard criteria. We tested the significance of the differences between the observed prevalence of diabetes mellitus, obesity, and hypercholesterolemia in the 964 subjects evaluated in 2001 compared with the expected prevalence according to population aging based in data from 1993. In 1993, 3.8% of the sample population had diabetes mellitus, 21.8% had obesity, and 37.3 % exhibited hypercholesterolemia. In 2001, the observed prevalence of diabetes mellitus, obesity, and hypercholesterolemia was 10.1%, 32%, and 58%, respectively. The latter percentages were significantly higher than the expected prevalence according to the aging of the population (6.5% for diabetes mellitus, 27.7% for obesity, and 47.7 for hypercholesteromia). Our findings indicate that Chilean population has suffered an accelerated increase in the prevalence of diabetes mellitus, obesity, and hypercholesterolemia, due to the ongoing epidemiological transition that will lead to an enormous public health burden in the near future.

Culturally appropriate methodology in obtaining a representative sample of South Australian Aboriginal adults for a cross-sectional population health study: challenges and resolutions.

PubMed

Marin, Tania; Taylor, Anne Winifred; Grande, Eleonora Dal; Avery, Jodie; Tucker, Graeme; Morey, Kim

2015-05-19

The considerably lower average life expectancy of Aboriginal and Torres Strait Islander Australians, compared with non-Aboriginal and non-Torres Strait Islander Australians, has been widely reported. Prevalence data for chronic disease and health risk factors are needed to provide evidence based estimates for Australian Aboriginal and Torres Strait Islanders population health planning. Representative surveys for these populations are difficult due to complex methodology. The focus of this paper is to describe in detail the methodological challenges and resolutions of a representative South Australian Aboriginal population-based health survey. Using a stratified multi-stage sampling methodology based on the Australian Bureau of Statistics 2006 Census with culturally appropriate and epidemiological rigorous methods, 11,428 randomly selected dwellings were approached from a total of 209 census collection districts. All persons eligible for the survey identified as Aboriginal and/or Torres Strait Islander and were selected from dwellings identified as having one or more Aboriginal person(s) living there at the time of the survey. Overall, the 399 interviews from an eligible sample of 691 SA Aboriginal adults yielded a response rate of 57.7%. These face-to-face interviews were conducted by ten interviewers retained from a total of 27 trained Aboriginal interviewers. Challenges were found in three main areas: identification and recruitment of participants; interviewer recruitment and retainment; and using appropriate engagement with communities. These challenges were resolved, or at least mainly overcome, by following local protocols with communities and their representatives, and reaching agreement on the process of research for Aboriginal people. Obtaining a representative sample of Aboriginal participants in a culturally appropriate way was methodologically challenging and required high levels of commitment and resources. Adhering to these principles has resulted in a rich and unique data set that provides an overview of the self-reported health status for Aboriginal people living in South Australia. This process provides some important principles to be followed when engaging with Aboriginal people and their communities for the purpose of health research.

Attitudes toward Web-based distance learning among public health nurses in Taiwan: a questionnaire survey.

PubMed

Yu, Shu; Yang, Kuei-Feng

2006-08-01

Public health nurses (PHNs) often cannot receive in-service education due to limitations of time and space. Learning through the Internet has been a widely used technique in many professional and clinical nursing fields. The learner's attitude is the most important indicator that promotes learning. The purpose of this study was to investigate PHNs' attitude toward web-based learning and its determinants. This study conducted a cross-sectional research design. 369 health centers in Taiwan. The population involved this study was 2398 PHNs, and we used random sampling from this population. Finally, 329 PHNs completed the questionnaire, with a response rate of 84.0%. Data were collected by mailing the questionnaire. Most PHNs revealed a positive attitude toward web-based learning (mean+/-SD=55.02+/-6.39). PHNs who worked at village health centers, a service population less than 10,000, PHNs who had access to computer facility and on-line hardware in health centers and with better computer competence revealed more positive attitudes (p<0.01). Web-based learning is an important new way of in-service education; however, its success and hindering factors require further investigation. Individual computer competence is the main target for improvement, and educators should also consider how to establish a user-friendly learning environment on the Internet.

Use of antimicrobial drugs in general hospitals. I. Description of population and definition of methods.

