Methodology Series Module 5: Sampling Strategies

PubMed Central

Setia, Maninder Singh

2016-01-01

Once the research question and the research design have been finalised, it is important to select the appropriate sample for the study. The method by which the researcher selects the sample is the ‘ Sampling Method’. There are essentially two types of sampling methods: 1) probability sampling – based on chance events (such as random numbers, flipping a coin etc.); and 2) non-probability sampling – based on researcher's choice, population that accessible & available. Some of the non-probability sampling methods are: purposive sampling, convenience sampling, or quota sampling. Random sampling method (such as simple random sample or stratified random sample) is a form of probability sampling. It is important to understand the different sampling methods used in clinical studies and mention this method clearly in the manuscript. The researcher should not misrepresent the sampling method in the manuscript (such as using the term ‘ random sample’ when the researcher has used convenience sample). The sampling method will depend on the research question. For instance, the researcher may want to understand an issue in greater detail for one particular population rather than worry about the ‘ generalizability’ of these results. In such a scenario, the researcher may want to use ‘ purposive sampling’ for the study. PMID:27688438

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.

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.

Sampling Large Graphs for Anticipatory Analytics

DTIC Science & Technology

2015-05-15

low. C. Random Area Sampling Random area sampling [8] is a “ snowball ” sampling method in which a set of random seed vertices are selected and areas... Sampling Large Graphs for Anticipatory Analytics Lauren Edwards, Luke Johnson, Maja Milosavljevic, Vijay Gadepally, Benjamin A. Miller Lincoln...systems, greater human-in-the-loop involvement, or through complex algorithms. We are investigating the use of sampling to mitigate these challenges

Using maximum entropy modeling for optimal selection of sampling sites for monitoring networks

USGS Publications Warehouse

Stohlgren, Thomas J.; Kumar, Sunil; Barnett, David T.; Evangelista, Paul H.

2011-01-01

Environmental monitoring programs must efficiently describe state shifts. We propose using maximum entropy modeling to select dissimilar sampling sites to capture environmental variability at low cost, and demonstrate a specific application: sample site selection for the Central Plains domain (453,490 km2) of the National Ecological Observatory Network (NEON). We relied on four environmental factors: mean annual temperature and precipitation, elevation, and vegetation type. A “sample site” was defined as a 20 km × 20 km area (equal to NEON’s airborne observation platform [AOP] footprint), within which each 1 km2 cell was evaluated for each environmental factor. After each model run, the most environmentally dissimilar site was selected from all potential sample sites. The iterative selection of eight sites captured approximately 80% of the environmental envelope of the domain, an improvement over stratified random sampling and simple random designs for sample site selection. This approach can be widely used for cost-efficient selection of survey and monitoring sites.

1977 Survey of the American Professoriate. Technical Report.

ERIC Educational Resources Information Center

Ladd, Everett Carll, Jr.; And Others

The development and data validation of the 1977 Ladd-Lipset national survey of the American professoriate are described. The respondents were selected from a random sample of colleges and universities and from a random sample of individual faculty members from the universities. The 158 institutions in the 1977 survey were selected from 2,406…

RECAL: A Computer Program for Selecting Sample Days for Recreation Use Estimation

Treesearch

D.L. Erickson; C.J. Liu; H. Ken Cordell; W.L. Chen

1980-01-01

Recreation Calendar (RECAL) is a computer program in PL/I for drawing a sample of days for estimating recreation use. With RECAL, a sampling period of any length may be chosen; simple random, stratified random, and factorial designs can be accommodated. The program randomly allocates days to strata and locations.

Nonmanufacturing Businesses. U.S. Metric Study Interim Report.

ERIC Educational Resources Information Center

Cornog, June R.; Bunten, Elaine D.

In this fifth interim report on the feasibility of a United States changeover to a metric system stems from the U.S. Metric Study, a primary stratified sample of 2,828 nonmanufacturing firms was randomly selected from 28,184 businesses taken from Social Security files, a secondary sample of 2,258 firms was randomly selected for replacement…

The Relationship between Teachers Commitment and Female Students Academic Achievements in Some Selected Secondary School in Wolaita Zone, Southern Ethiopia

ERIC Educational Resources Information Center

Bibiso, Abyot; Olango, Menna; Bibiso, Mesfin

2017-01-01

The purpose of this study was to investigate the relationship between teacher's commitment and female students academic achievement in selected secondary school of Wolaita zone, Southern Ethiopia. The research method employed was survey study and the sampling techniques were purposive, simple random and stratified random sampling. Questionnaire…

Does self-selection affect samples' representativeness in online surveys? An investigation in online video game research.

PubMed

Khazaal, Yasser; van Singer, Mathias; Chatton, Anne; Achab, Sophia; Zullino, Daniele; Rothen, Stephane; Khan, Riaz; Billieux, Joel; Thorens, Gabriel

2014-07-07

The number of medical studies performed through online surveys has increased dramatically in recent years. Despite their numerous advantages (eg, sample size, facilitated access to individuals presenting stigmatizing issues), selection bias may exist in online surveys. However, evidence on the representativeness of self-selected samples in online studies is patchy. Our objective was to explore the representativeness of a self-selected sample of online gamers using online players' virtual characters (avatars). All avatars belonged to individuals playing World of Warcraft (WoW), currently the most widely used online game. Avatars' characteristics were defined using various games' scores, reported on the WoW's official website, and two self-selected samples from previous studies were compared with a randomly selected sample of avatars. We used scores linked to 1240 avatars (762 from the self-selected samples and 478 from the random sample). The two self-selected samples of avatars had higher scores on most of the assessed variables (except for guild membership and exploration). Furthermore, some guilds were overrepresented in the self-selected samples. Our results suggest that more proficient players or players more involved in the game may be more likely to participate in online surveys. Caution is needed in the interpretation of studies based on online surveys that used a self-selection recruitment procedure. Epidemiological evidence on the reduced representativeness of sample of online surveys is warranted.

Unbiased feature selection in learning random forests for high-dimensional data.

PubMed

Nguyen, Thanh-Tung; Huang, Joshua Zhexue; Nguyen, Thuy Thi

2015-01-01

Random forests (RFs) have been widely used as a powerful classification method. However, with the randomization in both bagging samples and feature selection, the trees in the forest tend to select uninformative features for node splitting. This makes RFs have poor accuracy when working with high-dimensional data. Besides that, RFs have bias in the feature selection process where multivalued features are favored. Aiming at debiasing feature selection in RFs, we propose a new RF algorithm, called xRF, to select good features in learning RFs for high-dimensional data. We first remove the uninformative features using p-value assessment, and the subset of unbiased features is then selected based on some statistical measures. This feature subset is then partitioned into two subsets. A feature weighting sampling technique is used to sample features from these two subsets for building trees. This approach enables one to generate more accurate trees, while allowing one to reduce dimensionality and the amount of data needed for learning RFs. An extensive set of experiments has been conducted on 47 high-dimensional real-world datasets including image datasets. The experimental results have shown that RFs with the proposed approach outperformed the existing random forests in increasing the accuracy and the AUC measures.

CTEPP STANDARD OPERATING PROCEDURE FOR SAMPLE SELECTION (SOP-1.10)

EPA Science Inventory

The procedures for selecting CTEPP study subjects are described in the SOP. The primary, county-level stratification is by region and urbanicity. Six sample counties in each of the two states (North Carolina and Ohio) are selected using stratified random sampling and reflect ...

40 CFR 761.308 - Sample selection by random number generation on any two-dimensional square grid.

Code of Federal Regulations, 2013 CFR

2013-07-01

... generation on any two-dimensional square grid. 761.308 Section 761.308 Protection of Environment... § 761.79(b)(3) § 761.308 Sample selection by random number generation on any two-dimensional square grid. (a) Divide the surface area of the non-porous surface into rectangular or square areas having a...

40 CFR 761.308 - Sample selection by random number generation on any two-dimensional square grid.

Code of Federal Regulations, 2011 CFR

2011-07-01

... generation on any two-dimensional square grid. 761.308 Section 761.308 Protection of Environment... § 761.79(b)(3) § 761.308 Sample selection by random number generation on any two-dimensional square grid. (a) Divide the surface area of the non-porous surface into rectangular or square areas having a...

40 CFR 761.308 - Sample selection by random number generation on any two-dimensional square grid.

Code of Federal Regulations, 2010 CFR

2010-07-01

... generation on any two-dimensional square grid. 761.308 Section 761.308 Protection of Environment... § 761.79(b)(3) § 761.308 Sample selection by random number generation on any two-dimensional square grid. (a) Divide the surface area of the non-porous surface into rectangular or square areas having a...

40 CFR 761.308 - Sample selection by random number generation on any two-dimensional square grid.

Code of Federal Regulations, 2014 CFR

2014-07-01

... generation on any two-dimensional square grid. 761.308 Section 761.308 Protection of Environment... § 761.79(b)(3) § 761.308 Sample selection by random number generation on any two-dimensional square grid. (a) Divide the surface area of the non-porous surface into rectangular or square areas having a...

40 CFR 761.308 - Sample selection by random number generation on any two-dimensional square grid.

Code of Federal Regulations, 2012 CFR

2012-07-01

... generation on any two-dimensional square grid. 761.308 Section 761.308 Protection of Environment... § 761.79(b)(3) § 761.308 Sample selection by random number generation on any two-dimensional square grid. (a) Divide the surface area of the non-porous surface into rectangular or square areas having a...

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.

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.

Final report : sampling plan for pavement condition ratings of secondary roads.

DOT National Transportation Integrated Search

1984-01-01

The purpose of this project was to develop a random sampling plan for use in selecting segments of the secondary highway system for evaluation under the Department's PMS. The plan developed is described here. It is a simple, workable, random sampling...

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...

Avoid Early Selection for Growth Rate in Cottonwood

Treesearch

D. T. Cooper; Robert B. Ferguson

1971-01-01

A sample of 37 cottonwood clones from a selection program was compared with a sample of 40 random clones in a 14-year test at two sites near Stoneville, Mississippi. Throughout the test period, the select sample was slightly better in mean growth rate, but this difference decreased with age. Performance of ''blue tag" clones selected at age 5 and planted...

Does Self-Selection Affect Samples’ Representativeness in Online Surveys? An Investigation in Online Video Game Research

PubMed Central

van Singer, Mathias; Chatton, Anne; Achab, Sophia; Zullino, Daniele; Rothen, Stephane; Khan, Riaz; Billieux, Joel; Thorens, Gabriel

2014-01-01

Background The number of medical studies performed through online surveys has increased dramatically in recent years. Despite their numerous advantages (eg, sample size, facilitated access to individuals presenting stigmatizing issues), selection bias may exist in online surveys. However, evidence on the representativeness of self-selected samples in online studies is patchy. Objective Our objective was to explore the representativeness of a self-selected sample of online gamers using online players’ virtual characters (avatars). Methods All avatars belonged to individuals playing World of Warcraft (WoW), currently the most widely used online game. Avatars’ characteristics were defined using various games’ scores, reported on the WoW’s official website, and two self-selected samples from previous studies were compared with a randomly selected sample of avatars. Results We used scores linked to 1240 avatars (762 from the self-selected samples and 478 from the random sample). The two self-selected samples of avatars had higher scores on most of the assessed variables (except for guild membership and exploration). Furthermore, some guilds were overrepresented in the self-selected samples. Conclusions Our results suggest that more proficient players or players more involved in the game may be more likely to participate in online surveys. Caution is needed in the interpretation of studies based on online surveys that used a self-selection recruitment procedure. Epidemiological evidence on the reduced representativeness of sample of online surveys is warranted. PMID:25001007

The coalescent of a sample from a binary branching process.

PubMed

Lambert, Amaury

2018-04-25

At time 0, start a time-continuous binary branching process, where particles give birth to a single particle independently (at a possibly time-dependent rate) and die independently (at a possibly time-dependent and age-dependent rate). A particular case is the classical birth-death process. Stop this process at time T>0. It is known that the tree spanned by the N tips alive at time T of the tree thus obtained (called a reduced tree or coalescent tree) is a coalescent point process (CPP), which basically means that the depths of interior nodes are independent and identically distributed (iid). Now select each of the N tips independently with probability y (Bernoulli sample). It is known that the tree generated by the selected tips, which we will call the Bernoulli sampled CPP, is again a CPP. Now instead, select exactly k tips uniformly at random among the N tips (a k-sample). We show that the tree generated by the selected tips is a mixture of Bernoulli sampled CPPs with the same parent CPP, over some explicit distribution of the sampling probability y. An immediate consequence is that the genealogy of a k-sample can be obtained by the realization of k random variables, first the random sampling probability Y and then the k-1 node depths which are iid conditional on Y=y. Copyright © 2018. Published by Elsevier Inc.

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

Use of Matrix Sampling Procedures to Assess Achievement in Solving Open Addition and Subtraction Sentences.

ERIC Educational Resources Information Center

Montague, Margariete A.

This study investigated the feasibility of concurrently and randomly sampling examinees and items in order to estimate group achievement. Seven 32-item tests reflecting a 640-item universe of simple open sentences were used such that item selection (random, systematic) and assignment (random, systematic) of items (four, eight, sixteen) to forms…

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…

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

Estimating the efficacy of Alcoholics Anonymous without self-selection bias: An instrumental variables re-analysis of randomized clinical trials

PubMed Central

Humphreys, Keith; Blodgett, Janet C.; Wagner, Todd H.

2014-01-01

Background Observational studies of Alcoholics Anonymous’ (AA) effectiveness are vulnerable to self-selection bias because individuals choose whether or not to attend AA. The present study therefore employed an innovative statistical technique to derive a selection bias-free estimate of AA’s impact. Methods Six datasets from 5 National Institutes of Health-funded randomized trials (one with two independent parallel arms) of AA facilitation interventions were analyzed using instrumental variables models. Alcohol dependent individuals in one of the datasets (n = 774) were analyzed separately from the rest of sample (n = 1582 individuals pooled from 5 datasets) because of heterogeneity in sample parameters. Randomization itself was used as the instrumental variable. Results Randomization was a good instrument in both samples, effectively predicting increased AA attendance that could not be attributed to self-selection. In five of the six data sets, which were pooled for analysis, increased AA attendance that was attributable to randomization (i.e., free of self-selection bias) was effective at increasing days of abstinence at 3-month (B = .38, p = .001) and 15-month (B = 0.42, p = .04) follow-up. However, in the remaining dataset, in which pre-existing AA attendance was much higher, further increases in AA involvement caused by the randomly assigned facilitation intervention did not affect drinking outcome. Conclusions For most individuals seeking help for alcohol problems, increasing AA attendance leads to short and long term decreases in alcohol consumption that cannot be attributed to self-selection. However, for populations with high pre-existing AA involvement, further increases in AA attendance may have little impact. PMID:25421504

Estimating the efficacy of Alcoholics Anonymous without self-selection bias: an instrumental variables re-analysis of randomized clinical trials.

PubMed

Humphreys, Keith; Blodgett, Janet C; Wagner, Todd H

2014-11-01

Observational studies of Alcoholics Anonymous' (AA) effectiveness are vulnerable to self-selection bias because individuals choose whether or not to attend AA. The present study, therefore, employed an innovative statistical technique to derive a selection bias-free estimate of AA's impact. Six data sets from 5 National Institutes of Health-funded randomized trials (1 with 2 independent parallel arms) of AA facilitation interventions were analyzed using instrumental variables models. Alcohol-dependent individuals in one of the data sets (n = 774) were analyzed separately from the rest of sample (n = 1,582 individuals pooled from 5 data sets) because of heterogeneity in sample parameters. Randomization itself was used as the instrumental variable. Randomization was a good instrument in both samples, effectively predicting increased AA attendance that could not be attributed to self-selection. In 5 of the 6 data sets, which were pooled for analysis, increased AA attendance that was attributable to randomization (i.e., free of self-selection bias) was effective at increasing days of abstinence at 3-month (B = 0.38, p = 0.001) and 15-month (B = 0.42, p = 0.04) follow-up. However, in the remaining data set, in which preexisting AA attendance was much higher, further increases in AA involvement caused by the randomly assigned facilitation intervention did not affect drinking outcome. For most individuals seeking help for alcohol problems, increasing AA attendance leads to short- and long-term decreases in alcohol consumption that cannot be attributed to self-selection. However, for populations with high preexisting AA involvement, further increases in AA attendance may have little impact. Copyright © 2014 by the Research Society on Alcoholism.

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.

Performance of Random Effects Model Estimators under Complex Sampling Designs

ERIC Educational Resources Information Center

Jia, Yue; Stokes, Lynne; Harris, Ian; Wang, Yan

2011-01-01

In this article, we consider estimation of parameters of random effects models from samples collected via complex multistage designs. Incorporation of sampling weights is one way to reduce estimation bias due to unequal probabilities of selection. Several weighting methods have been proposed in the literature for estimating the parameters of…

THREE-PEE SAMPLING THEORY and program 'THRP' for computer generation of selection criteria

Treesearch

L. R. Grosenbaugh

1965-01-01

Theory necessary for sampling with probability proportional to prediction ('three-pee,' or '3P,' sampling) is first developed and then exemplified by numerical comparisons of several estimators. Program 'T RP' for computer generation of appropriate 3P-sample-selection criteria is described, and convenient random integer dispensers are...

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.

A new mosaic method for three-dimensional surface

NASA Astrophysics Data System (ADS)

Yuan, Yun; Zhu, Zhaokun; Ding, Yongjun

2011-08-01

Three-dimensional (3-D) data mosaic is a indispensable link in surface measurement and digital terrain map generation. With respect to the mosaic problem of the local unorganized cloud points with rude registration and mass mismatched points, a new mosaic method for 3-D surface based on RANSAC is proposed. Every circular of this method is processed sequentially by random sample with additional shape constraint, data normalization of cloud points, absolute orientation, data denormalization of cloud points, inlier number statistic, etc. After N random sample trials the largest consensus set is selected, and at last the model is re-estimated using all the points in the selected subset. The minimal subset is composed of three non-colinear points which form a triangle. The shape of triangle is considered in random sample selection in order to make the sample selection reasonable. A new coordinate system transformation algorithm presented in this paper is used to avoid the singularity. The whole rotation transformation between the two coordinate systems can be solved by twice rotations expressed by Euler angle vector, each rotation has explicit physical means. Both simulation and real data are used to prove the correctness and validity of this mosaic method. This method has better noise immunity due to its robust estimation property, and has high accuracy as the shape constraint is added to random sample and the data normalization added to the absolute orientation. This method is applicable for high precision measurement of three-dimensional surface and also for the 3-D terrain mosaic.

Optimized probability sampling of study sites to improve generalizability in a multisite intervention trial.

PubMed

Kraschnewski, Jennifer L; Keyserling, Thomas C; Bangdiwala, Shrikant I; Gizlice, Ziya; Garcia, Beverly A; Johnston, Larry F; Gustafson, Alison; Petrovic, Lindsay; Glasgow, Russell E; Samuel-Hodge, Carmen D

2010-01-01

Studies of type 2 translation, the adaption of evidence-based interventions to real-world settings, should include representative study sites and staff to improve external validity. Sites for such studies are, however, often selected by convenience sampling, which limits generalizability. We used an optimized probability sampling protocol to select an unbiased, representative sample of study sites to prepare for a randomized trial of a weight loss intervention. We invited North Carolina health departments within 200 miles of the research center to participate (N = 81). Of the 43 health departments that were eligible, 30 were interested in participating. To select a representative and feasible sample of 6 health departments that met inclusion criteria, we generated all combinations of 6 from the 30 health departments that were eligible and interested. From the subset of combinations that met inclusion criteria, we selected 1 at random. Of 593,775 possible combinations of 6 counties, 15,177 (3%) met inclusion criteria. Sites in the selected subset were similar to all eligible sites in terms of health department characteristics and county demographics. Optimized probability sampling improved generalizability by ensuring an unbiased and representative sample of study sites.

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…

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.

Effects of Sample Selection on Estimates of Economic Impacts of Outdoor Recreation

Treesearch

Donald B.K. English

1997-01-01

Estimates of the economic impacts of recreation often come from spending data provided by a self-selected subset of a random sample of site visitors. The subset is frequently less than half the onsite sample. Biased vectors of per trip spending and impact estimates can result if self-selection is related to spending pattctns, and proper corrective procedures arc not...

Resource Input, Service Process and Resident Activity Indicators in a Welsh National Random Sample of Staffed Housing Services for People with Intellectual Disabilities

ERIC Educational Resources Information Center

Felce, David; Perry, Jonathan

2004-01-01

Background: The aims were to: (i) explore the association between age and size of setting and staffing per resident; and (ii) report resident and setting characteristics, and indicators of service process and resident activity for a national random sample of staffed housing provision. Methods: Sixty settings were selected randomly from those…

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…

Statistical methods for efficient design of community surveys of response to noise: Random coefficients regression models

NASA Technical Reports Server (NTRS)

Tomberlin, T. J.

1985-01-01

Research studies of residents' responses to noise consist of interviews with samples of individuals who are drawn from a number of different compact study areas. The statistical techniques developed provide a basis for those sample design decisions. These techniques are suitable for a wide range of sample survey applications. A sample may consist of a random sample of residents selected from a sample of compact study areas, or in a more complex design, of a sample of residents selected from a sample of larger areas (e.g., cities). The techniques may be applied to estimates of the effects on annoyance of noise level, numbers of noise events, the time-of-day of the events, ambient noise levels, or other factors. Methods are provided for determining, in advance, how accurately these effects can be estimated for different sample sizes and study designs. Using a simple cost function, they also provide for optimum allocation of the sample across the stages of the design for estimating these effects. These techniques are developed via a regression model in which the regression coefficients are assumed to be random, with components of variance associated with the various stages of a multi-stage sample design.

The Effects of Total Physical Response by Storytelling and the Traditional Teaching Styles of a Foreign Language in a Selected High School

ERIC Educational Resources Information Center

Kariuki, Patrick N. K.; Bush, Elizabeth Danielle

2008-01-01

The purpose of this study was to examine the effects of Total Physical Response by Storytelling and the traditional teaching method on a foreign language in a selected high school. The sample consisted of 30 students who were randomly selected and randomly assigned to experimental and control group. The experimental group was taught using Total…

Eating and Exercising: Nebraska Adolescents' Attitudes and Behaviors. Technical Report 25.

ERIC Educational Resources Information Center

Newman, Ian M.

This report describes selected eating and exercise patterns among a sample of 2,237 Nebraska youth in grades 9-12 selected from a random sample of 24 junior and senior high schools. The eating patterns reported cover food selection, body image, weight management, and weight loss methods. The exercise patterns relate to the frequency of…

Random forests ensemble classifier trained with data resampling strategy to improve cardiac arrhythmia diagnosis.

PubMed

Ozçift, Akin

2011-05-01

Supervised classification algorithms are commonly used in the designing of computer-aided diagnosis systems. In this study, we present a resampling strategy based Random Forests (RF) ensemble classifier to improve diagnosis of cardiac arrhythmia. Random forests is an ensemble classifier that consists of many decision trees and outputs the class that is the mode of the class's output by individual trees. In this way, an RF ensemble classifier performs better than a single tree from classification performance point of view. In general, multiclass datasets having unbalanced distribution of sample sizes are difficult to analyze in terms of class discrimination. Cardiac arrhythmia is such a dataset that has multiple classes with small sample sizes and it is therefore adequate to test our resampling based training strategy. The dataset contains 452 samples in fourteen types of arrhythmias and eleven of these classes have sample sizes less than 15. Our diagnosis strategy consists of two parts: (i) a correlation based feature selection algorithm is used to select relevant features from cardiac arrhythmia dataset. (ii) RF machine learning algorithm is used to evaluate the performance of selected features with and without simple random sampling to evaluate the efficiency of proposed training strategy. The resultant accuracy of the classifier is found to be 90.0% and this is a quite high diagnosis performance for cardiac arrhythmia. Furthermore, three case studies, i.e., thyroid, cardiotocography and audiology, are used to benchmark the effectiveness of the proposed method. The results of experiments demonstrated the efficiency of random sampling strategy in training RF ensemble classification algorithm. Copyright © 2011 Elsevier Ltd. All rights reserved.

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.

Analysis of training sample selection strategies for regression-based quantitative landslide susceptibility mapping methods

NASA Astrophysics Data System (ADS)

Erener, Arzu; Sivas, A. Abdullah; Selcuk-Kestel, A. Sevtap; Düzgün, H. Sebnem

2017-07-01

All of the quantitative landslide susceptibility mapping (QLSM) methods requires two basic data types, namely, landslide inventory and factors that influence landslide occurrence (landslide influencing factors, LIF). Depending on type of landslides, nature of triggers and LIF, accuracy of the QLSM methods differs. Moreover, how to balance the number of 0 (nonoccurrence) and 1 (occurrence) in the training set obtained from the landslide inventory and how to select which one of the 1's and 0's to be included in QLSM models play critical role in the accuracy of the QLSM. Although performance of various QLSM methods is largely investigated in the literature, the challenge of training set construction is not adequately investigated for the QLSM methods. In order to tackle this challenge, in this study three different training set selection strategies along with the original data set is used for testing the performance of three different regression methods namely Logistic Regression (LR), Bayesian Logistic Regression (BLR) and Fuzzy Logistic Regression (FLR). The first sampling strategy is proportional random sampling (PRS), which takes into account a weighted selection of landslide occurrences in the sample set. The second method, namely non-selective nearby sampling (NNS), includes randomly selected sites and their surrounding neighboring points at certain preselected distances to include the impact of clustering. Selective nearby sampling (SNS) is the third method, which concentrates on the group of 1's and their surrounding neighborhood. A randomly selected group of landslide sites and their neighborhood are considered in the analyses similar to NNS parameters. It is found that LR-PRS, FLR-PRS and BLR-Whole Data set-ups, with order, yield the best fits among the other alternatives. The results indicate that in QLSM based on regression models, avoidance of spatial correlation in the data set is critical for the model's performance.

Emotional Intelligence and Life Adjustment for Nigerian Secondary Students

ERIC Educational Resources Information Center

Ogoemeka, Obioma Helen

2013-01-01

In the process of educating adolescents, good emotional development and life adjustment are two significant factors for teachers to know. This study employed random cluster sampling of senior secondary school students in Ondo and Oyo States in south-western Nigeria. The Random sampling was employed to select 1,070 students. The data collected were…

[Comparison study on sampling methods of Oncomelania hupensis snail survey in marshland schistosomiasis epidemic areas in China].

PubMed

An, Zhao; Wen-Xin, Zhang; Zhong, Yao; Yu-Kuan, Ma; Qing, Liu; Hou-Lang, Duan; Yi-di, Shang

2016-06-29

To optimize and simplify the survey method of Oncomelania hupensis snail in marshland endemic region of schistosomiasis and increase the precision, efficiency and economy of the snail survey. A quadrate experimental field was selected as the subject of 50 m×50 m size in Chayegang marshland near Henghu farm in the Poyang Lake region and a whole-covered method was adopted to survey the snails. The simple random sampling, systematic sampling and stratified random sampling methods were applied to calculate the minimum sample size, relative sampling error and absolute sampling error. The minimum sample sizes of the simple random sampling, systematic sampling and stratified random sampling methods were 300, 300 and 225, respectively. The relative sampling errors of three methods were all less than 15%. The absolute sampling errors were 0.221 7, 0.302 4 and 0.047 8, respectively. The spatial stratified sampling with altitude as the stratum variable is an efficient approach of lower cost and higher precision for the snail survey.

TOC: Table of Contents Practices of Primary Journals--Recommendations for Monolingual, Multilingual and International Journals.

ERIC Educational Resources Information Center

Juhasz, Stephen; And Others

Table of contents (TOC) practices of some 120 primary journals were analyzed. The journals were randomly selected. The method of randomization is described. The samples were selected from a university library with a holding of approximately 12,000 titles published worldwide. A questionnaire was designed. Purpose was to find uniformity and…

Provider-related barriers to rapid HIV testing in U.S. urban non-profit community clinics, community-based organizations (CBOs) and hospitals.