PubMed

Townsend, T R; Shapiro, M; Rosner, B; Kass, E H

1979-06-01

The patterns of use of antimicrobial drugs in a random sample of general hosptials in Pennsylvania were studied. The sample was tested for validity, and all deaths and discharges were analyzed for 10 random days drawn across the year spanning July 1973 to June 1974. Methods were developed for abstracting the hospital records and for determining the reproducibility of the findings of the physician and nonphysician chart reviewers. More than 99% of the requested charts were available. In the 5,288 charts reviewed, most of the required data were readily available. The study population was 84% white and 58% female; most patients were in hospitals that had more than 300 beds and that were located in towns with populations of greater than 10,000. In 41% of the 2,070 antimicrobial courses administered to almost 30% of the patients, an explicit clinical statement of why the drug was being given could be found in the chart. The information for review was found in clinical charts, but in half of the charts, the information required was not on face sheets and discharge summaries.

Neutral theory, microbial practice: challenges in bacterial population genetics.

PubMed

Rocha, Eduardo P C

2018-04-19

Kimura's outstanding contributions to population genetics included many elegant theoretical results on the vagaries of alleles in populations. Once polymorphism data showed extensive variation in natural populations, these results led naturally to the Neutral Theory. In this article, I'll depart from some of these results to focus on four major open problems in microbial population genetics with direct implications to the study of molecular evolution: the lack of neutral polymorphism, the modeling of genetic exchanges, the population genetics of ill-defined populations, and the difficulty of untangling selection and demography in the light of the previous issues. Whilst studies in population genetics usually focus on single nucleotide polymorphism and allelic recombination, ignoring even small indels, a large fraction of genetic diversification in Bacteria results from horizontal gene transfer. Ignoring this fact defeats the purpose of population genetics: to characterize the genetic variation in populations and their adaptive effects. I'll argue that, following on Kimura's life work, one may need to develop new approaches to study microbes that reproduce asexually but are able to engage in gene exchanges with very distantly related organisms in a context where random sampling is often unachievable, populations are ill-defined, genetic linkage is strong, and random drift is rare.

Exploring cardiovascular health: the Healthy Life in Suriname (HELISUR) study. A protocol of a cross-sectional study

PubMed Central

Diemer, Frederieke S; Aartman, Jet Q; Karamat, Fares A; Baldew, Sergio M; Jarbandhan, Ameerani V; van Montfrans, Gert A; Oehlers, Glenn P; Brewster, Lizzy M

2014-01-01

Introduction Obesity, hypertension and diabetes are on a dramatic rise in low-income and middle-income countries, and this foretells an overwhelming increase in chronic disease burden from cardiovascular disease. Therefore, rapid action should be taken through preventive population-based programmes. However, in these regions, data on the population distribution of cardiovascular risk factors, and of intermediate and final end points for cardiovascular disease are scarce. The Healthy Life in Suriname (HELISUR) study is a cardiovascular population study in Suriname, which is part of the Caribbean Community. The HELISUR study is dedicated to provide data on risk factors and prevalent cardiovascular disease in the multiethnic population, which is mainly of African and Asian descent. Methods and analysis In a cross-sectional, observational population-based setting, a random representative sample of 1800 citizens aged between 18 and 70 years will be selected using a cluster household sampling method. Self-reported demographic, socioeconomic and (cardiovascular) health-related data will be collected. Physical examination will include the assessment of cardiovascular risk factors and prevalent cardiovascular disease. In addition, we will study cardiovascular haemodynamics non-invasively, as a novel intermediate outcome. Finally, fasting blood and overnight urine samples will be collected to monitor cardiometabolic risk factors. The main outcome will be descriptive in reporting the prevalence of risk factors and measures of (sub) clinical end organ damage, stratified for ethnicity and sex-age groups. Ethics and dissemination Ethical approval has been obtained from the State Secretary of Health. Data analysis and manuscript submission are scheduled for 2016. Findings will be disseminated in peer-reviewed journals, and at national, regional and international scientific meetings. Importantly, data will be presented to Surinamese policymakers and healthcare workers, to develop preventive strategies to combat the rapid rise of cardiovascular disease. PMID:25537786

Exploring cardiovascular health: the Healthy Life in Suriname (HELISUR) study. A protocol of a cross-sectional study.

PubMed

Diemer, Frederieke S; Aartman, Jet Q; Karamat, Fares A; Baldew, Sergio M; Jarbandhan, Ameerani V; van Montfrans, Gert A; Oehlers, Glenn P; Brewster, Lizzy M

2014-12-23

Obesity, hypertension and diabetes are on a dramatic rise in low-income and middle-income countries, and this foretells an overwhelming increase in chronic disease burden from cardiovascular disease. Therefore, rapid action should be taken through preventive population-based programmes. However, in these regions, data on the population distribution of cardiovascular risk factors, and of intermediate and final end points for cardiovascular disease are scarce. The Healthy Life in Suriname (HELISUR) study is a cardiovascular population study in Suriname, which is part of the Caribbean Community. The HELISUR study is dedicated to provide data on risk factors and prevalent cardiovascular disease in the multiethnic population, which is mainly of African and Asian descent. In a cross-sectional, observational population-based setting, a random representative sample of 1800 citizens aged between 18 and 70 years will be selected using a cluster household sampling method. Self-reported demographic, socioeconomic and (cardiovascular) health-related data will be collected. Physical examination will include the assessment of cardiovascular risk factors and prevalent cardiovascular disease. In addition, we will study cardiovascular haemodynamics non-invasively, as a novel intermediate outcome. Finally, fasting blood and overnight urine samples will be collected to monitor cardiometabolic risk factors. The main outcome will be descriptive in reporting the prevalence of risk factors and measures of (sub) clinical end organ damage, stratified for ethnicity and sex-age groups. Ethical approval has been obtained from the State Secretary of Health. Data analysis and manuscript submission are scheduled for 2016. Findings will be disseminated in peer-reviewed journals, and at national, regional and international scientific meetings. Importantly, data will be presented to Surinamese policymakers and healthcare workers, to develop preventive strategies to combat the rapid rise of cardiovascular disease. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

A Multilevel, Hierarchical Sampling Technique for Spatially Correlated Random Fields

DOE PAGES

Osborn, Sarah; Vassilevski, Panayot S.; Villa, Umberto

2017-10-26

In this paper, we propose an alternative method to generate samples of a spatially correlated random field with applications to large-scale problems for forward propagation of uncertainty. A classical approach for generating these samples is the Karhunen--Loève (KL) decomposition. However, the KL expansion requires solving a dense eigenvalue problem and is therefore computationally infeasible for large-scale problems. Sampling methods based on stochastic partial differential equations provide a highly scalable way to sample Gaussian fields, but the resulting parametrization is mesh dependent. We propose a multilevel decomposition of the stochastic field to allow for scalable, hierarchical sampling based on solving amore » mixed finite element formulation of a stochastic reaction-diffusion equation with a random, white noise source function. Lastly, numerical experiments are presented to demonstrate the scalability of the sampling method as well as numerical results of multilevel Monte Carlo simulations for a subsurface porous media flow application using the proposed sampling method.« less

A Multilevel, Hierarchical Sampling Technique for Spatially Correlated Random Fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osborn, Sarah; Vassilevski, Panayot S.; Villa, Umberto

In this paper, we propose an alternative method to generate samples of a spatially correlated random field with applications to large-scale problems for forward propagation of uncertainty. A classical approach for generating these samples is the Karhunen--Loève (KL) decomposition. However, the KL expansion requires solving a dense eigenvalue problem and is therefore computationally infeasible for large-scale problems. Sampling methods based on stochastic partial differential equations provide a highly scalable way to sample Gaussian fields, but the resulting parametrization is mesh dependent. We propose a multilevel decomposition of the stochastic field to allow for scalable, hierarchical sampling based on solving amore » mixed finite element formulation of a stochastic reaction-diffusion equation with a random, white noise source function. Lastly, numerical experiments are presented to demonstrate the scalability of the sampling method as well as numerical results of multilevel Monte Carlo simulations for a subsurface porous media flow application using the proposed sampling method.« less

The effect of team accelerated instruction on students’ mathematics achievement and learning motivation

NASA Astrophysics Data System (ADS)

Sri Purnami, Agustina; Adi Widodo, Sri; Charitas Indra Prahmana, Rully

2018-01-01

This study aimed to know the improvement of achievement and motivation of learning mathematics by using Team Accelerated Instruction. The research method used was the experiment with descriptive pre-test post-test experiment. The population in this study was all students of class VIII junior high school in Jogjakarta. The sample was taken using cluster random sampling technique. The instrument used in this research was questionnaire and test. Data analysis technique used was Wilcoxon test. It concluded that there was an increase in motivation and student achievement of class VII on linear equation system material by using the learning model of Team Accelerated Instruction. Based on the results of the learning model Team Accelerated Instruction can be used as a variation model in learning mathematics.