PubMed

Bogart, Laura M; Howerton, Devery; Lange, James; Setodji, Claude Messan; Becker, Kirsten; Klein, David J; Asch, Steven M

2010-06-01

We examined provider-reported barriers to rapid HIV testing in U.S. urban non-profit community clinics, community-based organizations (CBOs), and hospitals. 12 primary metropolitan statistical areas (PMSAs; three per region) were sampled randomly, with sampling weights proportional to AIDS case reports. Across PMSAs, all 671 hospitals and a random sample of 738 clinics/CBOs were telephoned for a survey on rapid HIV test availability. Of the 671 hospitals, 172 hospitals were randomly selected for barriers questions, for which 158 laboratory and 136 department staff were eligible and interviewed in 2005. Of the 738 clinics/CBOs, 276 were randomly selected for barriers questions, 206 were reached, and 118 were eligible and interviewed in 2005-2006. In multivariate models, barriers regarding translation of administrative/quality assurance policies into practice were significantly associated with rapid HIV testing availability. For greater rapid testing diffusion, policies are needed to reduce administrative barriers and provide quality assurance training to non-laboratory staff.

Attitudes towards smoking restrictions and tobacco advertisement bans in Georgia.

PubMed

Bakhturidze, George D; Mittelmark, Maurice B; Aarø, Leif E; Peikrishvili, Nana T

2013-11-25

This study aims to provide data on a public level of support for restricting smoking in public places and banning tobacco advertisements. A nationally representative multistage sampling design, with sampling strata defined by region (sampling quotas proportional to size) and substrata defined by urban/rural and mountainous/lowland settlement, within which census enumeration districts were randomly sampled, within which households were randomly sampled, within which a randomly selected respondent was interviewed. The country of Georgia, population 4.7 million, located in the Caucasus region of Eurasia. One household member aged between 13 and 70 was selected as interviewee. In households with more than one age-eligible person, selection was carried out at random. Of 1588 persons selected, 14 refused to participate and interviews were conducted with 915 women and 659 men. Respondents were interviewed about their level of agreement with eight possible smoking restrictions/bans, used to calculate a single dichotomous (agree/do not agree) opinion indicator. The level of agreement with restrictions was analysed in bivariate and multivariate analyses by age, gender, education, income and tobacco use status. Overall, 84.9% of respondents indicated support for smoking restrictions and tobacco advertisement bans. In all demographic segments, including tobacco users, the majority of respondents indicated agreement with restrictions, ranging from a low of 51% in the 13-25 age group to a high of 98% in the 56-70 age group. Logistic regression with all demographic variables entered showed that agreement with restrictions was higher with age, and was significantly higher among never smokers as compared to daily smokers. Georgian public opinion is normatively supportive of more stringent tobacco-control measures in the form of smoking restrictions and tobacco advertisement bans.

The Effect of Departmentalization on the Reading Achievement of Sixth-Grade Students.

ERIC Educational Resources Information Center

Harris, Mary B.

A study examined whether departmentalization affected the reading achievement of sixth-grade students attending a Chicago public school. A random sample of 30 students was chosen from a group of 53 who received instruction in a departmentalized program. A second random sample of 30 was selected from a total of 54 students who received instruction…

The Evaluation of Bias of the Weighted Random Effects Model Estimators. Research Report. ETS RR-11-13

ERIC Educational Resources Information Center

Jia, Yue; Stokes, Lynne; Harris, Ian; Wang, Yan

2011-01-01

Estimation of parameters of random effects models from samples collected via complex multistage designs is considered. One way to reduce estimation bias due to unequal probabilities of selection is to incorporate sampling weights. Many researchers have been proposed various weighting methods (Korn, & Graubard, 2003; Pfeffermann, Skinner,…

A management-oriented classification of pinyon-juniper woodlands of the Great Basin

Treesearch

Neil E. West; Robin J. Tausch; Paul T. Tueller

1998-01-01

A hierarchical framework for the classification of Great Basin pinyon-juniper woodlands was based on a systematic sample of 426 stands from a random selection of 66 of the 110 mountain ranges in the region. That is, mountain ranges were randomly selected, but stands were systematically located on mountain ranges. The National Hierarchical Framework of Ecological Units...

Accelerating IMRT optimization by voxel sampling

NASA Astrophysics Data System (ADS)

Martin, Benjamin C.; Bortfeld, Thomas R.; Castañon, David A.

2007-12-01

This paper presents a new method for accelerating intensity-modulated radiation therapy (IMRT) optimization using voxel sampling. Rather than calculating the dose to the entire patient at each step in the optimization, the dose is only calculated for some randomly selected voxels. Those voxels are then used to calculate estimates of the objective and gradient which are used in a randomized version of a steepest descent algorithm. By selecting different voxels on each step, we are able to find an optimal solution to the full problem. We also present an algorithm to automatically choose the best sampling rate for each structure within the patient during the optimization. Seeking further improvements, we experimented with several other gradient-based optimization algorithms and found that the delta-bar-delta algorithm performs well despite the randomness. Overall, we were able to achieve approximately an order of magnitude speedup on our test case as compared to steepest descent.

Random sampling of elementary flux modes in large-scale metabolic networks.

PubMed

Machado, Daniel; Soons, Zita; Patil, Kiran Raosaheb; Ferreira, Eugénio C; Rocha, Isabel

2012-09-15

The description of a metabolic network in terms of elementary (flux) modes (EMs) provides an important framework for metabolic pathway analysis. However, their application to large networks has been hampered by the combinatorial explosion in the number of modes. In this work, we develop a method for generating random samples of EMs without computing the whole set. Our algorithm is an adaptation of the canonical basis approach, where we add an additional filtering step which, at each iteration, selects a random subset of the new combinations of modes. In order to obtain an unbiased sample, all candidates are assigned the same probability of getting selected. This approach avoids the exponential growth of the number of modes during computation, thus generating a random sample of the complete set of EMs within reasonable time. We generated samples of different sizes for a metabolic network of Escherichia coli, and observed that they preserve several properties of the full EM set. It is also shown that EM sampling can be used for rational strain design. A well distributed sample, that is representative of the complete set of EMs, should be suitable to most EM-based methods for analysis and optimization of metabolic networks. Source code for a cross-platform implementation in Python is freely available at http://code.google.com/p/emsampler. dmachado@deb.uminho.pt Supplementary data are available at Bioinformatics online.

[Study on correction of data bias caused by different missing mechanisms in survey of medical expenditure among students enrolling in Urban Resident Basic Medical Insurance].

PubMed

Zhang, Haixia; Zhao, Junkang; Gu, Caijiao; Cui, Yan; Rong, Huiying; Meng, Fanlong; Wang, Tong

2015-05-01

The study of the medical expenditure and its influencing factors among the students enrolling in Urban Resident Basic Medical Insurance (URBMI) in Taiyuan indicated that non response bias and selection bias coexist in dependent variable of the survey data. Unlike previous studies only focused on one missing mechanism, a two-stage method to deal with two missing mechanisms simultaneously was suggested in this study, combining multiple imputation with sample selection model. A total of 1 190 questionnaires were returned by the students (or their parents) selected in child care settings, schools and universities in Taiyuan by stratified cluster random sampling in 2012. In the returned questionnaires, 2.52% existed not missing at random (NMAR) of dependent variable and 7.14% existed missing at random (MAR) of dependent variable. First, multiple imputation was conducted for MAR by using completed data, then sample selection model was used to correct NMAR in multiple imputation, and a multi influencing factor analysis model was established. Based on 1 000 times resampling, the best scheme of filling the random missing values is the predictive mean matching (PMM) method under the missing proportion. With this optimal scheme, a two stage survey was conducted. Finally, it was found that the influencing factors on annual medical expenditure among the students enrolling in URBMI in Taiyuan included population group, annual household gross income, affordability of medical insurance expenditure, chronic disease, seeking medical care in hospital, seeking medical care in community health center or private clinic, hospitalization, hospitalization canceled due to certain reason, self medication and acceptable proportion of self-paid medical expenditure. The two-stage method combining multiple imputation with sample selection model can deal with non response bias and selection bias effectively in dependent variable of the survey data.

Validity and Reliability of Psychosocial Factors Related to Breast Cancer Screening.

ERIC Educational Resources Information Center

Zapka, Jane G.; And Others

1991-01-01

The construct validity of hypothesized survey items and data reduction procedures for selected psychosocial constructs frequently used in breast cancer screening research were investigated in telephone interviews with randomly selected samples of 1,184 and 903 women and a sample of 169 Hispanic clinic clients. Validity of the constructs is…

Attenders versus Slackers: A Classroom Demonstration of Quasi-Experimentation and Self-Selecting Samples

ERIC Educational Resources Information Center

Stellmack, Mark A.

2013-01-01

Studies of the effects of class attendance on class performance typically are quasi-experimental because students choose whether or not to attend class; that is, the samples are self-selecting. The lack of random assignment prevents one from establishing a causal relationship between attendance and performance. Relating attendance to performance…

Teachers' Methodologies and Sources of Information on HIV/AIDS for Students with Visual Impairments in Selected Residential and Integrated Schools in Ghana

ERIC Educational Resources Information Center

Hayford, Samuel K.; Ocansey, Frederick

2017-01-01

This study reports part of a national survey on sources of information, education and communication materials on HIV/AIDS available to students with visual impairments in residential, segregated, and integrated schools in Ghana. A multi-staged stratified random sampling procedure and a purposive and simple random sampling approach, where…

Modeling of Academic Achievement of Primary School Students in Ethiopia Using Bayesian Multilevel Approach

ERIC Educational Resources Information Center

Sebro, Negusse Yohannes; Goshu, Ayele Taye

2017-01-01

This study aims to explore Bayesian multilevel modeling to investigate variations of average academic achievement of grade eight school students. A sample of 636 students is randomly selected from 26 private and government schools by a two-stage stratified sampling design. Bayesian method is used to estimate the fixed and random effects. Input and…

Reweighting of the primary sampling units in the National Automotive Sampling System

DOT National Transportation Integrated Search

1997-09-01

The original design of hte National Automotive Sampling System - formerly the National Accident Sampling System - called for 75 PSUs randomly selected from PSUs which were grouped into various strata across the U.S. The implementation of the PSU samp...

Ensemble Feature Learning of Genomic Data Using Support Vector Machine

PubMed Central

Anaissi, Ali; Goyal, Madhu; Catchpoole, Daniel R.; Braytee, Ali; Kennedy, Paul J.

2016-01-01

The identification of a subset of genes having the ability to capture the necessary information to distinguish classes of patients is crucial in bioinformatics applications. Ensemble and bagging methods have been shown to work effectively in the process of gene selection and classification. Testament to that is random forest which combines random decision trees with bagging to improve overall feature selection and classification accuracy. Surprisingly, the adoption of these methods in support vector machines has only recently received attention but mostly on classification not gene selection. This paper introduces an ensemble SVM-Recursive Feature Elimination (ESVM-RFE) for gene selection that follows the concepts of ensemble and bagging used in random forest but adopts the backward elimination strategy which is the rationale of RFE algorithm. The rationale behind this is, building ensemble SVM models using randomly drawn bootstrap samples from the training set, will produce different feature rankings which will be subsequently aggregated as one feature ranking. As a result, the decision for elimination of features is based upon the ranking of multiple SVM models instead of choosing one particular model. Moreover, this approach will address the problem of imbalanced datasets by constructing a nearly balanced bootstrap sample. Our experiments show that ESVM-RFE for gene selection substantially increased the classification performance on five microarray datasets compared to state-of-the-art methods. Experiments on the childhood leukaemia dataset show that an average 9% better accuracy is achieved by ESVM-RFE over SVM-RFE, and 5% over random forest based approach. The selected genes by the ESVM-RFE algorithm were further explored with Singular Value Decomposition (SVD) which reveals significant clusters with the selected data. PMID:27304923

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

The use of single-date MODIS imagery for estimating large-scale urban impervious surface fraction with spectral mixture analysis and machine learning techniques

NASA Astrophysics Data System (ADS)

Deng, Chengbin; Wu, Changshan

2013-12-01

Urban impervious surface information is essential for urban and environmental applications at the regional/national scales. As a popular image processing technique, spectral mixture analysis (SMA) has rarely been applied to coarse-resolution imagery due to the difficulty of deriving endmember spectra using traditional endmember selection methods, particularly within heterogeneous urban environments. To address this problem, we derived endmember signatures through a least squares solution (LSS) technique with known abundances of sample pixels, and integrated these endmember signatures into SMA for mapping large-scale impervious surface fraction. In addition, with the same sample set, we carried out objective comparative analyses among SMA (i.e. fully constrained and unconstrained SMA) and machine learning (i.e. Cubist regression tree and Random Forests) techniques. Analysis of results suggests three major conclusions. First, with the extrapolated endmember spectra from stratified random training samples, the SMA approaches performed relatively well, as indicated by small MAE values. Second, Random Forests yields more reliable results than Cubist regression tree, and its accuracy is improved with increased sample sizes. Finally, comparative analyses suggest a tentative guide for selecting an optimal approach for large-scale fractional imperviousness estimation: unconstrained SMA might be a favorable option with a small number of samples, while Random Forests might be preferred if a large number of samples are available.

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.

Reducing seed dependent variability of non-uniformly sampled multidimensional NMR data

NASA Astrophysics Data System (ADS)

Mobli, Mehdi

2015-07-01

The application of NMR spectroscopy to study the structure, dynamics and function of macromolecules requires the acquisition of several multidimensional spectra. The one-dimensional NMR time-response from the spectrometer is extended to additional dimensions by introducing incremented delays in the experiment that cause oscillation of the signal along "indirect" dimensions. For a given dimension the delay is incremented at twice the rate of the maximum frequency (Nyquist rate). To achieve high-resolution requires acquisition of long data records sampled at the Nyquist rate. This is typically a prohibitive step due to time constraints, resulting in sub-optimal data records to the detriment of subsequent analyses. The multidimensional NMR spectrum itself is typically sparse, and it has been shown that in such cases it is possible to use non-Fourier methods to reconstruct a high-resolution multidimensional spectrum from a random subset of non-uniformly sampled (NUS) data. For a given acquisition time, NUS has the potential to improve the sensitivity and resolution of a multidimensional spectrum, compared to traditional uniform sampling. The improvements in sensitivity and/or resolution achieved by NUS are heavily dependent on the distribution of points in the random subset acquired. Typically, random points are selected from a probability density function (PDF) weighted according to the NMR signal envelope. In extreme cases as little as 1% of the data is subsampled. The heavy under-sampling can result in poor reproducibility, i.e. when two experiments are carried out where the same number of random samples is selected from the same PDF but using different random seeds. Here, a jittered sampling approach is introduced that is shown to improve random seed dependent reproducibility of multidimensional spectra generated from NUS data, compared to commonly applied NUS methods. It is shown that this is achieved due to the low variability of the inherent sensitivity of the random subset chosen from a given PDF. Finally, it is demonstrated that metrics used to find optimal NUS distributions are heavily dependent on the inherent sensitivity of the random subset, and such optimisation is therefore less critical when using the proposed sampling scheme.

Species conservation profiles of a random sample of world spiders I: Agelenidae to Filistatidae

PubMed Central

Seppälä, Sini; Henriques, Sérgio; Draney, Michael L; Foord, Stefan; Gibbons, Alastair T; Gomez, Luz A; Kariko, Sarah; Malumbres-Olarte, Jagoba; Milne, Marc; Vink, Cor J

2018-01-01

Abstract Background The IUCN Red List of Threatened Species is the most widely used information source on the extinction risk of species. One of the uses of the Red List is to evaluate and monitor the state of biodiversity and a possible approach for this purpose is the Red List Index (RLI). For many taxa, mainly hyperdiverse groups, it is not possible within available resources to assess all known species. In such cases, a random sample of species might be selected for assessment and the results derived from it extrapolated for the entire group - the Sampled Red List Index (SRLI). With the current contribution and the three following papers, we intend to create the first point in time of a future spider SRLI encompassing 200 species distributed across the world. New information A sample of 200 species of spiders were randomly selected from the World Spider Catalogue, an updated global database containing all recognised species names for the group. The 200 selected species where divided taxonomically at the family level and the familes were ordered alphabetically. In this publication, we present the conservation profiles of 46 species belonging to the famillies alphabetically arranged between Agelenidae and Filistatidae, which encompassed Agelenidae, Amaurobiidae, Anyphaenidae, Araneidae, Archaeidae, Barychelidae, Clubionidae, Corinnidae, Ctenidae, Ctenizidae, Cyatholipidae, Dictynidae, Dysderidae, Eresidae and Filistatidae. PMID:29725239

Species conservation profiles of a random sample of world spiders I: Agelenidae to Filistatidae.

PubMed

Seppälä, Sini; Henriques, Sérgio; Draney, Michael L; Foord, Stefan; Gibbons, Alastair T; Gomez, Luz A; Kariko, Sarah; Malumbres-Olarte, Jagoba; Milne, Marc; Vink, Cor J; Cardoso, Pedro

2018-01-01

The IUCN Red List of Threatened Species is the most widely used information source on the extinction risk of species. One of the uses of the Red List is to evaluate and monitor the state of biodiversity and a possible approach for this purpose is the Red List Index (RLI). For many taxa, mainly hyperdiverse groups, it is not possible within available resources to assess all known species. In such cases, a random sample of species might be selected for assessment and the results derived from it extrapolated for the entire group - the Sampled Red List Index (SRLI). With the current contribution and the three following papers, we intend to create the first point in time of a future spider SRLI encompassing 200 species distributed across the world. A sample of 200 species of spiders were randomly selected from the World Spider Catalogue, an updated global database containing all recognised species names for the group. The 200 selected species where divided taxonomically at the family level and the familes were ordered alphabetically. In this publication, we present the conservation profiles of 46 species belonging to the famillies alphabetically arranged between Agelenidae and Filistatidae, which encompassed Agelenidae, Amaurobiidae, Anyphaenidae, Araneidae, Archaeidae, Barychelidae, Clubionidae, Corinnidae, Ctenidae, Ctenizidae, Cyatholipidae, Dictynidae, Dysderidae, Eresidae and Filistatidae.

Evaluating Concentrations of Heavy Metals in the U.S. Peanut Crop in the Presence of Detection Limits

USDA-ARS?s Scientific Manuscript database

The concentration of mercury, cadmium, lead, and arsenic along with glyphosate and an extensive array of pesticides in the U.S. peanut crop was assessed for crop years 2013-2015. Samples were randomly selected from various buying points during the grading process. Samples were selected from the thre...

Socio-Economic Background and Access to Internet as Correlates of Students' Achievement in Agricultural Science

ERIC Educational Resources Information Center

Adegoke, Sunday Paul; Osokoya, Modupe M.

2015-01-01

This study investigated access to internet and socio-economic background as correlates of students' achievement in Agricultural Science among selected Senior Secondary Schools Two Students in Ogbomoso South and North Local Government Areas. The study adopted multi-stage sampling technique. Simple random sampling was used to select 30 students from…

Quality of different in-clinic test systems for feline immunodeficiency virus and feline leukaemia virus infection.

PubMed

Hartmann, Katrin; Griessmayr, Pascale; Schulz, Bianka; Greene, Craig E; Vidyashankar, Anand N; Jarrett, Os; Egberink, Herman F

2007-12-01

Many new diagnostic in-house tests for identification of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) infection have been licensed for use in veterinary practice, and the question of the relative merits of these kits has prompted comparative studies. This study was designed to define the strengths and weaknesses of seven FIV and eight FeLV tests that are commercially available. In this study, 536 serum samples from randomly selected cats were tested. Those samples reacting FIV-positive in at least one of the tests were confirmed by Western blot, and those reacting FeLV-positive were confirmed by virus isolation. In addition, a random selection of samples testing negative in all test systems was re-tested by Western blot (100 samples) and by virus isolation (81 samples). Specificity, sensitivity, positive and negative predictive values of each test and the quality of the results were compared.

Sampling Strategies for Evaluating the Rate of Adventitious Transgene Presence in Non-Genetically Modified Crop Fields.

PubMed

Makowski, David; Bancal, Rémi; Bensadoun, Arnaud; Monod, Hervé; Messéan, Antoine

2017-09-01

According to E.U. regulations, the maximum allowable rate of adventitious transgene presence in non-genetically modified (GM) crops is 0.9%. We compared four sampling methods for the detection of transgenic material in agricultural non-GM maize fields: random sampling, stratified sampling, random sampling + ratio reweighting, random sampling + regression reweighting. Random sampling involves simply sampling maize grains from different locations selected at random from the field concerned. The stratified and reweighting sampling methods make use of an auxiliary variable corresponding to the output of a gene-flow model (a zero-inflated Poisson model) simulating cross-pollination as a function of wind speed, wind direction, and distance to the closest GM maize field. With the stratified sampling method, an auxiliary variable is used to define several strata with contrasting transgene presence rates, and grains are then sampled at random from each stratum. With the two methods involving reweighting, grains are first sampled at random from various locations within the field, and the observations are then reweighted according to the auxiliary variable. Data collected from three maize fields were used to compare the four sampling methods, and the results were used to determine the extent to which transgene presence rate estimation was improved by the use of stratified and reweighting sampling methods. We found that transgene rate estimates were more accurate and that substantially smaller samples could be used with sampling strategies based on an auxiliary variable derived from a gene-flow model. © 2017 Society for Risk Analysis.

The coalescent process in models with selection and recombination.

PubMed

Hudson, R R; Kaplan, N L

1988-11-01

The statistical properties of the process describing the genealogical history of a random sample of genes at a selectively neutral locus which is linked to a locus at which natural selection operates are investigated. It is found that the equations describing this process are simple modifications of the equations describing the process assuming that the two loci are completely linked. Thus, the statistical properties of the genealogical process for a random sample at a neutral locus linked to a locus with selection follow from the results obtained for the selected locus. Sequence data from the alcohol dehydrogenase (Adh) region of Drosophila melanogaster are examined and compared to predictions based on the theory. It is found that the spatial distribution of nucleotide differences between Fast and Slow alleles of Adh is very similar to the spatial distribution predicted if balancing selection operates to maintain the allozyme variation at the Adh locus. The spatial distribution of nucleotide differences between different Slow alleles of Adh do not match the predictions of this simple model very well.

Classification of epileptic EEG signals based on simple random sampling and sequential feature selection.

PubMed

Ghayab, Hadi Ratham Al; Li, Yan; Abdulla, Shahab; Diykh, Mohammed; Wan, Xiangkui

2016-06-01

Electroencephalogram (EEG) signals are used broadly in the medical fields. The main applications of EEG signals are the diagnosis and treatment of diseases such as epilepsy, Alzheimer, sleep problems and so on. This paper presents a new method which extracts and selects features from multi-channel EEG signals. This research focuses on three main points. Firstly, simple random sampling (SRS) technique is used to extract features from the time domain of EEG signals. Secondly, the sequential feature selection (SFS) algorithm is applied to select the key features and to reduce the dimensionality of the data. Finally, the selected features are forwarded to a least square support vector machine (LS_SVM) classifier to classify the EEG signals. The LS_SVM classifier classified the features which are extracted and selected from the SRS and the SFS. The experimental results show that the method achieves 99.90, 99.80 and 100 % for classification accuracy, sensitivity and specificity, respectively.

Sampling large random knots in a confined space

NASA Astrophysics Data System (ADS)

Arsuaga, J.; Blackstone, T.; Diao, Y.; Hinson, K.; Karadayi, E.; Saito, M.

2007-09-01

DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e^{n^2}) . We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n2). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications.

Using a Calendar and Explanatory Instructions to Aid Within-Household Selection in Mail Surveys

ERIC Educational Resources Information Center

Stange, Mathew; Smyth, Jolene D.; Olson, Kristen

2016-01-01

Although researchers can easily select probability samples of addresses using the U.S. Postal Service's Delivery Sequence File, randomly selecting respondents within households for surveys remains challenging. Researchers often place within-household selection instructions, such as the next or last birthday methods, in survey cover letters to…

Study of The Vector Product using Three Dimensions Vector Card of Engineering in Pathumwan Institute of Technology

NASA Astrophysics Data System (ADS)

Mueanploy, Wannapa

2015-06-01

The objective of this research was to offer the way to improve engineering students in Physics topic of vector product. The sampling of this research was the engineering students at Pathumwan Institute of Technology during the first semester of academic year 2013. 1) Select 120 students by random sampling are asked to fill in a satisfaction questionnaire scale, to select size of three dimensions vector card in order to apply in the classroom. 2) Select 60 students by random sampling to do achievement test and take the test to be used in the classroom. The methods used in analysis of achievement test by the Kuder-Richardson Method (KR- 20). The results show that 12 items of achievement test are appropriate to be applied in the classroom. The achievement test gets Difficulty (P) = 0.40-0.67, Discrimination = 0.33-0.73 and Reliability (r) = 0.70.The experimental in the classroom. 3) Select 60 students by random sampling divide into two groups; group one (the controlled group) with 30 students was chosen to study in the vector product lesson by the regular teaching method. Group two (the experimental group) with 30 students was chosen to learn the vector product lesson with three dimensions vector card. 4) Analyzed data between the controlled group and the experimental group, the result showed that experimental group got higher achievement test than the controlled group significant at .01 level.

A sampling design framework for monitoring secretive marshbirds

USGS Publications Warehouse

Johnson, D.H.; Gibbs, J.P.; Herzog, M.; Lor, S.; Niemuth, N.D.; Ribic, C.A.; Seamans, M.; Shaffer, T.L.; Shriver, W.G.; Stehman, S.V.; Thompson, W.L.

2009-01-01

A framework for a sampling plan for monitoring marshbird populations in the contiguous 48 states is proposed here. The sampling universe is the breeding habitat (i.e. wetlands) potentially used by marshbirds. Selection protocols would be implemented within each of large geographical strata, such as Bird Conservation Regions. Site selection will be done using a two-stage cluster sample. Primary sampling units (PSUs) would be land areas, such as legal townships, and would be selected by a procedure such as systematic sampling. Secondary sampling units (SSUs) will be wetlands or portions of wetlands in the PSUs. SSUs will be selected by a randomized spatially balanced procedure. For analysis, the use of a variety of methods as a means of increasing confidence in conclusions that may be reached is encouraged. Additional effort will be required to work out details and implement the plan.

An evaluation of flow-stratified sampling for estimating suspended sediment loads

Treesearch

Robert B. Thomas; Jack Lewis

1995-01-01

Abstract - Flow-stratified sampling is a new method for sampling water quality constituents such as suspended sediment to estimate loads. As with selection-at-list-time (SALT) and time-stratified sampling, flow-stratified sampling is a statistical method requiring random sampling, and yielding unbiased estimates of load and variance. It can be used to estimate event...

How Much Videos Win over Audios in Listening Instruction for EFL Learners

ERIC Educational Resources Information Center

Yasin, Burhanuddin; Mustafa, Faisal; Permatasari, Rizki

2017-01-01

This study aims at comparing the benefits of using videos instead of audios for improving students' listening skills. This experimental study used a pre-test and post-test control group design. The sample, selected by cluster random sampling resulted in the selection of 32 second year high school students for each group. The instruments used were…

Correcting Classifiers for Sample Selection Bias in Two-Phase Case-Control Studies

PubMed Central

Theis, Fabian J.

2017-01-01

Epidemiological studies often utilize stratified data in which rare outcomes or exposures are artificially enriched. This design can increase precision in association tests but distorts predictions when applying classifiers on nonstratified data. Several methods correct for this so-called sample selection bias, but their performance remains unclear especially for machine learning classifiers. With an emphasis on two-phase case-control studies, we aim to assess which corrections to perform in which setting and to obtain methods suitable for machine learning techniques, especially the random forest. We propose two new resampling-based methods to resemble the original data and covariance structure: stochastic inverse-probability oversampling and parametric inverse-probability bagging. We compare all techniques for the random forest and other classifiers, both theoretically and on simulated and real data. Empirical results show that the random forest profits from only the parametric inverse-probability bagging proposed by us. For other classifiers, correction is mostly advantageous, and methods perform uniformly. We discuss consequences of inappropriate distribution assumptions and reason for different behaviors between the random forest and other classifiers. In conclusion, we provide guidance for choosing correction methods when training classifiers on biased samples. For random forests, our method outperforms state-of-the-art procedures if distribution assumptions are roughly fulfilled. We provide our implementation in the R package sambia. PMID:29312464

GIS-based support vector machine modeling of earthquake-triggered landslide susceptibility in the Jianjiang River watershed, China

NASA Astrophysics Data System (ADS)

Xu, Chong; Dai, Fuchu; Xu, Xiwei; Lee, Yuan Hsi

2012-04-01

Support vector machine (SVM) modeling is based on statistical learning theory. It involves a training phase with associated input and target output values. In recent years, the method has become increasingly popular. The main purpose of this study is to evaluate the mapping power of SVM modeling in earthquake triggered landslide-susceptibility mapping for a section of the Jianjiang River watershed using a Geographic Information System (GIS) software. The river was affected by the Wenchuan earthquake of May 12, 2008. Visual interpretation of colored aerial photographs of 1-m resolution and extensive field surveys provided a detailed landslide inventory map containing 3147 landslides related to the 2008 Wenchuan earthquake. Elevation, slope angle, slope aspect, distance from seismogenic faults, distance from drainages, and lithology were used as the controlling parameters. For modeling, three groups of positive and negative training samples were used in concert with four different kernel functions. Positive training samples include the centroids of 500 large landslides, those of all 3147 landslides, and 5000 randomly selected points in landslide polygons. Negative training samples include 500, 3147, and 5000 randomly selected points on slopes that remained stable during the Wenchuan earthquake. The four kernel functions are linear, polynomial, radial basis, and sigmoid. In total, 12 cases of landslide susceptibility were mapped. Comparative analyses of landslide-susceptibility probability and area relation curves show that both the polynomial and radial basis functions suitably classified the input data as either landslide positive or negative though the radial basis function was more successful. The 12 generated landslide-susceptibility maps were compared with known landslide centroid locations and landslide polygons to verify the success rate and predictive accuracy of each model. The 12 results were further validated using area-under-curve analysis. Group 3 with 5000 randomly selected points on the landslide polygons, and 5000 randomly selected points along stable slopes gave the best results with a success rate of 79.20% and predictive accuracy of 79.13% under the radial basis function. Of all the results, the sigmoid kernel function was the least skillful when used in concert with the centroid data of all 3147 landslides as positive training samples, and the negative training samples of 3147 randomly selected points in regions of stable slope (success rate = 54.95%; predictive accuracy = 61.85%). This paper also provides suggestions and reference data for selecting appropriate training samples and kernel function types for earthquake triggered landslide-susceptibility mapping using SVM modeling. Predictive landslide-susceptibility maps could be useful in hazard mitigation by helping planners understand the probability of landslides in different regions.

Using ArcMap, Google Earth, and Global Positioning Systems to select and locate random households in rural Haiti.

PubMed

Wampler, Peter J; Rediske, Richard R; Molla, Azizur R

2013-01-18

A remote sensing technique was developed which combines a Geographic Information System (GIS); Google Earth, and Microsoft Excel to identify home locations for a random sample of households in rural Haiti. The method was used to select homes for ethnographic and water quality research in a region of rural Haiti located within 9 km of a local hospital and source of health education in Deschapelles, Haiti. The technique does not require access to governmental records or ground based surveys to collect household location data and can be performed in a rapid, cost-effective manner. The random selection of households and the location of these households during field surveys were accomplished using GIS, Google Earth, Microsoft Excel, and handheld Garmin GPSmap 76CSx GPS units. Homes were identified and mapped in Google Earth, exported to ArcMap 10.0, and a random list of homes was generated using Microsoft Excel which was then loaded onto handheld GPS units for field location. The development and use of a remote sensing method was essential to the selection and location of random households. A total of 537 homes initially were mapped and a randomized subset of 96 was identified as potential survey locations. Over 96% of the homes mapped using Google Earth imagery were correctly identified as occupied dwellings. Only 3.6% of the occupants of mapped homes visited declined to be interviewed. 16.4% of the homes visited were not occupied at the time of the visit due to work away from the home or market days. A total of 55 households were located using this method during the 10 days of fieldwork in May and June of 2012. The method used to generate and field locate random homes for surveys and water sampling was an effective means of selecting random households in a rural environment lacking geolocation infrastructure. The success rate for locating households using a handheld GPS was excellent and only rarely was local knowledge required to identify and locate households. This method provides an important technique that can be applied to other developing countries where a randomized study design is needed but infrastructure is lacking to implement more traditional participant selection methods.

THE SOCIAL PROBLEMS OF MIGRANT FARM LABORERS--EFFECT OF MIGRANT FARM LABOR ON THE EDUCATION OF CHILDREN.

ERIC Educational Resources Information Center

BROOKS, MELVIN S.; HILGENDORF, ROBERT L.

MIGRANT LABORERS WHO PICKED STRAWBERRIES IN SOUTHERN ILLINOIS IN THE SPRING OF 1958 WERE SURVEYED. THIS PARTICULAR SAMPLE WAS SELECTED FOR STUDY BECAUSE FAR MORE CHILDREN ARE INVOLVED IN THE HARVEST OF STRAWBERRIES THAN IN ANY OTHER FARM TASK OF THE AREA. MIGRANTS WHO WERE INTERVIEWED WERE SELECTED BY SYSTEMATIC RANDOM SAMPLING--A PROCEDURE THAT…

Mountain bike trail compaction relation to selected physical parameters

Treesearch

Jeff Hale; Rodney R. Zwick

2002-01-01

The purpose of this research is to explore the rates of compaction and their relation to trail contextual aspects of: soil type, slope and crown cover on a newly established mountain bike trail in the northern reach of Vermont. A random sample of 52 sites was selected for monitoring on the 1.09-mile trail. Three penetrometer readings were taken at each of the sample...

What Are Probability Surveys used by the National Aquatic Resource Surveys?

EPA Pesticide Factsheets

The National Aquatic Resource Surveys (NARS) use probability-survey designs to assess the condition of the nation’s waters. In probability surveys (also known as sample-surveys or statistical surveys), sampling sites are selected randomly.

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...

Piecewise SALT sampling for estimating suspended sediment yields

Treesearch

Robert B. Thomas

1989-01-01

A probability sampling method called SALT (Selection At List Time) has been developed for collecting and summarizing data on delivery of suspended sediment in rivers. It is based on sampling and estimating yield using a suspended-sediment rating curve for high discharges and simple random sampling for low flows. The method gives unbiased estimates of total yield and...

Statistical auditing and randomness test of lotto k/N-type games

NASA Astrophysics Data System (ADS)

Coronel-Brizio, H. F.; Hernández-Montoya, A. R.; Rapallo, F.; Scalas, E.

2008-11-01

One of the most popular lottery games worldwide is the so-called “lotto k/N”. It considers N numbers 1,2,…,N from which k are drawn randomly, without replacement. A player selects k or more numbers and the first prize is shared amongst those players whose selected numbers match all of the k randomly drawn. Exact rules may vary in different countries. In this paper, mean values and covariances for the random variables representing the numbers drawn from this kind of game are presented, with the aim of using them to audit statistically the consistency of a given sample of historical results with theoretical values coming from a hypergeometric statistical model. The method can be adapted to test pseudorandom number generators.

A comparison of two sampling designs for fish assemblage assessment in a large river

USGS Publications Warehouse

Kiraly, Ian A.; Coghlan, Stephen M.; Zydlewski, Joseph D.; Hayes, Daniel

2014-01-01

We compared the efficiency of stratified random and fixed-station sampling designs to characterize fish assemblages in anticipation of dam removal on the Penobscot River, the largest river in Maine. We used boat electrofishing methods in both sampling designs. Multiple 500-m transects were selected randomly and electrofished in each of nine strata within the stratified random sampling design. Within the fixed-station design, up to 11 transects (1,000 m) were electrofished, all of which had been sampled previously. In total, 88 km of shoreline were electrofished during summer and fall in 2010 and 2011, and 45,874 individuals of 34 fish species were captured. Species-accumulation and dissimilarity curve analyses indicated that all sampling effort, other than fall 2011 under the fixed-station design, provided repeatable estimates of total species richness and proportional abundances. Overall, our sampling designs were similar in precision and efficiency for sampling fish assemblages. The fixed-station design was negatively biased for estimating the abundance of species such as Common Shiner Luxilus cornutus and Fallfish Semotilus corporalis and was positively biased for estimating biomass for species such as White Sucker Catostomus commersonii and Atlantic Salmon Salmo salar. However, we found no significant differences between the designs for proportional catch and biomass per unit effort, except in fall 2011. The difference observed in fall 2011 was due to limitations on the number and location of fixed sites that could be sampled, rather than an inherent bias within the design. Given the results from sampling in the Penobscot River, application of the stratified random design is preferable to the fixed-station design due to less potential for bias caused by varying sampling effort, such as what occurred in the fall 2011 fixed-station sample or due to purposeful site selection.

Errors in causal inference: an organizational schema for systematic error and random error.

PubMed

Suzuki, Etsuji; Tsuda, Toshihide; Mitsuhashi, Toshiharu; Mansournia, Mohammad Ali; Yamamoto, Eiji

2016-11-01

To provide an organizational schema for systematic error and random error in estimating causal measures, aimed at clarifying the concept of errors from the perspective of causal inference. We propose to divide systematic error into structural error and analytic error. With regard to random error, our schema shows its four major sources: nondeterministic counterfactuals, sampling variability, a mechanism that generates exposure events and measurement variability. Structural error is defined from the perspective of counterfactual reasoning and divided into nonexchangeability bias (which comprises confounding bias and selection bias) and measurement bias. Directed acyclic graphs are useful to illustrate this kind of error. Nonexchangeability bias implies a lack of "exchangeability" between the selected exposed and unexposed groups. A lack of exchangeability is not a primary concern of measurement bias, justifying its separation from confounding bias and selection bias. Many forms of analytic errors result from the small-sample properties of the estimator used and vanish asymptotically. Analytic error also results from wrong (misspecified) statistical models and inappropriate statistical methods. Our organizational schema is helpful for understanding the relationship between systematic error and random error from a previously less investigated aspect, enabling us to better understand the relationship between accuracy, validity, and precision. Copyright © 2016 Elsevier Inc. All rights reserved.

Randomization of grab-sampling strategies for estimating the annual exposure of U miners to Rn daughters.

PubMed

Borak, T B

1986-04-01

Periodic grab sampling in combination with time-of-occupancy surveys has been the accepted procedure for estimating the annual exposure of underground U miners to Rn daughters. Temporal variations in the concentration of potential alpha energy in the mine generate uncertainties in this process. A system to randomize the selection of locations for measurement is described which can reduce uncertainties and eliminate systematic biases in the data. In general, a sample frequency of 50 measurements per year is sufficient to satisfy the criteria that the annual exposure be determined in working level months to within +/- 50% of the true value with a 95% level of confidence. Suggestions for implementing this randomization scheme are presented.

DEVELOPMENT OF MACROINVERTEBRATE INDICATORS FOR NONWADEABLE TRIBUTARIES TO THE OHIO AND MISSISSIPPI RIVERS

EPA Science Inventory

In 2004-02005, macroinvertebrates were sampled from selected large rivers of the upper Midwest to develop appropriate assessment indicators. Macroinvertebrates, habitat and water chemistry data were collected from 132 randomly selected sites across 6 rivers with varying land cove...

Quantifying Uncertainties from Presence Data Sampling Methods for Species Distribution Modeling: Focused on Vegetation.

NASA Astrophysics Data System (ADS)

Sung, S.; Kim, H. G.; Lee, D. K.; Park, J. H.; Mo, Y.; Kil, S.; Park, C.

2016-12-01

The impact of climate change has been observed throughout the globe. The ecosystem experiences rapid changes such as vegetation shift, species extinction. In these context, Species Distribution Model (SDM) is one of the popular method to project impact of climate change on the ecosystem. SDM basically based on the niche of certain species with means to run SDM present point data is essential to find biological niche of species. To run SDM for plants, there are certain considerations on the characteristics of vegetation. Normally, to make vegetation data in large area, remote sensing techniques are used. In other words, the exact point of presence data has high uncertainties as we select presence data set from polygons and raster dataset. Thus, sampling methods for modeling vegetation presence data should be carefully selected. In this study, we used three different sampling methods for selection of presence data of vegetation: Random sampling, Stratified sampling and Site index based sampling. We used one of the R package BIOMOD2 to access uncertainty from modeling. At the same time, we included BioCLIM variables and other environmental variables as input data. As a result of this study, despite of differences among the 10 SDMs, the sampling methods showed differences in ROC values, random sampling methods showed the lowest ROC value while site index based sampling methods showed the highest ROC value. As a result of this study the uncertainties from presence data sampling methods and SDM can be quantified.

Selective Exposure and Retention of Political Advertising: A Regional Comparison.

ERIC Educational Resources Information Center

Surlin, Stuart H.; Gordon, Thomas F.

The results presented in this article are but a portion of the information gathered in a larger survey examining the relative roles of "selective exposure" to and "selective retention" of political advertising during the 1972 presidential election. Random samples in two metropolitan areas in different regions of the country (Atlanta, Ga., n=281;…

Selected Health Practices Among Ohio's Rural Residents.

ERIC Educational Resources Information Center

Phillips, G. Howard; Pugh, Albert

Using a stratified random sample of 12 of Ohio's 88 counties, this 1967 study had as its objectives (1) to measure the level of participation in selected health practices by Ohio's rural residents, (2) to compare the level of participation in selected health practices of farm and rural nonfarm residents, and (3) to examine levels of participation…

Estimating Sampling Selection Bias in Human Genetics: A Phenomenological Approach

PubMed Central

Risso, Davide; Taglioli, Luca; De Iasio, Sergio; Gueresi, Paola; Alfani, Guido; Nelli, Sergio; Rossi, Paolo; Paoli, Giorgio; Tofanelli, Sergio

2015-01-01

This research is the first empirical attempt to calculate the various components of the hidden bias associated with the sampling strategies routinely-used in human genetics, with special reference to surname-based strategies. We reconstructed surname distributions of 26 Italian communities with different demographic features across the last six centuries (years 1447–2001). The degree of overlapping between "reference founding core" distributions and the distributions obtained from sampling the present day communities by probabilistic and selective methods was quantified under different conditions and models. When taking into account only one individual per surname (low kinship model), the average discrepancy was 59.5%, with a peak of 84% by random sampling. When multiple individuals per surname were considered (high kinship model), the discrepancy decreased by 8–30% at the cost of a larger variance. Criteria aimed at maximizing locally-spread patrilineages and long-term residency appeared to be affected by recent gene flows much more than expected. Selection of the more frequent family names following low kinship criteria proved to be a suitable approach only for historically stable communities. In any other case true random sampling, despite its high variance, did not return more biased estimates than other selective methods. Our results indicate that the sampling of individuals bearing historically documented surnames (founders' method) should be applied, especially when studying the male-specific genome, to prevent an over-stratification of ancient and recent genetic components that heavily biases inferences and statistics. PMID:26452043

Estimating Sampling Selection Bias in Human Genetics: A Phenomenological Approach.

PubMed

Risso, Davide; Taglioli, Luca; De Iasio, Sergio; Gueresi, Paola; Alfani, Guido; Nelli, Sergio; Rossi, Paolo; Paoli, Giorgio; Tofanelli, Sergio

2015-01-01

This research is the first empirical attempt to calculate the various components of the hidden bias associated with the sampling strategies routinely-used in human genetics, with special reference to surname-based strategies. We reconstructed surname distributions of 26 Italian communities with different demographic features across the last six centuries (years 1447-2001). The degree of overlapping between "reference founding core" distributions and the distributions obtained from sampling the present day communities by probabilistic and selective methods was quantified under different conditions and models. When taking into account only one individual per surname (low kinship model), the average discrepancy was 59.5%, with a peak of 84% by random sampling. When multiple individuals per surname were considered (high kinship model), the discrepancy decreased by 8-30% at the cost of a larger variance. Criteria aimed at maximizing locally-spread patrilineages and long-term residency appeared to be affected by recent gene flows much more than expected. Selection of the more frequent family names following low kinship criteria proved to be a suitable approach only for historically stable communities. In any other case true random sampling, despite its high variance, did not return more biased estimates than other selective methods. Our results indicate that the sampling of individuals bearing historically documented surnames (founders' method) should be applied, especially when studying the male-specific genome, to prevent an over-stratification of ancient and recent genetic components that heavily biases inferences and statistics.

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…

Evaluation of Students' Perceptions about Efficiency of Educational Club Practices in Primary Schools

ERIC Educational Resources Information Center

Gelen, Ismail; Onay, Ihsan; Varol, Volkan

2014-01-01

The purpose of this study is to examine the efficiency of "Educational Club Practices" that has been in Elementary School program since 2005-2006, by examining the attitudes of students about "Educational Club Practices". Sample was selected in two steps. First, stratified sampling was employed and then random sampling was…

Adiposity and Quality of Life: A Case Study from an Urban Center in Nigeria

ERIC Educational Resources Information Center

Akinpelu, Aderonke O.; Akinola, Odunayo T.; Gbiri, Caleb A.

2009-01-01

Objective: To determine relationship between adiposity indices and quality of life (QOL) of residents of a housing estate in Lagos, Nigeria. Design: Cross-sectional survey employing multistep random sampling method. Setting: Urban residential estate. Participants: This study involved 900 randomly selected residents of Abesan Housing Estate, Lagos,…

The Role of Religiosity in Influencing Adolescent and Adult Alcohol Use in Trinidad

ERIC Educational Resources Information Center

Rollocks, Steve C. T.; Dass, Natasha; Seepersad, Randy; Mohammed, Linda

2008-01-01

This study examined the role of religiosity among adolescents' and adults' alcohol use in Trinidad. A stratified random sample design of 369 adolescents and 210 adult parents belonging to the various religious groups in Trinidad was employed. Participants were randomly selected from various educational districts across Trinidad. Adolescent…

Feature Selection for Ridge Regression with Provable Guarantees.

PubMed

Paul, Saurabh; Drineas, Petros

2016-04-01

We introduce single-set spectral sparsification as a deterministic sampling-based feature selection technique for regularized least-squares classification, which is the classification analog to ridge regression. The method is unsupervised and gives worst-case guarantees of the generalization power of the classification function after feature selection with respect to the classification function obtained using all features. We also introduce leverage-score sampling as an unsupervised randomized feature selection method for ridge regression. We provide risk bounds for both single-set spectral sparsification and leverage-score sampling on ridge regression in the fixed design setting and show that the risk in the sampled space is comparable to the risk in the full-feature space. We perform experiments on synthetic and real-world data sets; a subset of TechTC-300 data sets, to support our theory. Experimental results indicate that the proposed methods perform better than the existing feature selection methods.

The Accuracy of Estimated Total Test Statistics. Final Report.

ERIC Educational Resources Information Center

Kleinke, David J.

In a post-mortem study of item sampling, 1,050 examinees were divided into ten groups 50 times. Each time, their papers were scored on four different sets of item samples from a 150-item test of academic aptitude. These samples were selected using (a) unstratified random sampling and stratification on (b) content, (c) difficulty, and (d) both.…

Fitting distributions to microbial contamination data collected with an unequal probability sampling design.

PubMed

Williams, M S; Ebel, E D; Cao, Y

2013-01-01

The fitting of statistical distributions to microbial sampling data is a common application in quantitative microbiology and risk assessment applications. An underlying assumption of most fitting techniques is that data are collected with simple random sampling, which is often times not the case. This study develops a weighted maximum likelihood estimation framework that is appropriate for microbiological samples that are collected with unequal probabilities of selection. A weighted maximum likelihood estimation framework is proposed for microbiological samples that are collected with unequal probabilities of selection. Two examples, based on the collection of food samples during processing, are provided to demonstrate the method and highlight the magnitude of biases in the maximum likelihood estimator when data are inappropriately treated as a simple random sample. Failure to properly weight samples to account for how data are collected can introduce substantial biases into inferences drawn from the data. The proposed methodology will reduce or eliminate an important source of bias in inferences drawn from the analysis of microbial data. This will also make comparisons between studies and the combination of results from different studies more reliable, which is important for risk assessment applications. © 2012 No claim to US Government works.

Microbial contamination of meat during the skinning of beef carcass hindquarters at three slaughtering plants.

PubMed

Gill, C O; McGinnis, J C; Bryant, J

1998-07-21

The microbiological effects on the product of the series of operations for skinning the hindquarters of beef carcasses at three packing plants were assessed. Samples were obtained at each plant from randomly selected carcasses, by swabbing specified sites related to opening cuts, rump skinning or flank skinning operations, randomly selected sites along the lines of the opening cuts, or randomly selected sites on the skinned hindquarters of carcasses. A set of 25 samples of each type was collected at each plant, with the collection of a single sample from each selected carcass. Aerobic counts, coliforms and Escherichia coli were enumerated in each sample, and a log mean value was estimated for each set of 25 counts on the assumption of a log normal distribution of the counts. The data indicated that the hindquarters skinning operations at plant A were hygienically inferior to those at the other two plants, with mean numbers of coliforms and E. coli being about two orders of magnitude greater, and aerobic counts being an order of magnitude greater on the skinned hindquarters of carcasses from plant A than on those from plants B or C. The data further indicated that the operation for cutting open the skin at plant C was hygienically superior to the equivalent operation at plant B, but that the operations for skinning the rump and flank at plant B were hygienically superior to the equivalent operations at plant C. The findings suggest that objective assessment of the microbiological effects on carcasses of beef carcass dressing processes will be required to ensure that Hazard Analysis: Critical Control Point and Quality Management Systems are operated to control the microbiological condition of carcasses.

Antibiotic resistance profiles of coagulase-positive and coagulase-negative staphylococci from pit latrine fecal sludge in a peri-urban South African community.

PubMed

Beukes, Lorika S; Schmidt, Stefan

2018-04-16

The aim of this study was to assess pit latrine samples from a peri-urban community in KwaZulu-Natal (South Africa) for the presence of multidrug-resistant (MDR) Staphylococcus spp. Standard procedures were used to isolate Staphylococcus spp. from pit latrine fecal sludge samples, with confirmation at genus level by polymerase chain reaction (PCR). Sixty-eight randomly selected pit latrine Staphylococcus spp. isolates were further characterized by using established disk diffusion procedures. An average Staphylococcus spp. count of 2.1 × 10 5  CFU per g fecal material was established using two randomly selected pit latrine samples. Of the 68-selected Staphylococcus spp. pit latrine isolates, 49% were identified as coagulase positive, 51% as coagulase negative and 65% (12 coagulase positive, 32 coagulase negative isolates) were categorized as MDR. The majority (66/68) of Staphylococcus spp. isolates displayed resistance to fusidic acid while only 5/68 isolates displayed resistance to chloramphenicol. The pit latrine samples analyzed in this study are a source of MDR Staphylococcus spp., highlighting the need for proper hygiene and sanitation regimes in rural communities using these facilities.

Prevalence of paratuberculosis in the dairy goat and dairy sheep industries in Ontario, Canada.

PubMed

Bauman, Cathy A; Jones-Bitton, Andria; Menzies, Paula; Toft, Nils; Jansen, Jocelyn; Kelton, David

2016-02-01

A cross-sectional study was undertaken (October 2010 to August 2011) to estimate the prevalence of paratuberculosis in the small ruminant dairy industries in Ontario, Canada. Blood and feces were sampled from 580 goats and 397 sheep (lactating and 2 y of age or older) that were randomly selected from 29 randomly selected dairy goat herds and 21 convenience-selected dairy sheep flocks. Fecal samples were analyzed using bacterial culture (BD BACTEC MGIT 960) and polymerase chain reaction (Tetracore); serum samples were tested with the Prionics Parachek enzyme-linked immunosorbent assay (ELISA). Using 3-test latent class Bayesian models, true farm-level prevalence was estimated to be 83.0% [95% probability interval (PI): 62.6% to 98.1%] for dairy goats and 66.8% (95% PI: 41.6% to 91.4%) for dairy sheep. The within-farm true prevalence for dairy goats was 35.2% (95% PI: 23.0% to 49.8%) and for dairy sheep was 48.3% (95% PI: 27.6% to 74.3%). These data indicate that a paratuberculosis control program for small ruminants is needed in Ontario.

Prevalence of Dental Fear and Anxiety amongst Patients in Selected Dental Clinics in Ghana

ERIC Educational Resources Information Center

Ofori, Marian A.; Adu-Ababio, F.; Nyako, E. A.; Ndanu, Tom A.

2009-01-01

Objective: To find out the prevalence of dental anxiety and fear amongst patients in various selected dental clinics in Accra, Ghana. Study design: Dental patients (n = 279) who had either been exposed to dental treatments or had no prior dental exposure, attending four selected dental clinics in Accra were randomly sampled. They were interviewed…

Prospective Evaluation of Intraprostatic Inflammation and Focal Atrophy as a Predictor of Risk of High-Grade Prostate Cancer and Recurrence after Prostatectomy

DTIC Science & Technology

2014-07-01

the two trials. The expected sample size for this work was 100 cases and 200 controls. Tissue was sufficient for 291 of the men (Task 2 completed in...not collected in SELECT), physical activity (PCPT [not collected in SELECT), cigarette smoking status at randomization (SELECT), use of aspirin

Students with Disabilities and Higher Education

ERIC Educational Resources Information Center

Singh, Delar K.

2005-01-01

This paper reports the findings of a national survey that collected data describing the selected facilities and services of 137 randomly selected institutions of higher learning. The survey was sent to the Directors of services for disabled students of the sample institutions. The findings indicate that only 7% of the institutions of higher…

Random phase detection in multidimensional NMR.

PubMed

Maciejewski, Mark W; Fenwick, Matthew; Schuyler, Adam D; Stern, Alan S; Gorbatyuk, Vitaliy; Hoch, Jeffrey C

2011-10-04

Despite advances in resolution accompanying the development of high-field superconducting magnets, biomolecular applications of NMR require multiple dimensions in order to resolve individual resonances, and the achievable resolution is typically limited by practical constraints on measuring time. In addition to the need for measuring long evolution times to obtain high resolution, the need to distinguish the sign of the frequency constrains the ability to shorten measuring times. Sign discrimination is typically accomplished by sampling the signal with two different receiver phases or by selecting a reference frequency outside the range of frequencies spanned by the signal and then sampling at a higher rate. In the parametrically sampled (indirect) time dimensions of multidimensional NMR experiments, either method imposes an additional factor of 2 sampling burden for each dimension. We demonstrate that by using a single detector phase at each time sample point, but randomly altering the phase for different points, the sign ambiguity that attends fixed single-phase detection is resolved. Random phase detection enables a reduction in experiment time by a factor of 2 for each indirect dimension, amounting to a factor of 8 for a four-dimensional experiment, albeit at the cost of introducing sampling artifacts. Alternatively, for fixed measuring time, random phase detection can be used to double resolution in each indirect dimension. Random phase detection is complementary to nonuniform sampling methods, and their combination offers the potential for additional benefits. In addition to applications in biomolecular NMR, random phase detection could be useful in magnetic resonance imaging and other signal processing contexts.

THE RELATIONSHIP BETWEEN TEMPERATURE, PHYSICAL HABITAT AND FISH ASSEMBLAGE DATA IN A STATE WIDE PROBABILITY SURVEY OF OREGON STREAMS

EPA Science Inventory

To assess the ecological condition of streams and rivers in Oregon, we sampled 146 sites
in summer, 1997 as part of the U.S. EPA's Environmental Monitoring and Assessment Program.
Sample reaches were selected using a systematic, randomized sample design from the blue-line n...

Burnout among Extension Agents in the Ohio Cooperative Extension Service.

ERIC Educational Resources Information Center

Igodan, O. Chris; Newcomb, L. H.

A study examined the extent and causes of burnout among extension agents in Ohio. From the 241 extension agents working in the 88 counties of Ohio, researchers selected a random sample of 101 agents. Included in the sample were 34 agriculture agents, 33 home economics agents. Included in the sample agents were asked to complete a survey…

An active learning representative subset selection method using net analyte signal.