Handling nonresponse in surveys: analytic corrections compared with converting nonresponders.

PubMed

Jenkins, Paul; Earle-Richardson, Giulia; Burdick, Patrick; May, John

2008-02-01

A large health survey was combined with a simulation study to contrast the reduction in bias achieved by double sampling versus two weighting methods based on propensity scores. The survey used a census of one New York county and double sampling in six others. Propensity scores were modeled as a logistic function of demographic variables and were used in conjunction with a random uniform variate to simulate response in the census. These data were used to estimate the prevalence of chronic disease in a population whose parameters were defined as values from the census. Significant (p < 0.0001) predictors in the logistic function included multiple (vs. single) occupancy (odds ratio (OR) = 1.3), bank card ownership (OR = 2.1), gender (OR = 1.5), home ownership (OR = 1.3), head of household's age (OR = 1.4), and income >$18,000 (OR = 0.8). The model likelihood ratio chi-square was significant (p < 0.0001), with the area under the receiver operating characteristic curve = 0.59. Double-sampling estimates were marginally closer to population values than those from either weighting method. However, the variance was also greater (p < 0.01). The reduction in bias for point estimation from double sampling may be more than offset by the increased variance associated with this method.

Improving the evidence base in palliative care to inform practice and policy: thinking outside the box.

PubMed

Aoun, Samar M; Nekolaichuk, Cheryl

2014-12-01

The adoption of evidence-based hierarchies and research methods from other disciplines may not completely translate to complex palliative care settings. The heterogeneity of the palliative care population, complexity of clinical presentations, and fluctuating health states present significant research challenges. The aim of this narrative review was to explore the debate about the use of current evidence-based approaches for conducting research, such as randomized controlled trials and other study designs, in palliative care, and more specifically to (1) describe key myths about palliative care research; (2) highlight substantive challenges of conducting palliative care research, using case illustrations; and (3) propose specific strategies to address some of these challenges. Myths about research in palliative care revolve around evidence hierarchies, sample heterogeneity, random assignment, participant burden, and measurement issues. Challenges arise because of the complex physical, psychological, existential, and spiritual problems faced by patients, families, and service providers. These challenges can be organized according to six general domains: patient, system/organization, context/setting, study design, research team, and ethics. A number of approaches for dealing with challenges in conducting research fall into five separate domains: study design, sampling, conceptual, statistical, and measures and outcomes. Although randomized controlled trials have their place whenever possible, alternative designs may offer more feasible research protocols that can be successfully implemented in palliative care. Therefore, this article highlights "outside the box" approaches that would benefit both clinicians and researchers in the palliative care field. Ultimately, the selection of research designs is dependent on a clearly articulated research question, which drives the research process. Copyright © 2014 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.

Balancing selection and genetic drift at major histocompatibility complex class II genes in isolated populations of golden snub-nosed monkey (Rhinopithecus roxellana)

PubMed Central

2012-01-01

Background Small, isolated populations often experience loss of genetic variation due to random genetic drift. Unlike neutral or nearly neutral markers (such as mitochondrial genes or microsatellites), major histocompatibility complex (MHC) genes in these populations may retain high levels of polymorphism due to balancing selection. The relative roles of balancing selection and genetic drift in either small isolated or bottlenecked populations remain controversial. In this study, we examined the mechanisms maintaining polymorphisms of MHC genes in small isolated populations of the endangered golden snub-nosed monkey (Rhinopithecus roxellana) by comparing genetic variation found in MHC and microsatellite loci. There are few studies of this kind conducted on highly endangered primate species. Results Two MHC genes were sequenced and sixteen microsatellite loci were genotyped from samples representing three isolated populations. We isolated nine DQA1 alleles and sixteen DQB1 alleles and validated expression of the alleles. Lowest genetic variation for both MHC and microsatellites was found in the Shennongjia (SNJ) population. Historical balancing selection was revealed at both the DQA1 and DQB1 loci, as revealed by excess non-synonymous substitutions at antigen binding sites (ABS) and maximum-likelihood-based random-site models. Patterns of microsatellite variation revealed population structure. FST outlier analysis showed that population differentiation at the two MHC loci was similar to the microsatellite loci. Conclusions MHC genes and microsatellite loci showed the same allelic richness pattern with the lowest genetic variation occurring in SNJ, suggesting that genetic drift played a prominent role in these isolated populations. As MHC genes are subject to selective pressures, the maintenance of genetic variation is of particular interest in small, long-isolated populations. The results of this study may contribute to captive breeding and translocation programs for endangered species. PMID:23083308