PubMed

He, Zhonghai; Ma, Zhenhe; Luan, Jingmin; Cai, Xi

2018-05-05

To guarantee accurate predictions, representative samples are needed when building a calibration model for spectroscopic measurements. However, in general, it is not known whether a sample is representative prior to measuring its concentration, which is both time-consuming and expensive. In this paper, a method to determine whether a sample should be selected into a calibration set is presented. The selection is based on the difference of Euclidean norm of net analyte signal (NAS) vector between the candidate and existing samples. First, the concentrations and spectra of a group of samples are used to compute the projection matrix, NAS vector, and scalar values. Next, the NAS vectors of candidate samples are computed by multiplying projection matrix with spectra of samples. Scalar value of NAS is obtained by norm computation. The distance between the candidate set and the selected set is computed, and samples with the largest distance are added to selected set sequentially. Last, the concentration of the analyte is measured such that the sample can be used as a calibration sample. Using a validation test, it is shown that the presented method is more efficient than random selection. As a result, the amount of time and money spent on reference measurements is greatly reduced. Copyright © 2018 Elsevier B.V. All rights reserved.

An active learning representative subset selection method using net analyte signal

NASA Astrophysics Data System (ADS)

He, Zhonghai; Ma, Zhenhe; Luan, Jingmin; Cai, Xi

2018-05-01

To guarantee accurate predictions, representative samples are needed when building a calibration model for spectroscopic measurements. However, in general, it is not known whether a sample is representative prior to measuring its concentration, which is both time-consuming and expensive. In this paper, a method to determine whether a sample should be selected into a calibration set is presented. The selection is based on the difference of Euclidean norm of net analyte signal (NAS) vector between the candidate and existing samples. First, the concentrations and spectra of a group of samples are used to compute the projection matrix, NAS vector, and scalar values. Next, the NAS vectors of candidate samples are computed by multiplying projection matrix with spectra of samples. Scalar value of NAS is obtained by norm computation. The distance between the candidate set and the selected set is computed, and samples with the largest distance are added to selected set sequentially. Last, the concentration of the analyte is measured such that the sample can be used as a calibration sample. Using a validation test, it is shown that the presented method is more efficient than random selection. As a result, the amount of time and money spent on reference measurements is greatly reduced.

A model-based 'varimax' sampling strategy for a heterogeneous population.

PubMed

Akram, Nuzhat A; Farooqi, Shakeel R

2014-01-01

Sampling strategies are planned to enhance the homogeneity of a sample, hence to minimize confounding errors. A sampling strategy was developed to minimize the variation within population groups. Karachi, the largest urban agglomeration in Pakistan, was used as a model population. Blood groups ABO and Rh factor were determined for 3000 unrelated individuals selected through simple random sampling. Among them five population groups, namely Balochi, Muhajir, Pathan, Punjabi and Sindhi, based on paternal ethnicity were identified. An index was designed to measure the proportion of admixture at parental and grandparental levels. Population models based on index score were proposed. For validation, 175 individuals selected through stratified random sampling were genotyped for the three STR loci CSF1PO, TPOX and TH01. ANOVA showed significant differences across the population groups for blood groups and STR loci distribution. Gene diversity was higher across the sub-population model than in the agglomerated population. At parental level gene diversities are significantly higher across No admixture models than Admixture models. At grandparental level the difference was not significant. A sub-population model with no admixture at parental level was justified for sampling the heterogeneous population of Karachi.

Electrofishing Effort Required to Estimate Biotic Condition in Southern Idaho Rivers

EPA Science Inventory

An important issue surrounding biomonitoring in large rivers is the minimum sampling effort required to collect an adequate number of fish for accurate and precise determinations of biotic condition. During the summer of 2002, we sampled 15 randomly selected large-river sites in...

Economic Intervention and Parenting: A Randomized Experiment of Statewide Child Development Accounts

ERIC Educational Resources Information Center

Nam, Yunju; Wikoff, Nora; Sherraden, Michael

2016-01-01

Objective: We examine the effects of Child Development Accounts (CDAs) on parenting stress and practices. Methods: We use data from the SEED for Oklahoma Kids (SEED OK) experiment. SEED OK selected caregivers of infants from Oklahoma birth certificates using a probability sampling method, randomly assigned caregivers to the treatment (n = 1,132)…

Reform-Based-Instructional Method and Learning Styles on Students' Achievement and Retention in Mathematics: Administrative Implications

ERIC Educational Resources Information Center

Modebelu, M. N.; Ogbonna, C. C.

2014-01-01

This study aimed at determining the effect of reform-based-instructional method learning styles on students' achievement and retention in mathematics. A sample size of 119 students was randomly selected. The quasiexperimental design comprising pre-test, post-test, and randomized control group were employed. The Collin Rose learning styles…

Modeling the Stress Complexities of Teaching and Learning of School Physics in Nigeria

ERIC Educational Resources Information Center

Emetere, Moses E.

2014-01-01

This study was designed to investigate the validity of the stress complexity model (SCM) to teaching and learning of school physics in Abuja municipal area council of Abuja, North. About two hundred students were randomly selected by a simple random sampling technique from some schools within the Abuja municipal area council. A survey research…

CURE-SMOTE algorithm and hybrid algorithm for feature selection and parameter optimization based on random forests.

PubMed

Ma, Li; Fan, Suohai

2017-03-14

The random forests algorithm is a type of classifier with prominent universality, a wide application range, and robustness for avoiding overfitting. But there are still some drawbacks to random forests. Therefore, to improve the performance of random forests, this paper seeks to improve imbalanced data processing, feature selection and parameter optimization. We propose the CURE-SMOTE algorithm for the imbalanced data classification problem. Experiments on imbalanced UCI data reveal that the combination of Clustering Using Representatives (CURE) enhances the original synthetic minority oversampling technique (SMOTE) algorithms effectively compared with the classification results on the original data using random sampling, Borderline-SMOTE1, safe-level SMOTE, C-SMOTE, and k-means-SMOTE. Additionally, the hybrid RF (random forests) algorithm has been proposed for feature selection and parameter optimization, which uses the minimum out of bag (OOB) data error as its objective function. Simulation results on binary and higher-dimensional data indicate that the proposed hybrid RF algorithms, hybrid genetic-random forests algorithm, hybrid particle swarm-random forests algorithm and hybrid fish swarm-random forests algorithm can achieve the minimum OOB error and show the best generalization ability. The training set produced from the proposed CURE-SMOTE algorithm is closer to the original data distribution because it contains minimal noise. Thus, better classification results are produced from this feasible and effective algorithm. Moreover, the hybrid algorithm's F-value, G-mean, AUC and OOB scores demonstrate that they surpass the performance of the original RF algorithm. Hence, this hybrid algorithm provides a new way to perform feature selection and parameter optimization.

Observational studies of patients in the emergency department: a comparison of 4 sampling methods.

PubMed

Valley, Morgan A; Heard, Kennon J; Ginde, Adit A; Lezotte, Dennis C; Lowenstein, Steven R

2012-08-01

We evaluate the ability of 4 sampling methods to generate representative samples of the emergency department (ED) population. We analyzed the electronic records of 21,662 consecutive patient visits at an urban, academic ED. From this population, we simulated different models of study recruitment in the ED by using 2 sample sizes (n=200 and n=400) and 4 sampling methods: true random, random 4-hour time blocks by exact sample size, random 4-hour time blocks by a predetermined number of blocks, and convenience or "business hours." For each method and sample size, we obtained 1,000 samples from the population. Using χ(2) tests, we measured the number of statistically significant differences between the sample and the population for 8 variables (age, sex, race/ethnicity, language, triage acuity, arrival mode, disposition, and payer source). Then, for each variable, method, and sample size, we compared the proportion of the 1,000 samples that differed from the overall ED population to the expected proportion (5%). Only the true random samples represented the population with respect to sex, race/ethnicity, triage acuity, mode of arrival, language, and payer source in at least 95% of the samples. Patient samples obtained using random 4-hour time blocks and business hours sampling systematically differed from the overall ED patient population for several important demographic and clinical variables. However, the magnitude of these differences was not large. Common sampling strategies selected for ED-based studies may affect parameter estimates for several representative population variables. However, the potential for bias for these variables appears small. Copyright © 2012. Published by Mosby, Inc.

Catholic High Schools and Their Finances. 1986.

ERIC Educational Resources Information Center

Augenstein, John J.

This report is based on a randomly selected and stratified sample of 208 United States Catholic high schools. The sample was stratified by governance (diocesan, parochial/interparochial, and private); five categories of enrollment; and six regions. Data are compared with an earlier study, "The Catholic High School: A National Portrait" and show…

Employee Engagement and Performance of Lecturers in Nigerian Tertiary Institutions

ERIC Educational Resources Information Center

Agbionu, Uchenna Clementina; Anyalor, Maureen; Nwali, Anthony Chukwuma

2018-01-01

The study investigated employee engagement and performance of lecturers in Nigerian Tertiary Institutions. It employed descriptive and correlation research designs. Stratified random sampling was used to select three tertiary institutions in Nigeria and the sample size of 314 lecturers was obtained through Taro Yamane. Questionnaires were…

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…

A Comparative Study of Students' Access to and Utilization of Learning Resources in Selected Public and Private Universities in Southwest, Nigeria

ERIC Educational Resources Information Center

Lawal, B. O.; Viatonu, Olumuyiwa

2017-01-01

The study investigated students' access to and utilization of some learning resources in selected public and private universities in southwest Nigeria. Stratified random sampling technique was used to select 585 (295 public and 290 private) students from 12 (six public and six private) universities in southwest Nigeria. Two instruments--Cost and…

Latin Hypercube Sampling (LHS) UNIX Library/Standalone

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

2004-05-13

The LHS UNIX Library/Standalone software provides the capability to draw random samples from over 30 distribution types. It performs the sampling by a stratified sampling method called Latin Hypercube Sampling (LHS). Multiple distributions can be sampled simultaneously, with user-specified correlations amongst the input distributions, LHS UNIX Library/ Standalone provides a way to generate multi-variate samples. The LHS samples can be generated either as a callable library (e.g., from within the DAKOTA software framework) or as a standalone capability. LHS UNIX Library/Standalone uses the Latin Hypercube Sampling method (LHS) to generate samples. LHS is a constrained Monte Carlo sampling scheme. Inmore » LHS, the range of each variable is divided into non-overlapping intervals on the basis of equal probability. A sample is selected at random with respect to the probability density in each interval, If multiple variables are sampled simultaneously, then values obtained for each are paired in a random manner with the n values of the other variables. In some cases, the pairing is restricted to obtain specified correlations amongst the input variables. Many simulation codes have input parameters that are uncertain and can be specified by a distribution, To perform uncertainty analysis and sensitivity analysis, random values are drawn from the input parameter distributions, and the simulation is run with these values to obtain output values. If this is done repeatedly, with many input samples drawn, one can build up a distribution of the output as well as examine correlations between input and output variables.« less

Evaluation of bias and logistics in a survey of adults at increased risk for oral health decrements.

PubMed

Gilbert, G H; Duncan, R P; Kulley, A M; Coward, R T; Heft, M W

1997-01-01

Designing research to include sufficient respondents in groups at highest risk for oral health decrements can present unique challenges. Our purpose was to evaluate bias and logistics in this survey of adults at increased risk for oral health decrements. We used a telephone survey methodology that employed both listed numbers and random digit dialing to identify dentate persons 45 years old or older and to oversample blacks, poor persons, and residents of nonmetropolitan counties. At a second stage, a subsample of the respondents to the initial telephone screening was selected for further study, which consisted of a baseline in-person interview and a clinical examination. We assessed bias due to: (1) limiting the sample to households with telephones, (2) using predominantly listed numbers instead of random digit dialing, and (3) nonresponse at two stages of data collection. While this approach apparently created some biases in the sample, they were small in magnitude. Specifically, limiting the sample to households with telephones biased the sample overall toward more females, larger households, and fewer functionally impaired persons. Using predominantly listed numbers led to a modest bias toward selection of persons more likely to be younger, healthier, female, have had a recent dental visit, and reside in smaller households. Blacks who were selected randomly at a second stage were more likely to participate in baseline data gathering than their white counterparts. Comparisons of the data obtained in this survey with those from recent national surveys suggest that this methodology for sampling high-risk groups did not substantively bias the sample with respect to two important dental parameters, prevalence of edentulousness and dental care use, nor were conclusions about multivariate associations with dental care recency substantively affected. This method of sampling persons at high risk for oral health decrements resulted in only modest bias with respect to the population of interest.

Mathematics Skill of Fifteen Years Old Students in Yogyakarta in Solving Problems Like PISA

ERIC Educational Resources Information Center

Wulandari, Nidya Ferry; Jailani

2018-01-01

The aims of this research were to describe mathematics skill of 8th fifteen-year old students in Yogyakarta in solving problem of PISA. The sampling was combination of stratified and cluster random sampling. The sample consisting of 400 students was selected from fifteen schools. The data collection was by tests. The research finding revealed that…

Types of Bullying in the Senior High Schools in Ghana

ERIC Educational Resources Information Center

Antiri, Kwasi Otopa

2016-01-01

The main objective of the study was to examine the types of bullying that were taking place in the senior high schools in Ghana. A multi-stage sampling procedure, comprising purposive, simple random and snowball sampling technique, was used in the selection of the sample. A total of 354 respondents were drawn six schools in Ashanti, Central and…

The Influence of Support for Innovation on Organizational Innovation: Taking Organizational Learning as a Mediator

ERIC Educational Resources Information Center

Hsiao, Hsi-Chi; Chang, Jen-Chia; Chen, Su-Chang

2014-01-01

The purpose of this study was to examine the role of organizational learning as a mediator variable between support for innovation and organizational innovation. Samples for this study were randomly selected from 22 technological colleges in Taiwan. The final sample included 322 participants in the full sample which accounted for 58.42 % of the…

7 CFR 29.6104 - Rule 18.

Code of Federal Regulations, 2014 CFR

2014-01-01

... INSPECTION Standards Rules § 29.6104 Rule 18. Burn shall be determined as the average burning time of leaves selected at random from the sample. A minimum of 10 leaves shall be selected as representative regardless... on the same side of the leaf. The leaf shall be punctured to permit quick ignition when placed over a...

7 CFR 29.6104 - Rule 18.

Code of Federal Regulations, 2010 CFR

2010-01-01

... INSPECTION Standards Rules § 29.6104 Rule 18. Burn shall be determined as the average burning time of leaves selected at random from the sample. A minimum of 10 leaves shall be selected as representative regardless... on the same side of the leaf. The leaf shall be punctured to permit quick ignition when placed over a...

7 CFR 29.6104 - Rule 18.

Code of Federal Regulations, 2013 CFR

2013-01-01

... INSPECTION Standards Rules § 29.6104 Rule 18. Burn shall be determined as the average burning time of leaves selected at random from the sample. A minimum of 10 leaves shall be selected as representative regardless... on the same side of the leaf. The leaf shall be punctured to permit quick ignition when placed over a...

7 CFR 29.6104 - Rule 18.

Code of Federal Regulations, 2011 CFR

2011-01-01

... INSPECTION Standards Rules § 29.6104 Rule 18. Burn shall be determined as the average burning time of leaves selected at random from the sample. A minimum of 10 leaves shall be selected as representative regardless... on the same side of the leaf. The leaf shall be punctured to permit quick ignition when placed over a...

7 CFR 29.6104 - Rule 18.

Code of Federal Regulations, 2012 CFR

2012-01-01

... INSPECTION Standards Rules § 29.6104 Rule 18. Burn shall be determined as the average burning time of leaves selected at random from the sample. A minimum of 10 leaves shall be selected as representative regardless... on the same side of the leaf. The leaf shall be punctured to permit quick ignition when placed over a...

Assessment of the Implementation of Continuous Assessment: The Case of METTU University

ERIC Educational Resources Information Center

Walde, Getinet Seifu

2016-01-01

This paper examines the status of the implementation of continuous assessment (CA) in Mettu University. A random stratified sampling method was used to select 309 students and 29 instructors and purposive method used to select quality assurance and faculty Deans. Questionnaires, focus group discussion, interview and documents were used for data…

Site Selection in Experiments: An Assessment of Site Recruitment and Generalizability in Two Scale-Up Studies

ERIC Educational Resources Information Center

Tipton, Elizabeth; Fellers, Lauren; Caverly, Sarah; Vaden-Kiernan, Michael; Borman, Geoffrey; Sullivan, Kate; Ruiz de Castilla, Veronica

2016-01-01

Recently, statisticians have begun developing methods to improve the generalizability of results from large-scale experiments in education. This work has included the development of methods for improved site selection when random sampling is infeasible, including the use of stratification and targeted recruitment strategies. This article provides…

A bayesian hierarchical model for classification with selection of functional predictors.

PubMed

Zhu, Hongxiao; Vannucci, Marina; Cox, Dennis D

2010-06-01

In functional data classification, functional observations are often contaminated by various systematic effects, such as random batch effects caused by device artifacts, or fixed effects caused by sample-related factors. These effects may lead to classification bias and thus should not be neglected. Another issue of concern is the selection of functions when predictors consist of multiple functions, some of which may be redundant. The above issues arise in a real data application where we use fluorescence spectroscopy to detect cervical precancer. In this article, we propose a Bayesian hierarchical model that takes into account random batch effects and selects effective functions among multiple functional predictors. Fixed effects or predictors in nonfunctional form are also included in the model. The dimension of the functional data is reduced through orthonormal basis expansion or functional principal components. For posterior sampling, we use a hybrid Metropolis-Hastings/Gibbs sampler, which suffers slow mixing. An evolutionary Monte Carlo algorithm is applied to improve the mixing. Simulation and real data application show that the proposed model provides accurate selection of functional predictors as well as good classification.

Two Extremely Red Galaxies

NASA Technical Reports Server (NTRS)

Joseph, Robert D.; Hora, Joseph; Stockton, Alan; Hu, Esther; Sanders, David

1997-01-01

This report concerns one of the major observational studies in the ISO Central Programme, the ISO Normal Galaxy Survey. This is a survey of an unbiased sample of spiral and lenticular galaxies selected from the Revised Shapley-Ames Catalog. It is therefore optically-selected, with a brightness limit of blue magnitude = 12, and otherwise randomly chosen. The original sample included 150 galaxies, but this was reduced to 74 when the allocated observing time was expended because the ISO overheads encountered in flight were much larger than predicted.

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

Bromberger, Seth A.; Klymko, Christine F.; Henderson, Keith A.

Betweenness centrality is a graph statistic used to nd vertices that are participants in a large number of shortest paths in a graph. This centrality measure is commonly used in path and network interdiction problems and its complete form requires the calculation of all-pairs shortest paths for each vertex. This leads to a time complexity of O(jV jjEj), which is impractical for large graphs. Estimation of betweenness centrality has focused on performing shortest-path calculations on a subset of randomly- selected vertices. This reduces the complexity of the centrality estimation to O(jSjjEj); jSj < jV j, which can be scaled appropriatelymore » based on the computing resources available. An estimation strategy that uses random selection of vertices for seed selection is fast and simple to implement, but may not provide optimal estimation of betweenness centrality when the number of samples is constrained. Our experimentation has identi ed a number of alternate seed-selection strategies that provide lower error than random selection in common scale-free graphs. These strategies are discussed and experimental results are presented.« less

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…

WORD FREQUENCY IN THE MODERN GERMAN SHORT STORY. FINAL REPORT.

ERIC Educational Resources Information Center

SCHERER, GEORGE A.; AND OTHERS

A LIST OF THE MOST FREQUENTLY USED WORDS IN MODERN GERMAN SHORT STORIES WAS COMPILED. AN ANTHOLOGY OF 702 RECENTLY PUBLISHED, GERMAN SHORT STORIES WAS OBTAINED AND USED FOR A WORD COUNT, INVOLVING THE RANDOM SELECTION OF 4 WORDS IN EVERY 100-WORD PASSAGE. TWO INDEPENDENT RANDOM SAMPLES OF ABOUT 80,000 WORDS EACH WERE DRAWN FROM NEARLY 2 MILLION…

Factual knowledge about AIDS and dating practices among high school students from selected schools.

PubMed

Nyachuru-Sihlangu, R H; Ndlovu, J

1992-06-01

Following various educational strategies by governmental and non-governmental organisations to educate youths and school teachers about HIV infection and prevention, this KABP survey was one attempt to evaluate the results. The study sample of 478 high school students was drawn from four randomly selected schools in Mashonaland and Matabeleland including high and low density, government and mission co-educational schools. The sample was randomly selected and stratified to represent sex and grade level. The KABP self administered questionnaire was used. The paper analyses the relationship between the knowledge and dating patterns. Generally, respondents demonstrated a 50pc to 80pc accuracy of factual knowledge. Of the 66pc Forms I through IV pupils who dated, 30pc preferred only sexually involved relationships and a small number considered the possibility of HIV/AIDS infection. A theoretically based tripartite coalition involving the school, the family health care services for education, guidance and support to promote responsible behaviour throughout childhood was suggested.

Different hunting strategies select for different weights in red deer.

PubMed

Martínez, María; Rodríguez-Vigal, Carlos; Jones, Owen R; Coulson, Tim; San Miguel, Alfonso

2005-09-22

Much insight can be derived from records of shot animals. Most researchers using such data assume that their data represents a random sample of a particular demographic class. However, hunters typically select a non-random subset of the population and hunting is, therefore, not a random process. Here, with red deer (Cervus elaphus) hunting data from a ranch in Toledo, Spain, we demonstrate that data collection methods have a significant influence upon the apparent relationship between age and weight. We argue that a failure to correct for such methodological bias may have significant consequences for the interpretation of analyses involving weight or correlated traits such as breeding success, and urge researchers to explore methods to identify and correct for such bias in their data.

Generation of kth-order random toposequences

NASA Astrophysics Data System (ADS)

Odgers, Nathan P.; McBratney, Alex. B.; Minasny, Budiman

2008-05-01

The model presented in this paper derives toposequences from a digital elevation model (DEM). It is written in ArcInfo Macro Language (AML). The toposequences are called kth-order random toposequences, because they take a random path uphill to the top of a hill and downhill to a stream or valley bottom from a randomly selected seed point, and they are located in a streamshed of order k according to a particular stream-ordering system. We define a kth-order streamshed as the area of land that drains directly to a stream segment of stream order k. The model attempts to optimise the spatial configuration of a set of derived toposequences iteratively by using simulated annealing to maximise the total sum of distances between each toposequence hilltop in the set. The user is able to select the order, k, of the derived toposequences. Toposequences are useful for determining soil sampling locations for use in collecting soil data for digital soil mapping applications. Sampling locations can be allocated according to equal elevation or equal-distance intervals along the length of the toposequence, for example. We demonstrate the use of this model for a study area in the Hunter Valley of New South Wales, Australia. Of the 64 toposequences derived, 32 were first-order random toposequences according to Strahler's stream-ordering system, and 32 were second-order random toposequences. The model that we present in this paper is an efficient method for sampling soil along soil toposequences. The soils along a toposequence are related to each other by the topography they are found in, so soil data collected by this method is useful for establishing soil-landscape rules for the preparation of digital soil maps.

[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.

Neither fixed nor random: weighted least squares meta-analysis.

PubMed

Stanley, T D; Doucouliagos, Hristos

2015-06-15

This study challenges two core conventional meta-analysis methods: fixed effect and random effects. We show how and explain why an unrestricted weighted least squares estimator is superior to conventional random-effects meta-analysis when there is publication (or small-sample) bias and better than a fixed-effect weighted average if there is heterogeneity. Statistical theory and simulations of effect sizes, log odds ratios and regression coefficients demonstrate that this unrestricted weighted least squares estimator provides satisfactory estimates and confidence intervals that are comparable to random effects when there is no publication (or small-sample) bias and identical to fixed-effect meta-analysis when there is no heterogeneity. When there is publication selection bias, the unrestricted weighted least squares approach dominates random effects; when there is excess heterogeneity, it is clearly superior to fixed-effect meta-analysis. In practical applications, an unrestricted weighted least squares weighted average will often provide superior estimates to both conventional fixed and random effects. Copyright © 2015 John Wiley & Sons, Ltd.

Thermal regimes of Mexican spotted owl nest stands

Treesearch

Joseph L. Ganey

2004-01-01

To evaluate the hypothesis that spotted owls (Strix occidentalis) select habitats with cool microclimates to avoid high daytime temperatures, I sampled thermal regimes in nest areas used by Mexican spotted owls (S. o. lucida) in northern Arizona. I sampled air temperature at 30-min intervals in 30 pairs of nest and random sites...

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…

A Study of Occupational Stress and Organizational Climate of Higher Secondary Teachers

ERIC Educational Resources Information Center

Benedicta, A. Sneha

2014-01-01

This study mainly aims to describe the occupational stress and organizational climate of higher secondary teachers with regard to gender, locality, family type, experience and type of management. Simple random sampling technique was adopted for the selection of sample. The data is collected from 200 higher secondary teachers from government and…

Value Orientation of Singapore Adolescents Towards Truthfulness, Justice and Compassion.

ERIC Educational Resources Information Center

Seng, SeokHoon; Siang, Low Meow; Wei, Tan Tai

This study examined the value orientation of Singapore adolescents toward the three fundamental values of truthfulness, justice, and compassion. A random sample of 315 secondary school students from 4 schools in Singapore (135 males and 180 females) completed a questionnaire, and a select sample of 19 students completed interviews about their…

Development of Effective Teacher Program: Teamwork Building Program for Thailand's Municipal Schools

ERIC Educational Resources Information Center

Chantathai, Pimpka; Tesaputa, Kowat; Somprach, Kanokorn

2015-01-01

This research is aimed to formulate the effective teacher teamwork program in municipal schools in Thailand. Primary survey on current situation and problem was conducted to develop the plan to suggest potential programs. Samples were randomly selected from municipal schools by using multi-stage sampling method in order to investigate their…

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…

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…

The Impact of Education on Rural Women's Participation in Political and Economic Activities

ERIC Educational Resources Information Center

Bishaw, Alemayehu

2014-01-01

This study endeavored to investigate the impact of education on rural women's participation in political and economic activities. Six hundred rural women and 12 gender Activists were selected for this study from three Zones of Amhara Region, Ethiopia using multi-stage random sampling technique and purposeful sampling techniques respectively.…

Influence of tree spatial pattern and sample plot type and size on inventory

Treesearch

John-Pascall Berrill; Kevin L. O' Hara

2012-01-01

Sampling with different plot types and sizes was simulated using tree location maps and data collected in three even-aged coast redwood (Sequoia sempervirens) stands selected to represent uniform, random, and clumped spatial patterns of tree locations. Fixed-radius circular plots, belt transects, and variable-radius plots were installed by...

Academic Optimism and Organizational Citizenship Behaviour amongst Secondary School Teachers

ERIC Educational Resources Information Center

Makvandi, Abdollah; Naderi, Farah; Makvandi, Behnam; Pasha, Reza; Ehteshamzadeh, Parvin

2018-01-01

The purpose of the study was to investigate the simple and multiple relationships between academic optimism and organizational-citizenship behavior amongst high school teachers in Ramhormoz, Iran. The sample consisted of 250 (125 female and 125 male) teachers, selected by stratified random sampling in 2016- 2017. The measurement tools included…

Motivational Factors and Teachers Commitment in Public Secondary Schools in Mbale Municipality

ERIC Educational Resources Information Center

Olurotimi, Ogunlade Joseph; Asad, Kamonges Wahab; Abdulrauf, Abdulkadir

2015-01-01

The study investigated the influence of motivational factors on teachers' commitment in public Secondary School in Mbale Municipality. The study employed Cross-sectional survey design. The sampling technique used to select was simple random sampling technique. The instrument used to collect data was a self designed questionnaire. The data…

Development and Validation of Academic Dishonesty Scale (ADS): Presenting a Multidimensional Scale

ERIC Educational Resources Information Center

Bashir, Hilal; Bala, Ranjan

2018-01-01

The purpose of the study was to develop a scale measuring academic dishonesty of undergraduate students. The sample of the study constitutes nine hundred undergraduate students selected via random sampling technique. After receiving expert's opinions for the face and content validity of the scale, the exploratory factor analysis (EFA) and…

Los Angeles Community College District Fall 1996 Student Survey.

ERIC Educational Resources Information Center

Prather, George; Kelly, Dexter

This report presents the results of the 1996 Los Angeles Community College District Student Survey. The survey was administered in a randomly selected group of classes. Each college sample is independent of the others and the proportion of students sampled within each college will vary. Responses were weighted inversely to account for…

Effects of prey abundance, distribution, visual contrast and morphology on selection by a pelagic piscivore

USGS Publications Warehouse

Hansen, Adam G.; Beauchamp, David A.

2014-01-01

Most predators eat only a subset of possible prey. However, studies evaluating diet selection rarely measure prey availability in a manner that accounts for temporal–spatial overlap with predators, the sensory mechanisms employed to detect prey, and constraints on prey capture.We evaluated the diet selection of cutthroat trout (Oncorhynchus clarkii) feeding on a diverse planktivore assemblage in Lake Washington to test the hypothesis that the diet selection of piscivores would reflect random (opportunistic) as opposed to non-random (targeted) feeding, after accounting for predator–prey overlap, visual detection and capture constraints.Diets of cutthroat trout were sampled in autumn 2005, when the abundance of transparent, age-0 longfin smelt (Spirinchus thaleichthys) was low, and 2006, when the abundance of smelt was nearly seven times higher. Diet selection was evaluated separately using depth-integrated and depth-specific (accounted for predator–prey overlap) prey abundance. The abundance of different prey was then adjusted for differences in detectability and vulnerability to predation to see whether these factors could explain diet selection.In 2005, cutthroat trout fed non-randomly by selecting against the smaller, transparent age-0 longfin smelt, but for the larger age-1 longfin smelt. After adjusting prey abundance for visual detection and capture, cutthroat trout fed randomly. In 2006, depth-integrated and depth-specific abundance explained the diets of cutthroat trout well, indicating random feeding. Feeding became non-random after adjusting for visual detection and capture. Cutthroat trout selected strongly for age-0 longfin smelt, but against similar sized threespine stickleback (Gasterosteus aculeatus) and larger age-1 longfin smelt in 2006. Overlap with juvenile sockeye salmon (O. nerka) was minimal in both years, and sockeye salmon were rare in the diets of cutthroat trout.The direction of the shift between random and non-random selection depended on the presence of a weak versus a strong year class of age-0 longfin smelt. These fish were easy to catch, but hard to see. When their density was low, poor detection could explain their rarity in the diet. When their density was high, poor detection was compensated by higher encounter rates with cutthroat trout, sufficient to elicit a targeted feeding response. The nature of the feeding selectivity of a predator can be highly dependent on fluctuations in the abundance and suitability of key prey.

The impact of traffic sign deficit on road traffic accidents in Nigeria.

PubMed

Ezeibe, Christian; Ilo, Chukwudi; Oguonu, Chika; Ali, Alphonsus; Abada, Ifeanyi; Ezeibe, Ezinwanne; Oguonu, Chukwunonso; Abada, Felicia; Izueke, Edwin; Agbo, Humphrey

2018-04-04

This study assesses the impact of traffic sign deficit on road traffic accidents in Nigeria. The participants were 720 commercial vehicle drivers. While simple random sampling was used to select 6 out of 137 federal highways, stratified random sampling was used to select six categories of commercial vehicle drivers. The study used qual-dominant mixed methods approach comprising key informant interviews; group interviews; field observation; policy appraisal and secondary literature on traffic signs. Result shows that the failure of government to provide and maintain traffic signs in order to guide road users through the numerous accident black spots on the highways is the major cause of road accidents in Nigeria. The study argues that provision and maintenance of traffic signs present opportunity to promoting safety on the highways and achieving the sustainable development goals.

An Empirically Derived Taxonomy for Personality Diagnosis: Bridging Science and Practice in Conceptualizing Personality

PubMed Central

Westen, Drew; Shedler, Jonathan; Bradley, Bekh; DeFife, Jared A.

2013-01-01

Objective The authors describe a system for diagnosing personality pathology that is empirically derived, clinically relevant, and practical for day-to-day use. Method A random national sample of psychiatrists and clinical psychologists (N=1,201) described a randomly selected current patient with any degree of personality dysfunction (from minimal to severe) using the descriptors in the Shedler-Westen Assessment Procedure–II and completed additional research forms. Results The authors applied factor analysis to identify naturally occurring diagnostic groupings within the patient sample. The analysis yielded 10 clinically coherent personality diagnoses organized into three higher-order clusters: internalizing, externalizing, and borderline-dysregulated. The authors selected the most highly rated descriptors to construct a diagnostic prototype for each personality syndrome. In a second, independent sample, research interviewers and patients’ treating clinicians were able to diagnose the personality syndromes with high agreement and minimal comorbidity among diagnoses. Conclusions The empirically derived personality prototypes described here provide a framework for personality diagnosis that is both empirically based and clinically relevant. PMID:22193534

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.

Guided transect sampling - a new design combining prior information and field surveying

Treesearch

Anna Ringvall; Goran Stahl; Tomas Lamas

2000-01-01

Guided transect sampling is a two-stage sampling design in which prior information is used to guide the field survey in the second stage. In the first stage, broad strips are randomly selected and divided into grid-cells. For each cell a covariate value is estimated from remote sensing data, for example. The covariate is the basis for subsampling of a transect through...

Ground sample data for the Conterminous U.S. Land Cover Characteristics Database

Treesearch

Robert Burgan; Colin Hardy; Donald Ohlen; Gene Fosnight; Robert Treder

1999-01-01

Ground sample data were collected for a land cover database and raster map that portray 159 vegetation classes at 1 km2 resolution for the conterminous United States. Locations for 3,500 1 km2 ground sample plots were selected randomly across the United States. The number of plots representing each vegetation class was weighted by the proportionate coverage of each...

Problems Accompanied Individuals with Learning Disability and Its Relationship to Gender and Family Economic Status Variables in a Jordanian Sample

ERIC Educational Resources Information Center

Al-Oweidi, Alia M.

2015-01-01

The purpose of this study is to investigate the relationship between problems that accompany individuals with learning disability and the variables of gender and family economic status for a selected sample of Jordanians. The sample of the study, which consisted of (239) male and female students, was chosen randomly. To achieve this aim, the…

People's Need for Additional Job Training: Development and Evaluation of an Assessment Procedure.

ERIC Educational Resources Information Center

Copa, George H.; Maurice, Clyde F.

A procedure was developed and evaluated for assessing the self-perceived educational needs of people as one input to the process of planning, approving, and implementing relevant educational programs. The method of data collection involved selecting samples of people by randomly selecting households in a given geographic area, and then contacting…

Identification of the Social Development in Early Childhood in Pakistan

ERIC Educational Resources Information Center

Malik, Asif; Sarwar, Muhammad; Khan, Naeemullah

2010-01-01

This study was conducted to identify the social development in early childhood years. It was delimited to eight private schools of Lahore City from the area of Faisal Town and Shadman. Forty students (male and female) were randomly selected as the sample. Five students from Nursery, Prep and grade one were selected from each school. A checklist…

Creating an Awareness of Alternatives to Psycho-Social Situations in Elementary School Children.

ERIC Educational Resources Information Center

LeCapitaine, John E.

This study was designed to determine the effectiveness of 18 selected lessons from Dupont's Toward Affective Development (TAD) program for creating an awareness in students of alternatives to psycho-social situations. Using a sample of 60 subjects randomly selected from 111 sixth-grade students in northwest Wisconsin, two experimental and two…

An overview of the Columbia Habitat Monitoring Program's (CHaMP) spatial-temporal design framework

EPA Science Inventory

We briefly review the concept of a master sample applied to stream networks in which a randomized set of stream sites is selected across a broad region to serve as a list of sites from which a subset of sites is selected to achieve multiple objectives of specific designs. The Col...

Employment Opportunities and Competencies Needed in Farm Occupations in Selected Counties in Kentucky.

ERIC Educational Resources Information Center

Neel, C.O., Jr.

To identify present and emerging farm occupations and necessary competencies, personal interviews were conducted by teachers of agriculture with a random sample of 329 farm operators in 11 selected counties in Kentucky. Slightly more than 75 percent of the operators interviewed were owners living on a farm. Some population characteristics were:…

Extrinsic Motivation as Correlates of Work Attitude of the Nigerian Police Force: Implications for Counselling

ERIC Educational Resources Information Center

Igun, Sylvester Nosakhare

2008-01-01

The study examined Extrinsic motivation as correlates of work attitude of the Nigeria Police Force and its implications for counselling. 300 Police personnel were selected by random sampling technique from six departments that make up police force Headquarters, Abuja. The personnel were selected from each department using simple sampling…

The Interrelationships of Preadolescents' Student Characteristics Influencing Selection of Career Exploration Courses [And Abstract]. Industrial Arts Education Monograph No. 1.

ERIC Educational Resources Information Center

Meehan, Merrill L.

The study investigated the interaction of personal and environmental factors influencing seventh graders' selection of career exploration courses for increased exploration in the eighth grade. A stratified random sample (496 students) was drawn from the Pittsburgh Public School's Occupational, Vocational, and Technical Exploratory Program.…

Moderate Physical Activity and Its Relationship to Select Measures of a Healthy Diet

ERIC Educational Resources Information Center

Blakely, Frank; Dunnagan, Tim; Haynes, George; Moore, Sylvia; Pelican, Suzanne

2004-01-01

In rural communities, physical activity may influence and predict nutritional behaviors. The purpose of this investigation was to determine if an individual's stage of participation in moderate physical activity was related to select measures of a healthy diet. Data were collected using a mail-in survey from a random sample conducted in the…

Factors That Predict Negative Versus Positive Addictions in Offspring: Are Dependent Exercisers Different Than Victims of Other Addictions?

ERIC Educational Resources Information Center

Manning, Terri M.

The study reported here assessed individuals' selection of excessive exercise dependent behaviors as they relate to self-esteem, family environment, and perceptions of family members exhibiting dysfunctional behaviors or addictions. A survey was taken of exercisers from a stratified random sample of competitive triathletes selected from the…

Applied Math & Science Levels Utilized in Selected Trade & Industrial Vocational Education. Final Report.

ERIC Educational Resources Information Center

Gray, James R.

Research identified and evaluated the level of applied mathematics and science used in selected trade and industrial (T&I) subjects taught in the Kentucky Vocational Education System. The random sample was composed of 52 programs: 21 carpentry, 20 electricity/electronics, and 11 machine shop. The 96 math content items that were identified as…

Generation of Aptamers from A Primer-Free Randomized ssDNA Library Using Magnetic-Assisted Rapid Aptamer Selection

NASA Astrophysics Data System (ADS)

Tsao, Shih-Ming; Lai, Ji-Ching; Horng, Horng-Er; Liu, Tu-Chen; Hong, Chin-Yih

2017-04-01

Aptamers are oligonucleotides that can bind to specific target molecules. Most aptamers are generated using random libraries in the standard systematic evolution of ligands by exponential enrichment (SELEX). Each random library contains oligonucleotides with a randomized central region and two fixed primer regions at both ends. The fixed primer regions are necessary for amplifying target-bound sequences by PCR. However, these extra-sequences may cause non-specific bindings, which potentially interfere with good binding for random sequences. The Magnetic-Assisted Rapid Aptamer Selection (MARAS) is a newly developed protocol for generating single-strand DNA aptamers. No repeat selection cycle is required in the protocol. This study proposes and demonstrates a method to isolate aptamers for C-reactive proteins (CRP) from a randomized ssDNA library containing no fixed sequences at 5‧ and 3‧ termini using the MARAS platform. Furthermore, the isolated primer-free aptamer was sequenced and binding affinity for CRP was analyzed. The specificity of the obtained aptamer was validated using blind serum samples. The result was consistent with monoclonal antibody-based nephelometry analysis, which indicated that a primer-free aptamer has high specificity toward targets. MARAS is a feasible platform for efficiently generating primer-free aptamers for clinical diagnoses.

Decision tree modeling using R.

PubMed

Zhang, Zhongheng

2016-08-01

In machine learning field, decision tree learner is powerful and easy to interpret. It employs recursive binary partitioning algorithm that splits the sample in partitioning variable with the strongest association with the response variable. The process continues until some stopping criteria are met. In the example I focus on conditional inference tree, which incorporates tree-structured regression models into conditional inference procedures. While growing a single tree is subject to small changes in the training data, random forests procedure is introduced to address this problem. The sources of diversity for random forests come from the random sampling and restricted set of input variables to be selected. Finally, I introduce R functions to perform model based recursive partitioning. This method incorporates recursive partitioning into conventional parametric model building.

The 1989 Georgia Survey of Adolescent Drug and Alcohol Use. Volume I: The Narrative Report for Survey Findings.

ERIC Educational Resources Information Center

Adams, Ronald D.; And Others

The 1989 Georgia Survey of Adolescent Drug and Alcohol Use was conducted in 373 schools throughout Georgia. The stratified random sample was obtained from schools that participated in the 1987 survey (in which 93% of the school systems in Georgia participated) and were selected randomly from strata based on size of community and geographic…

SAMPLING OSCILLOSCOPE

DOEpatents

Sugarman, R.M.

1960-08-30

An oscilloscope is designed for displaying transient signal waveforms having random time and amplitude distributions. The oscilloscopc is a sampling device that selects for display a portion of only those waveforms having a particular range of amplitudes. For this purpose a pulse-height analyzer is provided to screen the pulses. A variable voltage-level shifter and a time-scale rampvoltage generator take the pulse height relative to the start of the waveform. The variable voltage shifter produces a voltage level raised one step for each sequential signal waveform to be sampled and this results in an unsmeared record of input signal waveforms. Appropriate delay devices permit each sample waveform to pass its peak amplitude before the circuit selects it for display.

Effectiveness of a new health care organization model in primary care for chronic cardiovascular disease patients based on a multifactorial intervention: the PROPRESE randomized controlled trial.

PubMed

Orozco-Beltran, Domingo; Ruescas-Escolano, Esther; Navarro-Palazón, Ana Isabel; Cordero, Alberto; Gaubert-Tortosa, María; Navarro-Perez, Jorge; Carratalá-Munuera, Concepción; Pertusa-Martínez, Salvador; Soler-Bahilo, Enrique; Brotons-Muntó, Francisco; Bort-Cubero, Jose; Nuñez-Martinez, Miguel Angel; Bertomeu-Martinez, Vicente; Gil-Guillen, Vicente Francisco

2013-08-02

To evaluate the effectiveness of a new multifactorial intervention to improve health care for chronic ischemic heart disease patients in primary care. The strategy has two components: a) organizational for the patient/professional relationship and b) training for professionals. Experimental study. Randomized clinical trial. Follow-up period: one year. primary care, multicenter (15 health centers). For the intervention group 15 health centers are selected from those participating in ESCARVAL study. Once the center agreed to participate patients are randomly selected from the total amount of patients with ischemic heart disease registered in the electronic health records. For the control group a random sample of patients with ischemic heart disease is selected from all 72 health centers electronic records. This study aims to evaluate the efficacy of a multifactorial intervention strategy involving patients with ischemic heart disease for the improvement of the degree of control of the cardiovascular risk factors and of the quality of life, number of visits, and number of hospitalizations. NCT01826929.

Selective detection of underivatized 2,4-dichlorophenoxyacetic acid in soil by supercritical fluid chromatography with ion mobility detection.

PubMed

Morrissey, M A; Hill, H H

1989-09-01

A simplified procedure was developed for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D) in soils. Soil samples were separated by supercritical fluid chromatography after extraction without derivatization and without the use of column chromatography for cleanup. Interferences in the chromatographic separation were eliminated by using a tunably selective ion mobility detector. An atmospheric pressure ion formed by the free acid was selectively monitored so the detector could monitor 2,4-D in the presence of other electron-capturing compounds. For a randomly chosen soil sample, the level of 2,4-D detected was estimated at 500 ppb.

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.

Public Participation Guide: Citizen Juries

EPA Pesticide Factsheets

Citizen juries involve creating a “jury” a representative sample of citizens (usually selected in a random or stratified manner) who are briefed in detail on the background and current thinking relating to a particular issue or project.

Drug use among drivers

DOT National Transportation Integrated Search

1975-02-01

Randomly selected drivers were stopped at times and places of previous fatal crashes in Lincoln, Nebraska, and Dade County (Miami), Florida. Breath, urnine, blood, and lip swab samples were requested, for later analysis for drugs and medications. A c...

Changing friend selection in middle school: A social network analysis of a randomized intervention study designed to prevent adolescent problem behavior

PubMed Central

DeLay, Dawn; Ha, Thao; Van Ryzin, Mark; Winter, Charlotte; Dishion, Thomas J.

2015-01-01

Adolescent friendships that promote problem behavior are often chosen in middle school. The current study examines the unintended impact of a randomized school based intervention on the selection of friends in middle school, as well as on observations of deviant talk with friends five years later. Participants included 998 middle school students (526 boys and 472 girls) recruited at the onset of middle school (age 11-12 years) from three public middle schools participating in the Family Check-up model intervention. The current study focuses only on the effects of the SHAPe curriculum—one level of the Family Check-up model—on friendship choices. Participants nominated friends and completed measures of deviant peer affiliation. Approximately half of the sample (n=500) was randomly assigned to the intervention and the other half (n=498) comprised the control group within each school. The results indicate that the SHAPe curriculum affected friend selection within School 1, but not within Schools 2 or 3. The effects of friend selection in School 1 translated into reductions in observed deviancy training five years later (age 16-17 years). By coupling longitudinal social network analysis with a randomized intervention study the current findings provide initial evidence that a randomized public middle school intervention can disrupt the formation of deviant peer groups and diminish levels of adolescent deviance five years later. PMID:26377235

Different hunting strategies select for different weights in red deer

PubMed Central

Martínez, María; Rodríguez-Vigal, Carlos; Jones, Owen R; Coulson, Tim; Miguel, Alfonso San

2005-01-01

Much insight can be derived from records of shot animals. Most researchers using such data assume that their data represents a random sample of a particular demographic class. However, hunters typically select a non-random subset of the population and hunting is, therefore, not a random process. Here, with red deer (Cervus elaphus) hunting data from a ranch in Toledo, Spain, we demonstrate that data collection methods have a significant influence upon the apparent relationship between age and weight. We argue that a failure to correct for such methodological bias may have significant consequences for the interpretation of analyses involving weight or correlated traits such as breeding success, and urge researchers to explore methods to identify and correct for such bias in their data. PMID:17148205

A Study of the Relationship between Demographic Factors and Elementary School Teacher Burnout: The Iranian Case

ERIC Educational Resources Information Center

Mazidi, Mohammad; Khoshbakht, Friba; Mahboobe, Alborzi

2017-01-01

The aim of the present study was to investigate the relationship between certain demographic factors and elementary school teachers' burnout. The sample consisted of 144 elementary school teachers (98 male and 76 women) selected through cluster random sampling. Data were collected by: (1) Personal Information Form developed by the researchers, and…

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…

Analyzing the Relationship between Positive Psychological Capital and Organizational Commitment of the Teachers

ERIC Educational Resources Information Center

Yalcin, Sinan

2016-01-01

In this study it was aimed to determine the relationship between teachers' positive psychological capital levels and organisational commitment. The study was conducted as a correlational survey which is one of the quantitative methods. The sample group consists of 244 teachers selected by using random sampling method among 1270 teachers working in…

Jackknifing Techniques for Evaluation of Equating Accuracy. Research Report. ETS RR-09-39

ERIC Educational Resources Information Center

Haberman, Shelby J.; Lee, Yi-Hsuan; Qian, Jiahe

2009-01-01

Grouped jackknifing may be used to evaluate the stability of equating procedures with respect to sampling error and with respect to changes in anchor selection. Properties of grouped jackknifing are reviewed for simple-random and stratified sampling, and its use is described for comparisons of anchor sets. Application is made to examples of item…

School Principals' Leadership Behaviours and Its Relation with Teachers' Sense of Self-Efficacy

ERIC Educational Resources Information Center

Mehdinezhad, Vali; Mansouri, Masoumeh

2016-01-01

The aim of this study was to investigate the relationship between school principals' leadership behaviours and teachers' sense of self-efficacy. The research method was descriptive and correlational. A sample size of 254 teachers was simply selected randomly by proportional sampling. For data collection, the Teachers' Sense of Efficacy Scale of…

The Relationship between Happiness, Subjective Well-Being, Creativity and Job Performance of Primary School Teachers in Ramhormoz City

ERIC Educational Resources Information Center

Jalali, Zohreh; Heidari, Alireza

2016-01-01

The research aimed to investigate the relationship between happiness, subjective well-being, creativity and job performance of primary school teachers in Ramhormoz City. Hence, a sample of 330 individuals was selected through random stratified sampling. The research tools included Oxford Happiness Inventory, Subjective Well-being Scale by Keyes…

Predicting Personality Resiliency by Psychological Well-Being and Its Components in Girl Students of Islamic Azad University

ERIC Educational Resources Information Center

Kajbafnezhad, Hadi; Khaneh Keshi, Ali

2015-01-01

The aim of this study was to predict psychological resilience by psychological well-being and its components. The research sample consisted of 216 girl students who were selected through multistage random sampling. The data were collected by implementing psychological resilience and psychological well-being questionnaire and analyzed by using…

Health Outcomes in Adolescence: Associations with Family, Friends and School Engagement

ERIC Educational Resources Information Center

Carter, Melissa; McGee, Rob; Taylor, Barry; Williams, Sheila

2007-01-01

Aim: To examine the associations between connectedness to family and friends, and school engagement, and selected health compromising and health promoting behaviours in a sample of New Zealand adolescents. Methods: A web-based survey was designed and administered to a random sample of 652 Year 11 students aged 16 years from all Dunedin (NZ) high…

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…

Dimensions of Oppositional Defiant Disorder in 3-Year-Old Preschoolers

ERIC Educational Resources Information Center

Ezpeleta, Lourdes; Granero, Roser; de la Osa, Nuria; Penelo, Eva; Domenech, Josep M.

2012-01-01

Background: To test the factor structure of oppositional defiant disorder (ODD) symptoms and to study the relationships between the proposed dimensions and external variables in a community sample of preschool children. Method: A sample of 1,341 3-year-old preschoolers was randomly selected and screened for a double-phase design. In total, 622…

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…

Using the Precaution Adoption Process Model to Describe a Disaster Preparedness Intervention among Low-Income Latinos

ERIC Educational Resources Information Center

Glik, Deborah C.; Eisenman, David P.; Zhou, Qiong; Tseng, Chi-Hong; Asch, Steven M.

2014-01-01

Only 40-50% of households in the United States are currently disaster prepared. In this intervention study, respondent-driven sampling was used to select a sample (n = 187) of low income, Latino residents of Los Angeles County, randomly assigned into two treatment conditions: (i) household preparedness education received through…

The Matrix Analogies Test: A Validity Study with the K-ABC.

ERIC Educational Resources Information Center

Smith, Douglas K.

The Matrix Analogies Test-Expanded Form (MAT-EF) and Kaufman Assessment Battery for Children (K-ABC) were administered in counterbalanced order to two randomly selected samples of students in grades 2 through 5. The MAT-EF was recently developed to measure non-verbal reasoning. The samples included 26 non-handicapped second graders in a rural…

Service Quality of State Universities in Turkey: The Case of Ankara

ERIC Educational Resources Information Center

Eres, Figen

2011-01-01

The aim of this study is determine the service quality perceptions of students being educated at state universities in Ankara. The sample of the study is composed of final grade students of faculties of Economics and Administrative Sciences. The sample of the study is composed of a total of randomly selected students. There were 416 returned…

Teaching Aptitude of Student Teachers and their Academic Achievements at Graduate Level

ERIC Educational Resources Information Center

Sajan, K. S.

2010-01-01

The present investigation aims at studying teaching aptitude of student teachers with respect to their gender and academic achievement at graduate level examination. The sample for this study is selected by stratified random sampling from the Teacher Education institutions of Malabar area of Kerala. Teaching Aptitude Test Battery (T A T B)…

Early Schooling: The Handicap of Being Poor and Male

ERIC Educational Resources Information Center

Entwisle, Doris R.; Alexander, Karl L.; Olson, Linda S.

2007-01-01

In trying to understand the origin of gender differences favoring girls in reading skills, analysts have examined mainly the performance of students who are in the same grade, with samples pooled across socioeconomic status (SES). Using a longitudinal sample in Baltimore, where all students in a randomly selected panel are the same age and are…

Problems of Female School Teachers in District Kulgam (J&K)

ERIC Educational Resources Information Center

Rashid, Ruhee; Maharashi, Santosh Kumar

2015-01-01

The purpose of this study is to find the problems of employed female school teachers in district Kulgam. Sample of 100 employed women are selected from different education institutions as 20 Rehaber e Taleem (ReT) female teachers, 40 female teachers, 20 female masters and 20 female lecturers using stratified random sampling. In this study we use…

Quantitative comparison of randomization designs in sequential clinical trials based on treatment balance and allocation randomness.

PubMed

Zhao, Wenle; Weng, Yanqiu; Wu, Qi; Palesch, Yuko

2012-01-01

To evaluate the performance of randomization designs under various parameter settings and trial sample sizes, and identify optimal designs with respect to both treatment imbalance and allocation randomness, we evaluate 260 design scenarios from 14 randomization designs under 15 sample sizes range from 10 to 300, using three measures for imbalance and three measures for randomness. The maximum absolute imbalance and the correct guess (CG) probability are selected to assess the trade-off performance of each randomization design. As measured by the maximum absolute imbalance and the CG probability, we found that performances of the 14 randomization designs are located in a closed region with the upper boundary (worst case) given by Efron's biased coin design (BCD) and the lower boundary (best case) from the Soares and Wu's big stick design (BSD). Designs close to the lower boundary provide a smaller imbalance and a higher randomness than designs close to the upper boundary. Our research suggested that optimization of randomization design is possible based on quantified evaluation of imbalance and randomness. Based on the maximum imbalance and CG probability, the BSD, Chen's biased coin design with imbalance tolerance method, and Chen's Ehrenfest urn design perform better than popularly used permuted block design, EBCD, and Wei's urn design. Copyright © 2011 John Wiley & Sons, Ltd.

Feasibility of collecting 24-h urine to monitor sodium intake in the National Health and Nutrition Examination Survey123

PubMed Central

Terry, Ana L; Cogswell, Mary E; Wang, Chia-Yih; Chen, Te-Ching; Loria, Catherine M; Wright, Jacqueline D; Zhang, Xinli; Lacher, David A; Merritt, Robert K; Bowman, Barbara A

2016-01-01

Background: Twenty-four–hour urine sodium excretion is recommended for monitoring population sodium intake. Because of concerns about participation and completion, sodium excretion has not been collected previously in US nationally representative surveys. Objective: We assessed the feasibility of implementing 24-h urine collections as part of a nationally representative survey. Design: We selected a random half sample of nonpregnant US adults aged 20–69 y in 3 geographic locations of the 2013 NHANES. Participants received explicit instructions, started and ended the urine collection in a urine study mobile examination center, and answered questions about their collection. Among those with a complete 24-h urine collection, a random one-half were asked to collect a second 24-h urine sample. Sodium, potassium, chloride, and creatinine excretion were analyzed. Results: The final NHANES examination response rate for adults aged 20–69 y in these 3 study locations was 71%. Of those examined (n = 476), 282 (59%) were randomly selected to participate in the 24-h urine collection. Of these, 212 persons [75% of those selected for 24-h urine collection; 53% (equal to 71% × 75% of those selected for the NHANES)] collected a complete initial 24-h specimen and 92 persons (85% of 108 selected) collected a second complete 24-h urine sample. More men than women completed an initial collection (P = 0.04); otherwise, completion did not vary by sociodemographic characteristics, body mass index, education, or employment status for either collection. Mean 24-h urine volume and sodium excretion were 1964 ± 1228 mL and 3657 ± 2003 mg, respectively, for the first 24-h urine sample, and 2048 ± 1288 mL and 3773 ± 1891 mg, respectively, for the second collection. Conclusion: Given the 53% final component response rate and 75% completion rate, 24-h urine collections were deemed feasible and implemented in the NHANES 2014 on a subsample of adults aged 20–69 y to assess population sodium intake. This study was registered at clinicaltrials.gov as NCT02723682. PMID:27413136

The Private School Market in Kuwait: A Field Study on Educational Investment Behavior of Kuwaiti Families

ERIC Educational Resources Information Center

Alqahtani, Abdulmuhsen Ayedh

2014-01-01

The current study aims at exploring Kuwaiti families' educational investment behavior pursuant to the selection of a specific private school for their children from the private school market. Using the quantitative approach and the principles of marketing research, a survey was administered to a randomly selected sample of Kuwaiti families (n =…

A large-scale study of the random variability of a coding sequence: a study on the CFTR gene.