Genetic Variation in the Acorn Barnacle from Allozymes to Population Genomics

PubMed Central

Flight, Patrick A.; Rand, David M.

2012-01-01

Understanding the patterns of genetic variation within and among populations is a central problem in population and evolutionary genetics. We examine this question in the acorn barnacle, Semibalanus balanoides, in which the allozyme loci Mpi and Gpi have been implicated in balancing selection due to varying selective pressures at different spatial scales. We review the patterns of genetic variation at the Mpi locus, compare this to levels of population differentiation at mtDNA and microsatellites, and place these data in the context of genome-wide variation from high-throughput sequencing of population samples spanning the North Atlantic. Despite considerable geographic variation in the patterns of selection at the Mpi allozyme, this locus shows rather low levels of population differentiation at ecological and trans-oceanic scales (FST ∼ 5%). Pooled population sequencing was performed on samples from Rhode Island (RI), Maine (ME), and Southwold, England (UK). Analysis of more than 650 million reads identified approximately 335,000 high-quality SNPs in 19 million base pairs of the S. balanoides genome. Much variation is shared across the Atlantic, but there are significant examples of strong population differentiation among samples from RI, ME, and UK. An FST outlier screen of more than 22,000 contigs provided a genome-wide context for interpretation of earlier studies on allozymes, mtDNA, and microsatellites. FST values for allozymes, mtDNA and microsatellites are close to the genome-wide average for random SNPs, with the exception of the trans-Atlantic FST for mtDNA. The majority of FST outliers were unique between individual pairs of populations, but some genes show shared patterns of excess differentiation. These data indicate that gene flow is high, that selection is strong on a subset of genes, and that a variety of genes are experiencing diversifying selection at large spatial scales. This survey of polymorphism in S. balanoides provides a number of genomic tools that promise to make this a powerful model for ecological genomics of the rocky intertidal. PMID:22767487

Effectiveness of Psychological and/or Educational Interventions in the Prevention of Anxiety: A Systematic Review, Meta-analysis, and Meta-regression.

PubMed

Moreno-Peral, Patricia; Conejo-Cerón, Sonia; Rubio-Valera, Maria; Fernández, Anna; Navas-Campaña, Desirée; Rodríguez-Morejón, Alberto; Motrico, Emma; Rigabert, Alina; Luna, Juan de Dios; Martín-Pérez, Carlos; Rodríguez-Bayón, Antonina; Ballesta-Rodríguez, María Isabel; Luciano, Juan Vicente; Bellón, Juan Ángel