PubMed

Modiano, Guido; Bombieri, Cristina; Ciminelli, Bianca Maria; Belpinati, Francesca; Giorgi, Silvia; Georges, Marie des; Scotet, Virginie; Pompei, Fiorenza; Ciccacci, Cinzia; Guittard, Caroline; Audrézet, Marie Pierre; Begnini, Angela; Toepfer, Michael; Macek, Milan; Ferec, Claude; Claustres, Mireille; Pignatti, Pier Franco

2005-02-01

Coding single nucleotide substitutions (cSNSs) have been studied on hundreds of genes using small samples (n(g) approximately 100-150 genes). In the present investigation, a large random European population sample (average n(g) approximately 1500) was studied for a single gene, the CFTR (Cystic Fibrosis Transmembrane conductance Regulator). The nonsynonymous (NS) substitutions exhibited, in accordance with previous reports, a mean probability of being polymorphic (q > 0.005), much lower than that of the synonymous (S) substitutions, but they showed a similar rate of subpolymorphic (q < 0.005) variability. This indicates that, in autosomal genes that may have harmful recessive alleles (nonduplicated genes with important functions), genetic drift overwhelms selection in the subpolymorphic range of variability, making disadvantageous alleles behave as neutral. These results imply that the majority of the subpolymorphic nonsynonymous alleles of these genes are selectively negative or even pathogenic.

Wavelength Selection Method Based on Differential Evolution for Precise Quantitative Analysis Using Terahertz Time-Domain Spectroscopy.

PubMed

Li, Zhi; Chen, Weidong; Lian, Feiyu; Ge, Hongyi; Guan, Aihong

2017-12-01

Quantitative analysis of component mixtures is an important application of terahertz time-domain spectroscopy (THz-TDS) and has attracted broad interest in recent research. Although the accuracy of quantitative analysis using THz-TDS is affected by a host of factors, wavelength selection from the sample's THz absorption spectrum is the most crucial component. The raw spectrum consists of signals from the sample and scattering and other random disturbances that can critically influence the quantitative accuracy. For precise quantitative analysis using THz-TDS, the signal from the sample needs to be retained while the scattering and other noise sources are eliminated. In this paper, a novel wavelength selection method based on differential evolution (DE) is investigated. By performing quantitative experiments on a series of binary amino acid mixtures using THz-TDS, we demonstrate the efficacy of the DE-based wavelength selection method, which yields an error rate below 5%.

The Effectiveness of Conflict Maps and the V-Shape Teaching Method in Science Conceptual Change among Eighth-Grade Students in Jordan

ERIC Educational Resources Information Center

Bawaneh, Ali Khalid Ali; Zain, Ahmad Nurulazam Md; Ghazali, Munirah

2010-01-01

The purpose of the present study is to investigate the effectiveness of Conflict Maps and the V-Shape method as teaching methods in bringing about conceptual change in science among primary eighth-grade students in Jordan. A randomly selected sample (N = 63) from the Bani Kenana region North of Jordan was randomly assigned to the two teaching…

Quantity and quality of information, education and communication during antenatal visit at private and public sector hospitals of Bahawalpur, Pakistan.

PubMed

Mahar, Benazeer; Kumar, Ramesh; Rizvi, Narjis; Bahalkani, Habib Akhtar; Haq, Mahboobul; Soomro, Jamila

2012-01-01

Information, education and communication (IEC) by health care provider to pregnant woman during the antenatal visit are very crucial for healthier outcome of pregnancy. This study analysed the quality and quantity of antenatal visit at a private and a public hospital of Bahawalpur, Pakistan. An exit interview was conducted from 216 pregnant women by using validated, reliable and pre-tested adapted questionnaire. First sample was selected by simple random sampling, for rest of the sample selection systematic random sampling was adapted by selecting every 7th women for interview. Ethical considerations were taken. Average communication time among pregnant woman and her healthcare provider was 3 minute in public and 8 minutes in private hospital. IEC mainly focused on diet and nutrition in private (86%) and (53%) public, advice for family planning after delivery was discussed with 13% versus 7% in public and private setting. None of the respondents in both facilities got advice or counselling on breastfeeding and neonatal care. Birth preparedness components were discussed, woman in public and private hospital respectively. In both settings antenatal clients were not received information and education communication according to World Health Organization guidelines. Quality and quantity of IEC during antenatal care was found very poor in both public and private sector hospitals of urban Pakistan.

Modified Bat Algorithm for Feature Selection with the Wisconsin Diagnosis Breast Cancer (WDBC) Dataset

PubMed

Jeyasingh, Suganthi; Veluchamy, Malathi

2017-05-01

Early diagnosis of breast cancer is essential to save lives of patients. Usually, medical datasets include a large variety of data that can lead to confusion during diagnosis. The Knowledge Discovery on Database (KDD) process helps to improve efficiency. It requires elimination of inappropriate and repeated data from the dataset before final diagnosis. This can be done using any of the feature selection algorithms available in data mining. Feature selection is considered as a vital step to increase the classification accuracy. This paper proposes a Modified Bat Algorithm (MBA) for feature selection to eliminate irrelevant features from an original dataset. The Bat algorithm was modified using simple random sampling to select the random instances from the dataset. Ranking was with the global best features to recognize the predominant features available in the dataset. The selected features are used to train a Random Forest (RF) classification algorithm. The MBA feature selection algorithm enhanced the classification accuracy of RF in identifying the occurrence of breast cancer. The Wisconsin Diagnosis Breast Cancer Dataset (WDBC) was used for estimating the performance analysis of the proposed MBA feature selection algorithm. The proposed algorithm achieved better performance in terms of Kappa statistic, Mathew’s Correlation Coefficient, Precision, F-measure, Recall, Mean Absolute Error (MAE), Root Mean Square Error (RMSE), Relative Absolute Error (RAE) and Root Relative Squared Error (RRSE). Creative Commons Attribution License

Model selection with multiple regression on distance matrices leads to incorrect inferences.

PubMed

Franckowiak, Ryan P; Panasci, Michael; Jarvis, Karl J; Acuña-Rodriguez, Ian S; Landguth, Erin L; Fortin, Marie-Josée; Wagner, Helene H

2017-01-01

In landscape genetics, model selection procedures based on Information Theoretic and Bayesian principles have been used with multiple regression on distance matrices (MRM) to test the relationship between multiple vectors of pairwise genetic, geographic, and environmental distance. Using Monte Carlo simulations, we examined the ability of model selection criteria based on Akaike's information criterion (AIC), its small-sample correction (AICc), and the Bayesian information criterion (BIC) to reliably rank candidate models when applied with MRM while varying the sample size. The results showed a serious problem: all three criteria exhibit a systematic bias toward selecting unnecessarily complex models containing spurious random variables and erroneously suggest a high level of support for the incorrectly ranked best model. These problems effectively increased with increasing sample size. The failure of AIC, AICc, and BIC was likely driven by the inflated sample size and different sum-of-squares partitioned by MRM, and the resulting effect on delta values. Based on these findings, we strongly discourage the continued application of AIC, AICc, and BIC for model selection with MRM.

Caries status in 16 year-olds with varying exposure to water fluoridation in Ireland.

PubMed

Mullen, J; McGaffin, J; Farvardin, N; Brightman, S; Haire, C; Freeman, R

2012-12-01

Most of the Republic of Ireland's public water supplies have been fluoridated since the mid-1960s while Northern Ireland has never been fluoridated, apart from some small short-lived schemes in east Ulster. This study examines dental caries status in 16 year-olds in a part of Ireland straddling fluoridated and non-fluoridated water supply areas and compares two methods of assessing the effectiveness of water fluoridation. The cross-sectional survey tested differences in caries status by two methods: 1, Estimated Fluoridation Status as used previously in national and regional studies in the Republic and in the All-Island study of 2002; 2, Percentage Lifetime Exposure, a modification of a system described by Slade in 1995 and used in Australian caries research. Adolescents were selected for the study by a two-part random sampling process. Firstly, schools were selected in each area by creating three tiers based on school size, and selecting schools randomly from each tier. Then random sampling of 16-year-olds from these schools, based on a pre-set sampling fraction for each tier of schools. With both systems of measurement, significantly lower caries levels were found in those children with the greatest exposure to fluoridated water when compared to those with the least exposure. The survey provides further evidence of the effectiveness in reducing dental caries experience up to 16 years of age. The extra intricacies involved in using the Percentage Lifetime Exposure method did not provide much more information when compared to the simpler Estimated Fluoridation Status method.

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.

Designing a national soil erosion monitoring network for England and Wales

NASA Astrophysics Data System (ADS)

Lark, Murray; Rawlins, Barry; Anderson, Karen; Evans, Martin; Farrow, Luke; Glendell, Miriam; James, Mike; Rickson, Jane; Quine, Timothy; Quinton, John; Brazier, Richard

2014-05-01

Although soil erosion is recognised as a significant threat to sustainable land use and may be a priority for action in any forthcoming EU Soil Framework Directive, those responsible for setting national policy with respect to erosion are constrained by a lack of robust, representative, data at large spatial scales. This reflects the process-orientated nature of much soil erosion research. Recognising this limitation, The UK Department for Environment, Food and Rural Affairs (Defra) established a project to pilot a cost-effective framework for monitoring of soil erosion in England and Wales (E&W). The pilot will compare different soil erosion monitoring methods at a site scale and provide statistical information for the final design of the full national monitoring network that will: provide unbiased estimates of the spatial mean of soil erosion rate across E&W (tonnes ha-1 yr-1) for each of three land-use classes - arable and horticultural grassland upland and semi-natural habitats quantify the uncertainty of these estimates with confidence intervals. Probability (design-based) sampling provides most efficient unbiased estimates of spatial means. In this study, a 16 hectare area (a square of 400 x 400 m) positioned at the centre of a 1-km grid cell, selected at random from mapped land use across E&W, provided the sampling support for measurement of erosion rates, with at least 94% of the support area corresponding to the target land use classes. Very small or zero erosion rates likely to be encountered at many sites reduce the sampling efficiency and make it difficult to compare different methods of soil erosion monitoring. Therefore, to increase the proportion of samples with larger erosion rates without biasing our estimates, we increased the inclusion probability density in areas where the erosion rate is likely to be large by using stratified random sampling. First, each sampling domain (land use class in E&W) was divided into strata; e.g. two sub-domains within which, respectively, small or no erosion rates, and moderate or larger erosion rates are expected. Each stratum was then sampled independently and at random. The sample density need not be equal in the two strata, but is known and is accounted for in the estimation of the mean and its standard error. To divide the domains into strata we used information on slope angle, previous interpretation of erosion susceptibility of the soil associations that correspond to the soil map of E&W at 1:250 000 (Soil Survey of England and Wales, 1983), and visual interpretation of evidence of erosion from aerial photography. While each domain could be stratified on the basis of the first two criteria, air photo interpretation across the whole country was not feasible. For this reason we used a two-phase random sampling for stratification (TPRS) design (de Gruijter et al., 2006). First, we formed an initial random sample of 1-km grid cells from the target domain. Second, each cell was then allocated to a stratum on the basis of the three criteria. A subset of the selected cells from each stratum were then selected for field survey at random, with a specified sampling density for each stratum so as to increase the proportion of cells where moderate or larger erosion rates were expected. Once measurements of erosion have been made, an estimate of the spatial mean of the erosion rate over the target domain, its standard error and associated uncertainty can be calculated by an expression which accounts for the estimated proportions of the two strata within the initial random sample. de Gruijter, J.J., Brus, D.J., Biekens, M.F.P. & Knotters, M. 2006. Sampling for Natural Resource Monitoring. Springer, Berlin. Soil Survey of England and Wales. 1983 National Soil Map NATMAP Vector 1:250,000. National Soil Research Institute, Cranfield University.

Selection of forest canopy gaps by male Cerulean Warblers in West Virginia

USGS Publications Warehouse

Perkins, Kelly A.; Wood, Petra Bohall

2014-01-01

Forest openings, or canopy gaps, are an important resource for many forest songbirds, such as Cerulean Warblers (Setophaga cerulea). We examined canopy gap selection by this declining species to determine if male Cerulean Warblers selected particular sizes, vegetative heights, or types of gaps. We tested whether these parameters differed among territories, territory core areas, and randomly-placed sample plots. We used enhanced territory mapping techniques (burst sampling) to define habitat use within the territory. Canopy gap densities were higher within core areas of territories than within territories or random plots, indicating that Cerulean Warblers selected habitat within their territories with the highest gap densities. Selection of regenerating gaps with woody vegetation >12 m within the gap, and canopy heights >24 m surrounding the gap, occurred within territory core areas. These findings differed between two sites indicating that gap selection may vary based on forest structure. Differences were also found regarding the placement of territories with respect to gaps. Larger gaps, such as wildlife food plots, were located on the periphery of territories more often than other types and sizes of gaps, while smaller gaps, such as treefalls, were located within territory boundaries more often than expected. The creations of smaller canopy gaps, <100 m2, within dense stands are likely compatible with forest management for this species.

Sample size determination for bibliographic retrieval studies

PubMed Central

Yao, Xiaomei; Wilczynski, Nancy L; Walter, Stephen D; Haynes, R Brian

2008-01-01

Background Research for developing search strategies to retrieve high-quality clinical journal articles from MEDLINE is expensive and time-consuming. The objective of this study was to determine the minimal number of high-quality articles in a journal subset that would need to be hand-searched to update or create new MEDLINE search strategies for treatment, diagnosis, and prognosis studies. Methods The desired width of the 95% confidence intervals (W) for the lowest sensitivity among existing search strategies was used to calculate the number of high-quality articles needed to reliably update search strategies. New search strategies were derived in journal subsets formed by 2 approaches: random sampling of journals and top journals (having the most high-quality articles). The new strategies were tested in both the original large journal database and in a low-yielding journal (having few high-quality articles) subset. Results For treatment studies, if W was 10% or less for the lowest sensitivity among our existing search strategies, a subset of 15 randomly selected journals or 2 top journals were adequate for updating search strategies, based on each approach having at least 99 high-quality articles. The new strategies derived in 15 randomly selected journals or 2 top journals performed well in the original large journal database. Nevertheless, the new search strategies developed using the random sampling approach performed better than those developed using the top journal approach in a low-yielding journal subset. For studies of diagnosis and prognosis, no journal subset had enough high-quality articles to achieve the expected W (10%). Conclusion The approach of randomly sampling a small subset of journals that includes sufficient high-quality articles is an efficient way to update or create search strategies for high-quality articles on therapy in MEDLINE. The concentrations of diagnosis and prognosis articles are too low for this approach. PMID:18823538

Alcohol- and Drug-Involved Driving in the United States: Methodology for the 2007 National Roadside Survey

PubMed Central

Lacey, John H.; Kelley-Baker, Tara; Voas, Robert B.; Romano, Eduardo; Furr-Holden, C. Debra; Torres, Pedro; Berning, Amy

2013-01-01

This article describes the methodology used in the 2007 U.S. National Roadside Survey to estimate the prevalence of alcohol- and drug-impaired driving and alcohol- and drug-involved driving. This study involved randomly stopping drivers at 300 locations across the 48 continental U.S. states at sites selected through a stratified random sampling procedure. Data were collected during a 2-hour Friday daytime session at 60 locations and during 2-hour nighttime weekend periods at 240 locations. Both self-report and biological measures were taken. Biological measures included breath alcohol measurements from 9,413 respondents, oral fluid samples from 7,719 respondents, and blood samples from 3,276 respondents. PMID:21997324

Assessment of computer-related health problems among post-graduate nursing students.

PubMed

Khan, Shaheen Akhtar; Sharma, Veena

2013-01-01

The study was conducted to assess computer-related health problems among post-graduate nursing students and to develop a Self Instructional Module for prevention of computer-related health problems in a selected university situated in Delhi. A descriptive survey with co-relational design was adopted. A total of 97 samples were selected from different faculties of Jamia Hamdard by multi stage sampling with systematic random sampling technique. Among post-graduate students, majority of sample subjects had average compliance with computer-related ergonomics principles. As regards computer related health problems, majority of post graduate students had moderate computer-related health problems, Self Instructional Module developed for prevention of computer-related health problems was found to be acceptable by the post-graduate students.

Experimental Design in Clinical 'Omics Biomarker Discovery.

PubMed

Forshed, Jenny

2017-11-03

This tutorial highlights some issues in the experimental design of clinical 'omics biomarker discovery, how to avoid bias and get as true quantities as possible from biochemical analyses, and how to select samples to improve the chance of answering the clinical question at issue. This includes the importance of defining clinical aim and end point, knowing the variability in the results, randomization of samples, sample size, statistical power, and how to avoid confounding factors by including clinical data in the sample selection, that is, how to avoid unpleasant surprises at the point of statistical analysis. The aim of this Tutorial is to help translational clinical and preclinical biomarker candidate research and to improve the validity and potential of future biomarker candidate findings.

Image subsampling and point scoring approaches for large-scale marine benthic monitoring programs

NASA Astrophysics Data System (ADS)

Perkins, Nicholas R.; Foster, Scott D.; Hill, Nicole A.; Barrett, Neville S.

2016-07-01

Benthic imagery is an effective tool for quantitative description of ecologically and economically important benthic habitats and biota. The recent development of autonomous underwater vehicles (AUVs) allows surveying of spatial scales that were previously unfeasible. However, an AUV collects a large number of images, the scoring of which is time and labour intensive. There is a need to optimise the way that subsamples of imagery are chosen and scored to gain meaningful inferences for ecological monitoring studies. We examine the trade-off between the number of images selected within transects and the number of random points scored within images on the percent cover of target biota, the typical output of such monitoring programs. We also investigate the efficacy of various image selection approaches, such as systematic or random, on the bias and precision of cover estimates. We use simulated biotas that have varying size, abundance and distributional patterns. We find that a relatively small sampling effort is required to minimise bias. An increased precision for groups that are likely to be the focus of monitoring programs is best gained through increasing the number of images sampled rather than the number of points scored within images. For rare species, sampling using point count approaches is unlikely to provide sufficient precision, and alternative sampling approaches may need to be employed. The approach by which images are selected (simple random sampling, regularly spaced etc.) had no discernible effect on mean and variance estimates, regardless of the distributional pattern of biota. Field validation of our findings is provided through Monte Carlo resampling analysis of a previously scored benthic survey from temperate waters. We show that point count sampling approaches are capable of providing relatively precise cover estimates for candidate groups that are not overly rare. The amount of sampling required, in terms of both the number of images and number of points, varies with the abundance, size and distributional pattern of target biota. Therefore, we advocate either the incorporation of prior knowledge or the use of baseline surveys to establish key properties of intended target biota in the initial stages of monitoring programs.

Evaluation of a Class of Simple and Effective Uncertainty Methods for Sparse Samples of Random Variables and Functions

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

Romero, Vicente; Bonney, Matthew; Schroeder, Benjamin

When very few samples of a random quantity are available from a source distribution of unknown shape, it is usually not possible to accurately infer the exact distribution from which the data samples come. Under-estimation of important quantities such as response variance and failure probabilities can result. For many engineering purposes, including design and risk analysis, we attempt to avoid under-estimation with a strategy to conservatively estimate (bound) these types of quantities -- without being overly conservative -- when only a few samples of a random quantity are available from model predictions or replicate experiments. This report examines a classmore » of related sparse-data uncertainty representation and inference approaches that are relatively simple, inexpensive, and effective. Tradeoffs between the methods' conservatism, reliability, and risk versus number of data samples (cost) are quantified with multi-attribute metrics use d to assess method performance for conservative estimation of two representative quantities: central 95% of response; and 10 -4 probability of exceeding a response threshold in a tail of the distribution. Each method's performance is characterized with 10,000 random trials on a large number of diverse and challenging distributions. The best method and number of samples to use in a given circumstance depends on the uncertainty quantity to be estimated, the PDF character, and the desired reliability of bounding the true value. On the basis of this large data base and study, a strategy is proposed for selecting the method and number of samples for attaining reasonable credibility levels in bounding these types of quantities when sparse samples of random variables or functions are available from experiments or simulations.« less

Does On-the-Job Training Improve an Employee's Job Performance?

ERIC Educational Resources Information Center

Duff, Juanita

A study examined the link between on-the-job training (OJT) and job performance in a randomly selected sample of 50 skilled maintenance craftpersons employed by the city of Chicago. The sample was identified from the training sheets signed by 160 employees who participated in OJT in a 1-month period. The majority of the employees agreed with…

The Influence of Labeling the Vegetable Content of Snack Food on Children's Taste Preferences: A Pilot Study

ERIC Educational Resources Information Center

Pope, Lizzy; Wolf, Randi L.

2012-01-01

Objective: This pilot study examined whether informing children of the presence of vegetables in select snack food items alters taste preference. Methods: A random sample of 68 elementary and middle school children tasted identical pairs of 3 snack food items containing vegetables. In each pair, 1 sample's label included the food's vegetable (eg,…

Challenges to Successful Total Quality Management Implementation in Public Secondary Schools: A Case Study of Kohat District, Pakistan

ERIC Educational Resources Information Center

Suleman, Qaiser; Gul, Rizwana

2015-01-01

The current study explores the challenges faced by public secondary schools in successful implementation of total quality management (TQM) in Kohat District. A sample of 25 heads and 75 secondary school teachers selected from 25 public secondary schools through simple random sampling technique was used. Descriptive research designed was used and a…

The National Center on Indigenous Hawaiian Behavioral Health Study of Prevalence of Psychiatric Disorders in Native Hawaiian Adolescents

ERIC Educational Resources Information Center

Andrade, Naleen N.; Hishinuma, Earl S.; McDermott, John F., Jr.; Johnson, Ronald C.; Goebert, Deborah A.; Makini, George K., Jr.; Nahulu, Linda B.; Yuen, Noelle Y. C.; McArdle, John J.; Bell, Cathy K.; Carlton, Barry S.; Miyamoto, Robin H.; Nishimura, Stephanie T.; Else, Iwalani R. N.; Guerrero, Anthony P. S.; Darmal, Arsalan; Yates, Alayne; Waldron, Jane A.

2006-01-01

Objectives: The prevalence rates of disorders among a community-based sample of Hawaiian youths were determined and compared to previously published epidemiological studies. Method: Using a two-phase design, 7,317 adolescents were surveyed (60% participation rate), from which 619 were selected in a modified random sample during the 1992-1993 to…

The Effective Management of Primary Schools in Ekiti State, Nigeria: An Analytical Assessment

ERIC Educational Resources Information Center

Adeyemi, T. O.

2009-01-01

This study investigated the management of education in primary schools in Ekiti State, Nigeria. As a correlational research, the study population comprised all the 694 primary schools in the State. Out of this, a sample of 320 schools was selected through the stratified random sampling technique. Two instruments were used to collect data for the…

How Professionalized Is College Teaching? Norms and the Ideal of Service. ASHE Annual Meeting Paper.

ERIC Educational Resources Information Center

Braxton, John M.; Bayer, Alan E.

This study examined the behavioral expectations and norms for college and university faculty particularly whether they varied with respect to the level of commitment to teaching at different institutions and in different disciplines. A cluster sampling design was used to select a random sample of the population of faculty in biology, history,…

The Relationship between Temperament, Gender, and Behavioural Problems in Preschool Children

ERIC Educational Resources Information Center

Yoleri, Sibel

2014-01-01

The aim of this study is to examine the relationship between gender and the temperamental characteristics of children between the ages of five and six, as well as to assess their behavioural problems. The sample included 128 children selected by simple random sampling from 5-6 year old children, receiving preschool education in the city centre of…

Effect of Items Direction (Positive or Negative) on the Factorial Construction and Criterion Related Validity in Likert Scale

ERIC Educational Resources Information Center

Naji Qasem, Mamun Ali; Ahmad Gul, Showkeen Bilal

2014-01-01

The study was conducted to know the effect of items direction (positive or negative) on the factorial construction and criterion related validity in Likert scale. The descriptive survey research method was used for the study and the sample consisted of 510 undergraduate students selected by used random sampling technique. A scale developed by…

Influence of Head Teachers' General and Instructional Supervisory Practices on Teachers' Work Performance in Secondary Schools in Entebbe Municipality, Wakiso District, Uganda

ERIC Educational Resources Information Center

Jared, Nzabonimpa Buregeya

2011-01-01

The study examined the Influence of Secondary School Head Teachers' General and Instructional Supervisory Practices on Teachers' Work Performance. Qualitative and qualitative methods with a descriptive-correlational research approach were used in the study. Purposive sampling technique alongside random sampling technique was used to select the…

The Association between Adverse Childhood Experience (ACE) and School Success in Elementary School Children

ERIC Educational Resources Information Center

Blodgett, Christopher; Lanigan, Jane D.

2018-01-01

We explored the feasibility of using school personnel as reporters to examine the relationship between the level of adverse childhood experiences (ACEs) exposure in a nonclinical sample of public elementary schoolchildren and academic risk. We selected a random sample of 2,101 children from kindergarten through 6th grade classroom rosters at 10…

Survey Response in a Statewide Social Experiment: Differences in Being Located and Collaborating, by Race and Hispanic Origin

ERIC Educational Resources Information Center

Nam, Yunju; Mason, Lisa Reyes; Kim, Youngmi; Clancy, Margaret; Sherraden, Michael

2013-01-01

This study examined whether and how survey response differs by race and Hispanic origin, using data from birth certificates and survey administrative data for a large-scale statewide experiment. The sample consisted of mothers of infants selected from Oklahoma birth certificates using a stratified random sampling method (N = 7,111). This study…

The Mediatory Role of Exercise Self-Regulation in the Relationship between Personality Traits and Anger Management of Athletes

ERIC Educational Resources Information Center

Shahbazzadeh, Somayeh; Beliad, Mohammad Reza

2017-01-01

This study investigates the mediatory role of exercise self-regulation role in the relationship between personality traits and anger management among athletes. The statistical population of this study includes all athlete students of Shar-e Ghods College, among which 260 people were selected as sample using random sampling method. In addition, the…

RANdom SAmple Consensus (RANSAC) algorithm for material-informatics: application to photovoltaic solar cells.

PubMed

Kaspi, Omer; Yosipof, Abraham; Senderowitz, Hanoch

2017-06-06

An important aspect of chemoinformatics and material-informatics is the usage of machine learning algorithms to build Quantitative Structure Activity Relationship (QSAR) models. The RANdom SAmple Consensus (RANSAC) algorithm is a predictive modeling tool widely used in the image processing field for cleaning datasets from noise. RANSAC could be used as a "one stop shop" algorithm for developing and validating QSAR models, performing outlier removal, descriptors selection, model development and predictions for test set samples using applicability domain. For "future" predictions (i.e., for samples not included in the original test set) RANSAC provides a statistical estimate for the probability of obtaining reliable predictions, i.e., predictions within a pre-defined number of standard deviations from the true values. In this work we describe the first application of RNASAC in material informatics, focusing on the analysis of solar cells. We demonstrate that for three datasets representing different metal oxide (MO) based solar cell libraries RANSAC-derived models select descriptors previously shown to correlate with key photovoltaic properties and lead to good predictive statistics for these properties. These models were subsequently used to predict the properties of virtual solar cells libraries highlighting interesting dependencies of PV properties on MO compositions.