2017-10-01

To our knowledge, no systematic reviews or meta-analyses have been conducted to assess the effectiveness of preventive psychological and/or educational interventions for anxiety in varied populations. To evaluate the effectiveness of preventive psychological and/or educational interventions for anxiety in varied population types. A systematic review and meta-analysis was conducted based on literature searches of MEDLINE, PsycINFO, Web of Science, EMBASE, OpenGrey, Cochrane Central Register of Controlled Trials, and other sources from inception to March 7, 2017. A search was performed of randomized clinical trials assessing the effectiveness of preventive psychological and/or educational interventions for anxiety in varying populations free of anxiety at baseline as measured using validated instruments. There was no setting or language restriction. Eligibility criteria assessment was conducted by 2 of us. Data extraction and assessment of risk of bias (Cochrane Collaboration's tool) were performed by 2 of us. Pooled standardized mean differences (SMDs) were calculated using random-effect models. Heterogeneity was explored by random-effects meta-regression. Incidence of new cases of anxiety disorders or reduction of anxiety symptoms as measured by validated instruments. Of the 3273 abstracts reviewed, 131 were selected for full-text review, and 29 met the inclusion criteria, representing 10 430 patients from 11 countries on 4 continents. Meta-analysis calculations were based on 36 comparisons. The pooled SMD was -0.31 (95% CI, -0.40 to -0.21; P < .001) and heterogeneity was substantial (I2 = 61.1%; 95% CI, 44% to 73%). There was evidence of publication bias, but the effect size barely varied after adjustment (SMD, -0.27; 95% CI, -0.37 to -0.17; P < .001). Sensitivity analyses confirmed the robustness of effect size results. A meta-regression including 5 variables explained 99.6% of between-study variability, revealing an association between higher SMD, waiting list (comparator) (β = -0.33 [95% CI, -0.55 to -0.11]; P = .005) and a lower sample size (lg) (β = 0.15 [95% CI, 0.06 to 0.23]; P = .001). No association was observed with risk of bias, family physician providing intervention, and use of standardized interviews as outcomes. Psychological and/or educational interventions had a small but statistically significant benefit for anxiety prevention in all populations evaluated. Although more studies with larger samples and active comparators are needed, these findings suggest that anxiety prevention programs should be further developed and implemented.

The impact of sample size on the reproducibility of voxel-based lesion-deficit mappings.

PubMed

Lorca-Puls, Diego L; Gajardo-Vidal, Andrea; White, Jitrachote; Seghier, Mohamed L; Leff, Alexander P; Green, David W; Crinion, Jenny T; Ludersdorfer, Philipp; Hope, Thomas M H; Bowman, Howard; Price, Cathy J

2018-07-01

This study investigated how sample size affects the reproducibility of findings from univariate voxel-based lesion-deficit analyses (e.g., voxel-based lesion-symptom mapping and voxel-based morphometry). Our effect of interest was the strength of the mapping between brain damage and speech articulation difficulties, as measured in terms of the proportion of variance explained. First, we identified a region of interest by searching on a voxel-by-voxel basis for brain areas where greater lesion load was associated with poorer speech articulation using a large sample of 360 right-handed English-speaking stroke survivors. We then randomly drew thousands of bootstrap samples from this data set that included either 30, 60, 90, 120, 180, or 360 patients. For each resample, we recorded effect size estimates and p values after conducting exactly the same lesion-deficit analysis within the previously identified region of interest and holding all procedures constant. The results show (1) how often small effect sizes in a heterogeneous population fail to be detected; (2) how effect size and its statistical significance varies with sample size; (3) how low-powered studies (due to small sample sizes) can greatly over-estimate as well as under-estimate effect sizes; and (4) how large sample sizes (N ≥ 90) can yield highly significant p values even when effect sizes are so small that they become trivial in practical terms. The implications of these findings for interpreting the results from univariate voxel-based lesion-deficit analyses are discussed. Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Unified framework to evaluate panmixia and migration direction among multiple sampling locations.

PubMed

Beerli, Peter; Palczewski, Michal

2010-05-01

For many biological investigations, groups of individuals are genetically sampled from several geographic locations. These sampling locations often do not reflect the genetic population structure. We describe a framework using marginal likelihoods to compare and order structured population models, such as testing whether the sampling locations belong to the same randomly mating population or comparing unidirectional and multidirectional gene flow models. In the context of inferences employing Markov chain Monte Carlo methods, the accuracy of the marginal likelihoods depends heavily on the approximation method used to calculate the marginal likelihood. Two methods, modified thermodynamic integration and a stabilized harmonic mean estimator, are compared. With finite Markov chain Monte Carlo run lengths, the harmonic mean estimator may not be consistent. Thermodynamic integration, in contrast, delivers considerably better estimates of the marginal likelihood. The choice of prior distributions does not influence the order and choice of the better models when the marginal likelihood is estimated using thermodynamic integration, whereas with the harmonic mean estimator the influence of the prior is pronounced and the order of the models changes. The approximation of marginal likelihood using thermodynamic integration in MIGRATE allows the evaluation of complex population genetic models, not only of whether sampling locations belong to a single panmictic population, but also of competing complex structured population models.