Random-access optical-resolution photoacoustic microscopy using a digital micromirror device

PubMed Central

Liang, Jinyang; Zhou, Yong; Winkler, Amy W.; Wang, Lidai; Maslov, Konstantin I.; Li, Chiye; Wang, Lihong V.

2013-01-01

We developed random-access optical-resolution photoacoustic microscopy using a digital micromirror device. This system can rapidly scan arbitrarily shaped regions of interest within a 40×40 μm2 imaging area with a lateral resolution of 3.6 μm. To identify a region of interest, a global structural image is first acquired, then the selected region is scanned. The random-access ability was demonstrated by imaging two static samples, a carbon fiber cross and a monolayer of red blood cells, with an acquisition rate up to 4 kilohertz. The system was then used to monitor blood flow in vivo in real time within user-selected capillaries in a mouse ear. By imaging only the capillary of interest, the frame rate was increased by up to 9.2 times. PMID:23903111

Random-access optical-resolution photoacoustic microscopy using a digital micromirror device.

PubMed

Liang, Jinyang; Zhou, Yong; Winkler, Amy W; Wang, Lidai; Maslov, Konstantin I; Li, Chiye; Wang, Lihong V

2013-08-01

We developed random-access optical-resolution photoacoustic microscopy using a digital micromirror device. This system can rapidly scan arbitrarily shaped regions of interest within a 40 μm×40 μm imaging area with a lateral resolution of 3.6 μm. To identify a region of interest, a global structural image is first acquired, then the selected region is scanned. The random-access ability was demonstrated by imaging two static samples, a carbon fiber cross and a monolayer of red blood cells, with an acquisition rate up to 4 kHz. The system was then used to monitor blood flow in vivo in real time within user-selected capillaries in a mouse ear. By imaging only the capillary of interest, the frame rate was increased by up to 9.2 times.

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.

Impact of Substance Abuse on Academic Performance among Adolescent Students of Colleges of Education in Kwara State, Nigeria

ERIC Educational Resources Information Center

Akanbi, Muritala Ishola; Augustina, Godwin; Theophilus, Anyio Bahago; Muritala, Muhammad; Ajiboye, Ajiboye Stephen

2015-01-01

The study investigated the impact of substance abuse on adolescent on academic performance in colleges of education in Kwara State. The design used for the study was the survey. A sample of 150 adolescent students was randomly selected form selected departments in three colleges of education in the State. A validated instrument, Drug Habit…

College Climate and Teacher-Trainee's Academic Work in Selected Colleges of Education in the Ashanti Region of Ghana

ERIC Educational Resources Information Center

Adjei, Augustine; Dontoh, Samuel; Baafi-Frimpong, Stephen

2017-01-01

The study aimed at investigating the extent to which College climate (Leadership roles/practices and Class size) impact on academic work of Teacher-trainees. A survey research design was used for the study because it involved a study of relatively large population who were purposively and randomly selected. A sample size of 322 out of the…

The Differential Effects of Selected Programs on the Performance, Degree of Satisfaction and Retention of Community College Women Students. Final Report.

ERIC Educational Resources Information Center

Gillie, Angelo C.

This study, by examining how female post-secondary students view themselves within their college environment, attempts to determine how education can become more relevant for these women. Random samples of freshmen women students from four community colleges were selected according to the type of program in which they were enrolled--human service,…

Influence of Learning Environment on Students' Academic Achievement in Mathematics: A Case Study of Some Selected Secondary Schools in Yobe State-Nigeria

ERIC Educational Resources Information Center

Shamaki, Timothy Ado

2015-01-01

The purpose of the study was to determine the influence of learning environment on students' academic achievement in mathematics at senior secondary school level. Thus the study investigated some components of learning environment and their possible influence on students' academic achievement in mathematics. A sample of 337 randomly selected SS II…

Use of Bayes theorem to correct size-specific sampling bias in growth data.

PubMed

Troynikov, V S

1999-03-01

The bayesian decomposition of posterior distribution was used to develop a likelihood function to correct bias in the estimates of population parameters from data collected randomly with size-specific selectivity. Positive distributions with time as a parameter were used for parametrization of growth data. Numerical illustrations are provided. The alternative applications of the likelihood to estimate selectivity parameters are discussed.

Matching soil salinization and cropping systems in communally managed irrigation schemes

NASA Astrophysics Data System (ADS)

Malota, Mphatso; Mchenga, Joshua

2018-03-01

Occurrence of soil salinization in irrigation schemes can be a good indicator to introduce high salt tolerant crops in irrigation schemes. This study assessed the level of soil salinization in a communally managed 233 ha Nkhate irrigation scheme in the Lower Shire Valley region of Malawi. Soil samples were collected within the 0-0.4 m soil depth from eight randomly selected irrigation blocks. Irrigation water samples were also collected from five randomly selected locations along the Nkhate River which supplies irrigation water to the scheme. Salinity of both the soil and the irrigation water samples was determined using an electrical conductivity (EC) meter. Analysis of the results indicated that even for very low salinity tolerant crops (ECi < 2 dS/m), the irrigation water was suitable for irrigation purposes. However, root-zone soil salinity profiles depicted that leaching of salts was not adequate and that the leaching requirement for the scheme needs to be relooked and always be adhered to during irrigation operation. The study concluded that the crop system at the scheme needs to be adjusted to match with prevailing soil and irrigation water salinity levels.

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.

PyCCF: Python Cross Correlation Function for reverberation mapping studies

NASA Astrophysics Data System (ADS)

Sun, Mouyuan; Grier, C. J.; Peterson, B. M.

2018-05-01

PyCCF emulates a Fortran program written by B. Peterson for use with reverberation mapping. The code cross correlates two light curves that are unevenly sampled using linear interpolation and measures the peak and centroid of the cross-correlation function. In addition, it is possible to run Monto Carlo iterations using flux randomization and random subset selection (RSS) to produce cross-correlation centroid distributions to estimate the uncertainties in the cross correlation results.

Neither fixed nor random: weighted least squares meta-regression.

PubMed

Stanley, T D; Doucouliagos, Hristos

2017-03-01

Our study revisits and challenges two core conventional meta-regression estimators: the prevalent use of 'mixed-effects' or random-effects meta-regression analysis and the correction of standard errors that defines fixed-effects meta-regression analysis (FE-MRA). We show how and explain why an unrestricted weighted least squares MRA (WLS-MRA) estimator is superior to conventional random-effects (or mixed-effects) meta-regression when there is publication (or small-sample) bias that is as good as FE-MRA in all cases and better than fixed effects in most practical applications. Simulations and statistical theory show that WLS-MRA provides satisfactory estimates of meta-regression coefficients that are practically equivalent to mixed effects or random effects when there is no publication bias. When there is publication selection bias, WLS-MRA always has smaller bias than mixed effects or random effects. In practical applications, an unrestricted WLS meta-regression is likely to give practically equivalent or superior estimates to fixed-effects, random-effects, and mixed-effects meta-regression approaches. However, random-effects meta-regression remains viable and perhaps somewhat preferable if selection for statistical significance (publication bias) can be ruled out and when random, additive normal heterogeneity is known to directly affect the 'true' regression coefficient. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Territory and nest site selection patterns by Grasshopper Sparrows in southeastern Arizona

USGS Publications Warehouse

Ruth, Janet M.; Skagen, Susan K.

2017-01-01

Grassland bird populations are showing some of the greatest rates of decline of any North American birds, prompting measures to protect and improve important habitat. We assessed how vegetation structure and composition, habitat features often targeted for management, affected territory and nest site selection by Grasshopper Sparrows (Ammodramus savannarum ammolegus) in southeastern Arizona. To identify features important to males establishing territories, we compared vegetation characteristics of known territories and random samples on 2 sites over 5 years. We examined habitat selection patterns of females by comparing characteristics of nest sites with territories over 3 years. Males selected territories in areas of sparser vegetation structure and more tall shrubs (>2 m) than random plots on the site with low shrub densities. Males did not select territories based on the proportion of exotic grasses. Females generally located nest sites in areas with lower small shrub (1–2 m tall) densities than territories overall when possible and preferentially selected native grasses for nest construction. Whether habitat selection was apparent depended upon the range of vegetation structure that was available. We identified an upper threshold above which grass structure seemed to be too high and dense for Grasshopper Sparrows. Our results suggest that some management that reduces vegetative structure may benefit this species in desert grasslands at the nest and territory scale. However, we did not assess initial male habitat selection at a broader landscape scale where their selection patterns may be different and could be influenced by vegetation density and structure outside the range of values sampled in this study.

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

Changing Friend Selection in Middle School: A Social Network Analysis of a Randomized Intervention Study Designed to Prevent Adolescent Problem Behavior.

PubMed

DeLay, Dawn; Ha, Thao; Van Ryzin, Mark; Winter, Charlotte; Dishion, Thomas J

2016-04-01

Adolescent friendships that promote problem behavior are often chosen in middle school. The current study examines the unintended impact of a randomized school-based intervention on the selection of friends in middle school, as well as on observations of deviant talk with friends 5 years later. Participants included 998 middle school students (526 boys and 472 girls) recruited at the onset of middle school (age 11-12 years) from three public middle schools participating in the Family Check-up model intervention. The current study focuses only on the effects of the SHAPe curriculum-one level of the Family Check-up model-on friendship choices. Participants nominated friends and completed measures of deviant peer affiliation. Approximately half of the sample (n = 500) was randomly assigned to the intervention, and the other half (n = 498) comprised the control group within each school. The results indicate that the SHAPe curriculum affected friend selection within school 1 but not within schools 2 or 3. The effects of friend selection in school 1 translated into reductions in observed deviancy training 5 years later (age 16-17 years). By coupling longitudinal social network analysis with a randomized intervention study, the current findings provide initial evidence that a randomized public middle school intervention can disrupt the formation of deviant peer groups and diminish levels of adolescent deviance 5 years later.

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).

Fuzziness-based active learning framework to enhance hyperspectral image classification performance for discriminative and generative classifiers

PubMed Central

2018-01-01

Hyperspectral image classification with a limited number of training samples without loss of accuracy is desirable, as collecting such data is often expensive and time-consuming. However, classifiers trained with limited samples usually end up with a large generalization error. To overcome the said problem, we propose a fuzziness-based active learning framework (FALF), in which we implement the idea of selecting optimal training samples to enhance generalization performance for two different kinds of classifiers, discriminative and generative (e.g. SVM and KNN). The optimal samples are selected by first estimating the boundary of each class and then calculating the fuzziness-based distance between each sample and the estimated class boundaries. Those samples that are at smaller distances from the boundaries and have higher fuzziness are chosen as target candidates for the training set. Through detailed experimentation on three publically available datasets, we showed that when trained with the proposed sample selection framework, both classifiers achieved higher classification accuracy and lower processing time with the small amount of training data as opposed to the case where the training samples were selected randomly. Our experiments demonstrate the effectiveness of our proposed method, which equates favorably with the state-of-the-art methods. PMID:29304512

Survey of rural, private wells. Statistical design

USGS Publications Warehouse

Mehnert, Edward; Schock, Susan C.; ,

1991-01-01

Half of Illinois' 38 million acres were planted in corn and soybeans in 1988. On the 19 million acres planted in corn and soybeans, approximately 1 million tons of nitrogen fertilizer and 50 million pounds of pesticides were applied. Because groundwater is the water supply for over 90 percent of rural Illinois, the occurrence of agricultural chemicals in groundwater in Illinois is of interest to the agricultural community, the public, and regulatory agencies. The occurrence of agricultural chemicals in groundwater is well documented. However, the extent of this contamination still needs to be defined. This can be done by randomly sampling wells across a geographic area. Key elements of a random, water-well sampling program for regional groundwater quality include the overall statistical design of the program, definition of the sample population, selection of wells to be sampled, and analysis of survey results. These elements must be consistent with the purpose for conducting the program; otherwise, the program will not provide the desired information. The need to carefully design and conduct a sampling program becomes readily apparent when one considers the high cost of collecting and analyzing a sample. For a random sampling program conducted in Illinois, the key elements, as well as the limitations imposed by available information, are described.

Knowledge, attitude, and practice (KAP) of food hygiene among schools students' in Majmaah city, Saudi Arabia.

PubMed

Almansour, Mohammed; Sami, Waqas; Al-Rashedy, Oliyan Shoqer; Alsaab, Rayan Saad; Alfayez, Abdulrahman Saad; Almarri, Nawaf Rashed

2016-04-01

To determine the level of knowledge, attitude, and practice of food hygiene among primary, intermediate and high school students and explore association, if any, with socio-demographic differences. The observational cross-sectional study was conducted at boy's schools in Majmaah, Kingdom of Saudi Arabia, from February to May 2014. Data was collected using stratified random sampling technique from students aged 8-25 year. Two schools from each level (primary, intermediate and high school) were randomly selected and data was collected from the selected schools using simple random sampling method. A self-administered modified Sharif and Al-Malki questionnaire for knowledge, attitude and practice of food hygiene was used with Arabic translation. The mean age of 377 male students in the study was 14.53±2.647 years. Knowledge levels was less in primary school students compared to high school students (p=0.026). Attitude level was high in primary school students compared to intermediate school students (p< 0.001). No significant difference was observed between groups with regard to practice levels (p=0.152). The students exhibited good practice levels, despite fair knowledge and attitude levels.

A Demonstration Sample for Poetry Education: Poem under the Light of "Poetics of the Open Work"

ERIC Educational Resources Information Center

Afacan, Aydin

2016-01-01

The aim of this study is to provide a demonstration sample for the high school stage under the light of "Poetics of the Open Work" that is considered as a step towards comprehending the qualified poem. In this study, has been built in single group pretest-posttest design. Independent variables are applied to a randomly selected group to…

Factors Influencing Teachers' Competence in Developing Resilience in Vulnerable Children in Primary Schools in Uasin Gishu County, Kenya

ERIC Educational Resources Information Center

Silyvier, Tsindoli; Nyandusi, Charles

2015-01-01

The purpose of the study was to assess the effect of teacher characteristics on their competence in developing resilience in vulnerable primary school children. A descriptive survey research design was used. This study was based on resiliency theory as proposed by Krovetz (1998). Simple random sampling was used to select a sample size of 108…

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…

Selection of Common Items as an Unrecognized Source of Variability in Test Equating: A Bootstrap Approximation Assuming Random Sampling of Common Items

ERIC Educational Resources Information Center

Michaelides, Michalis P.; Haertel, Edward H.

2014-01-01

The standard error of equating quantifies the variability in the estimation of an equating function. Because common items for deriving equated scores are treated as fixed, the only source of variability typically considered arises from the estimation of common-item parameters from responses of samples of examinees. Use of alternative, equally…

Lecturers and Postgraduates Perception of Libraries as Promoters of Teaching, Learning, and Research at the University of Ibadan, Nigeria

ERIC Educational Resources Information Center

Oyewole, Olawale; Adetimirin, Airen

2015-01-01

Lecturers and postgraduates are among the users of the university libraries and their perception of the libraries has influence on utilization of the information resources, hence the need for this study. Survey method was adopted for the study and simple random sampling method was used to select sample size of 38 lecturers and 233 postgraduates.…

Santa Clara County Survey of Drug, Alcohol, and Tobacco Use among Students in Grades 5, 7, 9, 11.

ERIC Educational Resources Information Center

Constantine, Norm; And Others

This report presents findings from the Santa Clara County (California) survey of Drug, Alcohol, and Tobacco Use among Students in Grades 5, 7, 9, and 11 administered during the spring of 1991 to 5,180 students in 51 randomly selected county schools. An executive summary discusses sampling error, sample demographics, and findings on drug use…

FROM THE MOUNTAINS TO THE SEA: THE STATE OF MARYLAND'S FRESHWATER STREAMS

EPA Science Inventory

The Maryland Biological Stream Survey, conducted by the Maryland Department of Natural Resources, sampled about 1,000 randomly-selected sites on first through third order freshwater streams throughout Maryland from 1995 to 1997. Biota (fish, benthic macroinvertebrates, herpetofau...

PRELIMINARY REPORT ON NATIONWIDE STUDY OF DRINKING WATER AND CARDIOVASCULAR DISEASES

EPA Science Inventory

This study was designed to further investigate the association(s) of cardiovascular diseases and drinking water constituents. A sample of 4200 adults were randomly selected from 35 geographic areas to represent the civilian noninstitutionalized population of the contiguous United...

A comparison of drug use in driver fatalities and similarly exposed drivers

DOT National Transportation Integrated Search

1977-07-01

Author's abstract: Crash information, urine, blood and bile samples from 900 fatally injured drivers were collected by medical examiners in 22 areas of the country. Randomly selected living drivers were interviewed at times and places of recent fatal...

1998 motor vehicle occupant safety survey. Volume 1, methodology report

DOT National Transportation Integrated Search

2000-03-01

This is the Methodology Report for the 1998 Motor Vehicle Occupant Safety Survey. The survey is conducted on a biennial basis (initiated in 1994), and is administered by telephone to a randomly selected national sample. Two questionnaires are used, e...

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.

Sediment toxicity in mid-continent great rivers (USA)

EPA Science Inventory

In this study, 530 sediment samples were collected from 447 sites between 2004 and 2006 at randomly selected shoreline sites along the main channel of the Ohio, Missouri and Upper Mississippi Rivers as part of the Environmental Monitoring and Assessment Program for Great Rivers E...

TOWARDS USING STABLE SPERMATOZOAL RNAS FOR PROGNOSTIC ASSESSMENT OF MALE FACTOR FERTILITY

EPA Science Inventory

Objective: To establish the stability of spermatozoal RNAs as a means to validate their use as a male fertility marker. Design: Semen samples were randomly selected for 1 of 3 cryopreservation treatments. Setting: An academic research environment. Patient(s): Men aged...

American Healthy Homes Survey: A National Study of Residential Pesticides Measured from Floor Wipes.

EPA Science Inventory

The U.S. Department of Housing and Urban Development in collaboration with the United States Environmental Protection Agency conducted a survey measuring lead, allergens, and insecticides in a randomly selected nationally representative sample of resodential homes. Multistage sa...

Determining Consumer Preference for Furniture Product Characteristics

ERIC Educational Resources Information Center

Turner, Carolyn S.; Edwards, Kay P.

1974-01-01

The paper describes instruments for determining preferences of consumers for selected product characteristics associated with furniture choices--specifically style, color, color scheme, texture, and materials--and the procedures for administration of those instruments. Results are based on a random sampling of public housing residents. (Author/MW)

A sampling strategy to estimate the area and perimeter of irregularly shaped planar regions

Treesearch

Timothy G. Gregoire; Harry T. Valentine

1995-01-01

The length of a randomly oriented ray emanating from an interior point of a planar region can be used to unbiasedly estimate the region's area and perimeter. Estimators and corresponding variance estimators under various selection strategies are presented.

Identification of Teaching Behaviors Which Predict Success for Mainstreamed Students.

ERIC Educational Resources Information Center

Larrivee, Barbara; Algina, James

The final phase of a study investigating effective teaching behaviors for mainstreamed students involved 118 elementary teachers. Teachers provided information on mainstreamed students and a sample of students was randomly selected to represent classification categories (learning disabilities, behavior disorders, speech impairments, and hearing…

Overlooked Threats to Respondent Driven Sampling Estimators: Peer Recruitment Reality, Degree Measures, and Random Selection Assumption.

PubMed

Li, Jianghong; Valente, Thomas W; Shin, Hee-Sung; Weeks, Margaret; Zelenev, Alexei; Moothi, Gayatri; Mosher, Heather; Heimer, Robert; Robles, Eduardo; Palmer, Greg; Obidoa, Chinekwu

2017-06-28

Intensive sociometric network data were collected from a typical respondent driven sample (RDS) of 528 people who inject drugs residing in Hartford, Connecticut in 2012-2013. This rich dataset enabled us to analyze a large number of unobserved network nodes and ties for the purpose of assessing common assumptions underlying RDS estimators. Results show that several assumptions central to RDS estimators, such as random selection, enrollment probability proportional to degree, and recruitment occurring over recruiter's network ties, were violated. These problems stem from an overly simplistic conceptualization of peer recruitment processes and dynamics. We found nearly half of participants were recruited via coupon redistribution on the street. Non-uniform patterns occurred in multiple recruitment stages related to both recruiter behavior (choosing and reaching alters, passing coupons, etc.) and recruit behavior (accepting/rejecting coupons, failing to enter study, passing coupons to others). Some factors associated with these patterns were also associated with HIV risk.

Random Evolutionary Dynamics Driven by Fitness and House-of-Cards Mutations: Sampling Formulae

NASA Astrophysics Data System (ADS)

Huillet, Thierry E.

2017-07-01

We first revisit the multi-allelic mutation-fitness balance problem, especially when mutations obey a house of cards condition, where the discrete-time deterministic evolutionary dynamics of the allelic frequencies derives from a Shahshahani potential. We then consider multi-allelic Wright-Fisher stochastic models whose deviation to neutrality is from the Shahshahani mutation/selection potential. We next focus on the weak selection, weak mutation cases and, making use of a Gamma calculus, we compute the normalizing partition functions of the invariant probability densities appearing in their Wright-Fisher diffusive approximations. Using these results, generalized Ewens sampling formulae (ESF) from the equilibrium distributions are derived. We start treating the ESF in the mixed mutation/selection potential case and then we restrict ourselves to the ESF in the simpler house-of-cards mutations only situation. We also address some issues concerning sampling problems from infinitely-many alleles weak limits.

Identification and selection of cases and controls in the Pneumonia Etiology Research for Child Health project.

PubMed

Deloria-Knoll, Maria; Feikin, Daniel R; Scott, J Anthony G; O'Brien, Katherine L; DeLuca, Andrea N; Driscoll, Amanda J; Levine, Orin S

2012-04-01

Methods for the identification and selection of patients (cases) with severe or very severe pneumonia and controls for the Pneumonia Etiology Research for Child Health (PERCH) project were needed. Issues considered include eligibility criteria and sampling strategies, whether to enroll hospital or community controls, whether to exclude controls with upper respiratory tract infection (URTI) or nonsevere pneumonia, and matching criteria, among others. PERCH ultimately decided to enroll community controls and an additional human immunodeficiency virus (HIV)-infected control group at high HIV-prevalence sites matched on age and enrollment date of cases; controls with symptoms of URTI or nonsevere pneumonia will not be excluded. Systematic sampling of cases (when necessary) and random sampling of controls will be implemented. For each issue, we present the options that were considered, the advantages and disadvantages of each, the rationale for the methods selected for PERCH, and remaining implications and limitations.

Comparative study of feature selection with ensemble learning using SOM variants

NASA Astrophysics Data System (ADS)

Filali, Ameni; Jlassi, Chiraz; Arous, Najet

2017-03-01

Ensemble learning has succeeded in the growth of stability and clustering accuracy, but their runtime prohibits them from scaling up to real-world applications. This study deals the problem of selecting a subset of the most pertinent features for every cluster from a dataset. The proposed method is another extension of the Random Forests approach using self-organizing maps (SOM) variants to unlabeled data that estimates the out-of-bag feature importance from a set of partitions. Every partition is created using a various bootstrap sample and a random subset of the features. Then, we show that the process internal estimates are used to measure variable pertinence in Random Forests are also applicable to feature selection in unsupervised learning. This approach aims to the dimensionality reduction, visualization and cluster characterization at the same time. Hence, we provide empirical results on nineteen benchmark data sets indicating that RFS can lead to significant improvement in terms of clustering accuracy, over several state-of-the-art unsupervised methods, with a very limited subset of features. The approach proves promise to treat with very broad domains.

Silicon solar cell process development, fabrication and analysis

NASA Technical Reports Server (NTRS)

Iles, P. A.; Leung, D. C.

1982-01-01

For UCP Si, randomly selected wafers and wafers cut from two specific ingots were studied. For the randomly selected wafers, a moderate gettering diffusion had little effect. Moreover, an efficiency up to 14% AMI was achieved with advanced processes. For the two specific UCP ingots, ingot #5848-13C displayed severe impurity effects as shown by lower 3sc in the middle of the ingot and low CFF in the top of the ingot. Also the middle portions of this ingot responded to a series of progressively more severe gettering diffusion. Unexplained was the fact that severely gettered samples of this ingot displayed a negative light biased effect on the minority carrier diffusion length while the nongettered or moderately gettered ones had the more conventional positive light biased effect on diffusion length. On the other hand, ingot C-4-21A did not have the problem of ingot 5848-13C and behaved like to the randomly selected wafers. The top half of the ingot was shown to be slightly superior to the bottom half, but moderate gettering helped to narrow the gap.

Phenotypic constraints promote latent versatility and carbon efficiency in metabolic networks.

PubMed

Bardoscia, Marco; Marsili, Matteo; Samal, Areejit

2015-07-01

System-level properties of metabolic networks may be the direct product of natural selection or arise as a by-product of selection on other properties. Here we study the effect of direct selective pressure for growth or viability in particular environments on two properties of metabolic networks: latent versatility to function in additional environments and carbon usage efficiency. Using a Markov chain Monte Carlo (MCMC) sampling based on flux balance analysis (FBA), we sample from a known biochemical universe random viable metabolic networks that differ in the number of directly constrained environments. We find that the latent versatility of sampled metabolic networks increases with the number of directly constrained environments and with the size of the networks. We then show that the average carbon wastage of sampled metabolic networks across the constrained environments decreases with the number of directly constrained environments and with the size of the networks. Our work expands the growing body of evidence about nonadaptive origins of key functional properties of biological networks.

Systematic Evaluation of the Dependence of Deoxyribozyme Catalysis on Random Region Length

PubMed Central

Velez, Tania E.; Singh, Jaydeep; Xiao, Ying; Allen, Emily C.; Wong, On Yi; Chandra, Madhavaiah; Kwon, Sarah C.; Silverman, Scott K.

2012-01-01

Functional nucleic acids are DNA and RNA aptamers that bind targets, or they are deoxyribozymes and ribozymes that have catalytic activity. These functional DNA and RNA sequences can be identified from random-sequence pools by in vitro selection, which requires choosing the length of the random region. Shorter random regions allow more complete coverage of sequence space but may not permit the structural complexity necessary for binding or catalysis. In contrast, longer random regions are sampled incompletely but may allow adoption of more complicated structures that enable function. In this study, we systematically examined random region length (N20 through N60) for two particular deoxyribozyme catalytic activities, DNA cleavage and tyrosine-RNA nucleopeptide linkage formation. For both activities, we previously identified deoxyribozymes using only N40 regions. In the case of DNA cleavage, here we found that shorter N20 and N30 regions allowed robust catalytic function, either by DNA hydrolysis or by DNA deglycosylation and strand scission via β-elimination, whereas longer N50 and N60 regions did not lead to catalytically active DNA sequences. Follow-up selections with N20, N30, and N40 regions revealed an interesting interplay of metal ion cofactors and random region length. Separately, for Tyr-RNA linkage formation, N30 and N60 regions provided catalytically active sequences, whereas N20 was unsuccessful, and the N40 deoxyribozymes were functionally superior (in terms of rate and yield) to N30 and N60. Collectively, the results indicate that with future in vitro selection experiments for DNA and RNA catalysts, and by extension for aptamers, random region length should be an important experimental variable. PMID:23088677

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

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.

PubMed Central

King-Shier, Kathryn M; Hemmelgarn, Brenda R; Musto, Richard; Quan, Hude

2014-01-01

Background: Francophones who live outside the primarily French-speaking province of Quebec, Canada, risk being excluded from research by lack of a sampling frame. We examined the adequacy of random sampling, advertising, and respondent-driven sampling for recruitment of francophones for survey research. Methods: We recruited francophones residing in the city of Calgary, Alberta, through advertising and respondentdriven sampling. These 2 samples were then compared with a random subsample of Calgary francophones derived from the 2006 Canadian Community Health Survey (CCHS). We assessed the effectiveness of advertising and respondent-driven sampling in relation to the CCHS sample by comparing demographic characteristics and selected items from the CCHS (specifically self-reported general health status, perceived weight, and having a family doctor). Results: We recruited 120 francophones through advertising and 145 through respondent-driven sampling; the random sample from the CCHS consisted of 259 records. The samples derived from advertising and respondentdriven sampling differed from the CCHS in terms of age (mean ages 41.0, 37.6, and 42.5 years, respectively), sex (proportion of males 26.1%, 40.6%, and 56.6%, respectively), education (college or higher 86.7% , 77.9% , and 59.1%, respectively), place of birth (immigrants accounting for 45.8%, 55.2%, and 3.7%, respectively), and not having a regular medical doctor (16.7%, 34.5%, and 16.6%, respectively). Differences were not tested statistically because of limitations on the analysis of CCHS data imposed by Statistics Canada. Interpretation: The samples generated exclusively through advertising and respondent-driven sampling were not representative of the gold standard sample from the CCHS. Use of such biased samples for research studies could generate misleading results. PMID:25426180

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.

The Level of High-Order Thinking and Its Relation to Quality of Life among Students at Ajloun University College

ERIC Educational Resources Information Center

Al Rabadi, Wail Minwer; Salem, Rifqa Khleif

2018-01-01

The study was designed to identify the effect of high-order thinking on the quality of life among Ajloun University students. The study used the associative method. The randomly selected sample consisted of 147 students from Ajloun University College. The study used two tools: The two measures were applied to the sample of the current study after…

The Effect Of Age At Harvest On Bending And Tensile Properties Of Loblolly Pine From The Coastal Plain

Treesearch

Robert H. McAlister; Alexander Clark; Joseph R. Saucier

1997-01-01

The effect of rotation age on strength and stiffness of lumber produced from unthinned loblolly pine stands in the Coastal Plain of Georgia was examined. Six stands representing 22-, 28-, and 40-year-old roations were sampled. A stratified random sample of trees 8 to 16 inches in diameter at breast height was selected from each stand and processed into lumber....

The Integration of International Agricultural Concepts into Agricultural Science Programs in the North Central Region of the United States. Summary of Research 78.

ERIC Educational Resources Information Center

Ibezim, Don O.; McCracken, J. David

A study examined the extent to which international agricultural dimensions were taught in secondary agricultural programs and factors associated with the extent of integration. A systematic sampling technique was used to select a random sample of 332 of the 2,612 secondary agricultural teachers in 12 states of the North Central United States. Of…

The Effect of Using Computer Games in Teaching Mathematics on Developing the Number Sense of Fourth Grade Students

ERIC Educational Resources Information Center

Nejem, Khamis Mousa; Muhanna, Wafa

2013-01-01

The purpose of this study was to investigate the effect of using computer games in teaching mathematics on developing the number sense of fourth grade students. To achieve this purpose a study sample of (81) students was selected from the fourth grade. This sample was divided into two groups. One group was randomly chosen to be the experimental…

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.

Impact assessment and decontamination of pesticides from meat under different culinary processes.

PubMed

Sengupta, Dwaipayan; Aktar, Md Wasim; Alam, Samsul; Chowdhury, Ashim

2010-10-01

A total of 75 animals between 1.5 and 8 years old were randomly selected for the study. Of these, 57.8% were cross-bred animals and the rest were non-descript. Moreover, 61.8% of the animals under study were brought for slaughter from local sources and the rest from farm houses. Samples collected from five districts revealed contamination with traces of organochlorine pesticides (0.01-0.22 microg g(-1)) and organophosphorus pesticides (0.111-0.098 microg g(-1)). In general, all the raw meat samples possessed dichlorodiphenyltrichloroethane at the highest level. Contamination was highest in cow meat samples and lowest in chicken samples. No particular district-wise trend was obtained for the pesticides selected for analysis. Subsequent decontamination study revealed that cooking is the best option in reducing pesticide load in raw meat samples. Cooked chicken is the safest foodstuff for consumption.

Robust online tracking via adaptive samples selection with saliency detection

NASA Astrophysics Data System (ADS)

Yan, Jia; Chen, Xi; Zhu, QiuPing

2013-12-01

Online tracking has shown to be successful in tracking of previously unknown objects. However, there are two important factors which lead to drift problem of online tracking, the one is how to select the exact labeled samples even when the target locations are inaccurate, and the other is how to handle the confusors which have similar features with the target. In this article, we propose a robust online tracking algorithm with adaptive samples selection based on saliency detection to overcome the drift problem. To deal with the problem of degrading the classifiers using mis-aligned samples, we introduce the saliency detection method to our tracking problem. Saliency maps and the strong classifiers are combined to extract the most correct positive samples. Our approach employs a simple yet saliency detection algorithm based on image spectral residual analysis. Furthermore, instead of using the random patches as the negative samples, we propose a reasonable selection criterion, in which both the saliency confidence and similarity are considered with the benefits that confusors in the surrounding background are incorporated into the classifiers update process before the drift occurs. The tracking task is formulated as a binary classification via online boosting framework. Experiment results in several challenging video sequences demonstrate the accuracy and stability of our tracker.

Honest Importance Sampling with Multiple Markov Chains

PubMed Central

Tan, Aixin; Doss, Hani; Hobert, James P.

2017-01-01

Importance sampling is a classical Monte Carlo technique in which a random sample from one probability density, π1, is used to estimate an expectation with respect to another, π. The importance sampling estimator is strongly consistent and, as long as two simple moment conditions are satisfied, it obeys a central limit theorem (CLT). Moreover, there is a simple consistent estimator for the asymptotic variance in the CLT, which makes for routine computation of standard errors. Importance sampling can also be used in the Markov chain Monte Carlo (MCMC) context. Indeed, if the random sample from π1 is replaced by a Harris ergodic Markov chain with invariant density π1, then the resulting estimator remains strongly consistent. There is a price to be paid however, as the computation of standard errors becomes more complicated. First, the two simple moment conditions that guarantee a CLT in the iid case are not enough in the MCMC context. Second, even when a CLT does hold, the asymptotic variance has a complex form and is difficult to estimate consistently. In this paper, we explain how to use regenerative simulation to overcome these problems. Actually, we consider a more general set up, where we assume that Markov chain samples from several probability densities, π1, …, πk, are available. We construct multiple-chain importance sampling estimators for which we obtain a CLT based on regeneration. We show that if the Markov chains converge to their respective target distributions at a geometric rate, then under moment conditions similar to those required in the iid case, the MCMC-based importance sampling estimator obeys a CLT. Furthermore, because the CLT is based on a regenerative process, there is a simple consistent estimator of the asymptotic variance. We illustrate the method with two applications in Bayesian sensitivity analysis. The first concerns one-way random effects models under different priors. The second involves Bayesian variable selection in linear regression, and for this application, importance sampling based on multiple chains enables an empirical Bayes approach to variable selection. PMID:28701855

Honest Importance Sampling with Multiple Markov Chains.

PubMed

Tan, Aixin; Doss, Hani; Hobert, James P

2015-01-01

Importance sampling is a classical Monte Carlo technique in which a random sample from one probability density, π 1 , is used to estimate an expectation with respect to another, π . The importance sampling estimator is strongly consistent and, as long as two simple moment conditions are satisfied, it obeys a central limit theorem (CLT). Moreover, there is a simple consistent estimator for the asymptotic variance in the CLT, which makes for routine computation of standard errors. Importance sampling can also be used in the Markov chain Monte Carlo (MCMC) context. Indeed, if the random sample from π 1 is replaced by a Harris ergodic Markov chain with invariant density π 1 , then the resulting estimator remains strongly consistent. There is a price to be paid however, as the computation of standard errors becomes more complicated. First, the two simple moment conditions that guarantee a CLT in the iid case are not enough in the MCMC context. Second, even when a CLT does hold, the asymptotic variance has a complex form and is difficult to estimate consistently. In this paper, we explain how to use regenerative simulation to overcome these problems. Actually, we consider a more general set up, where we assume that Markov chain samples from several probability densities, π 1 , …, π k , are available. We construct multiple-chain importance sampling estimators for which we obtain a CLT based on regeneration. We show that if the Markov chains converge to their respective target distributions at a geometric rate, then under moment conditions similar to those required in the iid case, the MCMC-based importance sampling estimator obeys a CLT. Furthermore, because the CLT is based on a regenerative process, there is a simple consistent estimator of the asymptotic variance. We illustrate the method with two applications in Bayesian sensitivity analysis. The first concerns one-way random effects models under different priors. The second involves Bayesian variable selection in linear regression, and for this application, importance sampling based on multiple chains enables an empirical Bayes approach to variable selection.

10 CFR 431.383 - Enforcement process for electric motors.

Code of Federal Regulations, 2014 CFR

2014-01-01

... general purpose electric motor of equivalent electrical design and enclosure rather than replacing the... equivalent electrical design and enclosure rather than machining and attaching an endshield. ... sample of up to 20 units will then be randomly selected from one or more subdivided groups within the...

Why Students Are Hostile to Free Enterprise

ERIC Educational Resources Information Center

Kilpatrick, James L.

1975-01-01

A Gallup study is described, which was commissioned by Oklahoma State Christian College regarding the philosophical orientation of college students generally (liberal or conservative). The author presents selected findings and concludes that students in the national random sample are ignorant of industrial life and generally hostile toward the…

American Healthy Homes Survey: A National Study of Residential Phthalates Measured from Floor Wipes

EPA Science Inventory

The United States Environmental Protection Agency (U.S. EPA), in collaboration with the U.S. Department of Housing and Urban Development (HUD), conducted a survey measuring phthalates in randomly selected residential homes throughout the U.S. Multistage sampling with clustering w...

DISTRIBUTIONS OF LAKE FISHES OF THE NORTHEAST USA--III. SALMONIDAE AND ASSOCIATED COLDWATER SPECIES

EPA Science Inventory

We present distributional maps and discuss native status for fish species characteristic of coldwater lakes, sampled from 203 randomly selected lakes in the northeastern USA (New England, New York, New Jersey). Eleven coldwater fish species from four families (Salmonidae, Osmeri...

Multi-Sensory Intervention Observational Research

ERIC Educational Resources Information Center

Thompson, Carla J.

2011-01-01

An observational research study based on sensory integration theory was conducted to examine the observed impact of student selected multi-sensory experiences within a multi-sensory intervention center relative to the sustained focus levels of students with special needs. A stratified random sample of 50 students with severe developmental…

PERSONAL VALUES, BELIEFS, AND ECOLOGICAL RISK PERCEPTION

EPA Science Inventory

A mail survey on ecological risk perception was administered in the summer of 2002 to a randomized sample of the lay public and to selected risk professionals at the U.S. Environmental Protection Agency (US EPA). The ranking of 24 ecological risk items, from global climate change...

Enhancing Employee Skills.

ERIC Educational Resources Information Center

1999

This document contains four symposium papers on enhancing employee skills. "The Effect of Study Skills Training Intervention on United States Air Force Aeromedical Apprentices" (John C. Griffith) demonstrates how study skills intervention resulted in a significant increase in the end-of-course scores of a sample of 90 randomly selected Air Force…

Treatment selection in a randomized clinical trial via covariate-specific treatment effect curves.

PubMed

Ma, Yunbei; Zhou, Xiao-Hua

2017-02-01

For time-to-event data in a randomized clinical trial, we proposed two new methods for selecting an optimal treatment for a patient based on the covariate-specific treatment effect curve, which is used to represent the clinical utility of a predictive biomarker. To select an optimal treatment for a patient with a specific biomarker value, we proposed pointwise confidence intervals for each covariate-specific treatment effect curve and the difference between covariate-specific treatment effect curves of two treatments. Furthermore, to select an optimal treatment for a future biomarker-defined subpopulation of patients, we proposed confidence bands for each covariate-specific treatment effect curve and the difference between each pair of covariate-specific treatment effect curve over a fixed interval of biomarker values. We constructed the confidence bands based on a resampling technique. We also conducted simulation studies to evaluate finite-sample properties of the proposed estimation methods. Finally, we illustrated the application of the proposed method in a real-world data set.

The quality of reporting of randomized controlled trials of traditional Chinese medicine: a survey of 13 randomly selected journals from mainland China.

PubMed

Wang, Gang; Mao, Bing; Xiong, Ze-Yu; Fan, Tao; Chen, Xiao-Dong; Wang, Lei; Liu, Guan-Jian; Liu, Jia; Guo, Jia; Chang, Jing; Wu, Tai-Xiang; Li, Ting-Qian

2007-07-01

The number of randomized controlled trials (RCTs) of traditional Chinese medicine (TCM) is increasing. However, there have been few systematic assessments of the quality of reporting of these trials. This study was undertaken to evaluate the quality of reporting of RCTs in TCM journals published in mainland China from 1999 to 2004. Thirteen TCM journals were randomly selected by stratified sampling of the approximately 100 TCM journals published in mainland China. All issues of the selected journals published from 1999 to 2004 were hand-searched according to guidelines from the Cochrane Centre. All reviewers underwent training in the evaluation of RCTs at the Chinese Centre of Evidence-based Medicine. A comprehensive quality assessment of each RCT was completed using a modified version of the Consolidated Standards of Reporting Trials (CONSORT) checklist (total of 30 items) and the Jadad scale. Disagreements were resolved by consensus. Seven thousand four hundred twenty-two RCTs were identified. The proportion of published RCTs relative to all types of published clinical trials increased significantly over the period studied, from 18.6% in 1999 to 35.9% in 2004 (P < 0.001). The mean (SD) Jadad score was 1.03 (0.61) overall. One RCT had a Jadad score of 5 points; 14 had a score of 4 points; and 102 had a score of 3 points. The mean (SD) Jadad score was 0.85 (0.53) in 1999 (746 RCTs) and 1.20 (0.62) in 2004 (1634 RCTs). Across all trials, 39.4% of the items on the modified CONSORT checklist were reported, which was equivalent to 11.82 (5.78) of the 30 items. Some important methodologic components of RCTs were incompletely reported, such as sample-size calculation (reported in 1.1% of RCTs), randomization sequence (7.9%), allocation concealment (0.3 %), implementation of the random-allocation sequence (0%), and analysis of intention to treat (0%). The findings of this study indicate that the quality of reporting of RCTs of TCM has improved, but remains poor.

The signature of positive selection at randomly chosen loci.

PubMed

Przeworski, Molly

2002-03-01

In Drosophila and humans, there are accumulating examples of loci with a significant excess of high-frequency-derived alleles or high levels of linkage disequilibrium, relative to a neutral model of a random-mating population of constant size. These are features expected after a recent selective sweep. Their prevalence suggests that positive directional selection may be widespread in both species. However, as I show here, these features do not persist long after the sweep ends: The high-frequency alleles drift to fixation and no longer contribute to polymorphism, while linkage disequilibrium is broken down by recombination. As a result, loci chosen without independent evidence of recent selection are not expected to exhibit either of these features, even if they have been affected by numerous sweeps in their genealogical history. How then can we explain the patterns in the data? One possibility is population structure, with unequal sampling from different subpopulations. Alternatively, positive selection may not operate as is commonly modeled. In particular, the rate of fixation of advantageous mutations may have increased in the recent past.

Comparison of sampling methods for hard-to-reach francophone populations: yield and adequacy of advertisement and respondent-driven sampling.

PubMed

Ngwakongnwi, Emmanuel; King-Shier, Kathryn M; Hemmelgarn, Brenda R; Musto, Richard; Quan, Hude

2014-01-01

Francophones who live outside the primarily French-speaking province of Quebec, Canada, risk being excluded from research by lack of a sampling frame. We examined the adequacy of random sampling, advertising, and respondent-driven sampling for recruitment of francophones for survey research. We recruited francophones residing in the city of Calgary, Alberta, through advertising and respondentdriven sampling. These 2 samples were then compared with a random subsample of Calgary francophones derived from the 2006 Canadian Community Health Survey (CCHS). We assessed the effectiveness of advertising and respondent-driven sampling in relation to the CCHS sample by comparing demographic characteristics and selected items from the CCHS (specifically self-reported general health status, perceived weight, and having a family doctor). We recruited 120 francophones through advertising and 145 through respondent-driven sampling; the random sample from the CCHS consisted of 259 records. The samples derived from advertising and respondentdriven sampling differed from the CCHS in terms of age (mean ages 41.0, 37.6, and 42.5 years, respectively), sex (proportion of males 26.1%, 40.6%, and 56.6%, respectively), education (college or higher 86.7% , 77.9% , and 59.1%, respectively), place of birth (immigrants accounting for 45.8%, 55.2%, and 3.7%, respectively), and not having a regular medical doctor (16.7%, 34.5%, and 16.6%, respectively). Differences were not tested statistically because of limitations on the analysis of CCHS data imposed by Statistics Canada. The samples generated exclusively through advertising and respondent-driven sampling were not representative of the gold standard sample from the CCHS. Use of such biased samples for research studies could generate misleading results.

Assessing the quality of reproductive health services in Egypt via exit interviews.

PubMed

Zaky, Hassan H M; Khattab, Hind A S; Galal, Dina

2007-05-01

This study assesses the quality of reproductive health services using client satisfaction exit interviews among three groups of primary health care units run by the Ministry of Health and Population of Egypt. Each group applied a different model of intervention. The Ministry will use the results in assessing its reproductive health component in the health sector reform program, and benefits from the strengths of other models of intervention. The sample was selected in two stages. First, a stratified random sampling procedure was used to select the health units. Then the sample of female clients in each health unit was selected using the systematic random approach, whereby one in every two women visiting the unit was approached. All women in the sample coming for reproductive health services were included in the analysis. The results showed that reproductive health beneficiaries at the units implementing the new health sector reform program were more satisfied with the quality of services. Still there were various areas where clients showed significant dissatisfaction, such as waiting time, interior furnishings, cleanliness of the units and consultation time. The study showed that the staff of these units did not provide a conductive social environment as other interventions did. A significant proportion of women expressed their intention to go to private physicians owing to their flexible working hours and variety specializations. Beneficiaries were generally more satisfied with the quality of health services after attending the reformed units than the other types of units, but the generalization did not fully apply. Areas of weakness are identified.

Kindergarten Teachers' Experience with Reporting Child Abuse in Taiwan

ERIC Educational Resources Information Center

Feng, Jui-Ying; Huang, Tzu-Yi; Wang, Chi-Jen

2010-01-01

Objective: The objectives were to examine factors associated with reporting child abuse among kindergarten teachers in Taiwan based on the Theory of Planned Behavior (TPB). Method: A stratified quota sampling technique was used to randomly select kindergarten teachers in Taiwan. The Child Abuse Intention Report Scale, which includes demographics,…

Anti-Depressants, Suicide, and Drug Regulation

ERIC Educational Resources Information Center

Ludwig, Jens; Marcotte, Dave E.

2005-01-01

Policymakers are increasingly concerned that a relatively new class of anti-depressant drugs, selective serotonin re-uptake inhibitors (SSRI), may increase the risk of suicide for at least some patients, particularly children. Prior randomized trials are not informative on this question because of small sample sizes and other limitations. Using…

Assessing Postgraduate Students' Critical Thinking Ability

ERIC Educational Resources Information Center

Javed, Muhammad; Nawaz, Muhammad Atif; Qurat-Ul-Ain, Ansa

2015-01-01

This paper addresses to assess the critical thinking ability of postgraduate students. The target population was the male and female students at University level in Pakistan. A small sample of 45 male and 45 female students were selected randomly from The Islamia University of Bahawalpur, Pakistan. Cornell Critical Thinking Test Series, The…

75 FR 43172 - Maternal, Infant, and Early Childhood Home Visiting Program

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-23

... the evaluation results have been published in a peer-reviewed journal; or (bb) quasi-experimental... design (i.e. randomized controlled trial [RCT] or quasi-experimental design [QED]), level of attrition... a quasi-experimental design as a study design in which sample members are selected for the program...

College Counselors' Perceptions and Practices regarding Anticipatory Guidance on Firearms

ERIC Educational Resources Information Center

Price, James; Mrdjenovich, Adam J.; Thompson, Amy; Dake, Joseph A.

2009-01-01

Objectives: This study assessed college counselors' anticipatory guidance on firearms for student clients. Participants: The membership of the Association for University and College Counseling Center Directors was used to identify a national random sample of counseling centers (n = 361). One counselor from each center was selected to survey.…

Science Laboratory Environment and Academic Performance

ERIC Educational Resources Information Center

Aladejana, Francisca; Aderibigbe, Oluyemisi

2007-01-01

The study determined how students assess the various components of their science laboratory environment. It also identified how the laboratory environment affects students' learning outcomes. The modified ex-post facto design was used. A sample of 328 randomly selected students was taken from a population of all Senior Secondary School chemistry…

Collective Negotiations and Teacher Satisfaction in Selected Indiana Secondary Schools.

ERIC Educational Resources Information Center

Davies, Paul R.; Kline, Charles E.

This paper reports a study that sought to determine whether differences in bargaining procedures are related to differences in teacher satisfaction or morale. Of the forty schools in the random sample, 27 were operating under traditional collective negotiation procedures -- teachers relatively unorganized; eight were operating under procedural…

Psychological Distress and Related Factors in Female College Students

ERIC Educational Resources Information Center

Vazquez, Fernando L.; Otero, Patricia; Diaz, Olga

2012-01-01

Objective: This study assessed the psychological distress in Spanish college women and analyzed it in relation to sociodemographic and academic factors. Participants and Methods: The authors selected a stratified random sampling of 1,043 college women (average age of 22.2 years). Sociodemographic and academic information were collected, and…

ALIEN SPECIES IMPORTANTANCE IN NATIVE VEGETATION ALONG WADEABLE STREAMS, JOHN DAY RIVER BASIN, OREGON, USA

EPA Science Inventory

We evaluated the importance of alien species in existing vegetation along wadeable streams of a large, topographically diverse river basin in eastern Oregon, USA; sampling 165 plots (30 × 30 m) across 29 randomly selected 1-km stream reaches. Plots represented eight streamside co...

Psycholinguistic Behaviors of Black, Disadvantaged Rural Children.

ERIC Educational Resources Information Center

Cowles, Milly; Daniel, Kathryn Barchard

This study was designed to compare the psycholinguistic abilities of a randomly selected sample of 32 kindergarten children and 32 first grade children (with no kindergarten experience) and to analyze any discrepancy existing between psycholinguistic age (PLA) and chronological age (CA). Each of the kindergarten classrooms from which children were…

Examinations of Home Economics Textbooks for Sex Bias.

ERIC Educational Resources Information Center

Weis, Susan F.

1979-01-01

Four analyses were conducted on a sample of 100 randomly selected, secondary home economics textbooks published between 1964 and 1974. Results indicated that the contents presented sex bias in language usage, in pictures portraying male and female role environments, and in role behaviors and expectations emphasized. (Author/JH)

Autism Developmental Profiles and Cooperation with Oral Health Screening

ERIC Educational Resources Information Center

Du, Rennan Y.; Yiu, Cynthia C. Y.; Wong, Virginia C. N.; McGrath, Colman P.

2015-01-01

To determine the associations between autism developmental profiles and cooperation with an oral health screening among preschool children with autism spectrum disorders (ASDs). A random sample of Special Child Care Centres registered with the Government Social Welfare Department in Hong Kong was selected (19 out of 37 Centres). All preschool…

Women in University Management: The Nigerian Experience

ERIC Educational Resources Information Center

Abiodun-Oyebanji, Olayemi; Olaleye, F.

2011-01-01

This study examined women in university management in Nigeria. It was a descriptive research of the survey type. The population of the study comprised all the public universities in southwest Nigeria, out of which three were selected through the stratified random sampling technique. Three hundred respondents who were in management positions were…

Negative Particles and Morphemes in Jordanian Arabic Dialects

ERIC Educational Resources Information Center

Mrayat, Ahmad

2015-01-01

This paper aims at investigating the negative particles and morphemes in three main Jordanian dialects (Urban, Rural and Bedouin). This quantitative and qualitative study includes 30 teachers from different disciplines who use these dialects. The sample of the study was selected randomly. The research used two research instruments, a checklist and…

School Psychologist Diagnostic Decision-Making: A Pilot Study

ERIC Educational Resources Information Center

Barnard-Brak, Lucy; Stevens, Tara; Robinson, Eric; Holt, Ann

2013-01-01

The current study examined the diagnostic decision-making of school psychologists as a function of a student's disability and academic performance with three research questions using a randomly-selected sample of school psychologists from the state of Texas. Results from the first research question indicated that school psychologists significantly…

The Vocational Personality of School Psychologists in the United States

ERIC Educational Resources Information Center

Toomey, Kristine D.; Levinson, Edward M.; Morrison, Takea J.

2008-01-01

This study represents the first empirical test of the vocational personality of US school psychologists. Specifically, we investigated the personality of school psychologists using Holland's (1997) well-researched theory of vocational personalities and work environments. The sample consisted of 241 randomly selected members of the National…

APPLICATION OF A MULTIPURPOSE UNEQUAL-PROBABILITY STREAM SURVEY IN THE MID-ATLANTIC COASTAL PLAIN

EPA Science Inventory

A stratified random sample with unequal-probability selection was used to design a multipurpose survey of headwater streams in the Mid-Atlantic Coastal Plain. Objectives for data from the survey include unbiased estimates of regional stream conditions, and adequate coverage of un...

Relationship of Study Habits with Mathematics Achievement

ERIC Educational Resources Information Center

Odiri, Onoshakpokaiye E.

2015-01-01

The study examined the relationship of study habits of students and their achievement in mathematics. The method used for the study was correlation design. A sample of 500 students were randomly selected from 25 public secondary schools in Delta Central Senatorial District, Delta State, Nigeria. Questionnaires were drawn to gather data on…

Perceptions of the Performance of Community College Faculty: Dissertation Research Findings.

ERIC Educational Resources Information Center

Vickers, Mozelle Carver

A sample of 30 instructors nominated as effective teachers to the Piper Foundation and 31 randomly selected control instructors from the same 14 Texas colleges were evaluated by students, former students, administrators, peers, and the instructors themselves. The research instrument incorporated ten sets of characteristics expressed as polar…

The Analysis of Iranian Students' Persistence in Online Education

ERIC Educational Resources Information Center

Mahmodi, Mahdi; Ebrahimzade, Issa

2015-01-01

In the following research, the relationship between instructional interaction and student persistence in e-learning has been analyzed. In order to conduct a descriptive-analytic survey, 744 undergraduate e-students were selected by stratified random sampling method to examine not only the frequency and the methods of establishing an instructional…

Exploring the Innovative Personality Characteristics among Teachers

ERIC Educational Resources Information Center

Othman, Nooraini

2016-01-01

The aim of this study is to explore the characteristics of innovative personality among teachers in Malaysia. Samples of the research were randomly selected among secondary school teachers in three districts in Malaysia. Research instrument was self-developed by the researchers based on interviews carried out with some resource persons who are…

The Impact of Electronic Communication Technology on Written Language

ERIC Educational Resources Information Center

Hamzah, Mohd. Sahandri Gani B.; Ghorbani, Mohd. Reza; Abdullah, Saifuddin Kumar B.

2009-01-01

Communication technology is changing things. Language is no exception. Some language researchers argue that language is deteriorating due to increased use in electronic communication. The present paper investigated 100 randomly selected electronic mails (e-mails) and 50 short messaging system (SMS) messages of a representative sample of…

What Factors Predict Student Self-Rated Physical Health?

ERIC Educational Resources Information Center

Vingilis, Evelyn; Wade, Terrance J.; Adlaf, Edward

1998-01-01

Data from a randomly selected sample of 840 Ontario students were used to examine factors that affect self-rated physical health. Analyses focused on demographics, family structure, financial situation, child-parent relationship, school achievement, self-esteem, alcohol, tobacco, and cannabis use as factors which directly and indirectly influence…

Employment of College Students.

ERIC Educational Resources Information Center

High, Robert V.

A survey was conducted to determine the effect on academic performance, if any, of employment on undergraduate college students. A questionnaire was sent to professors at 3 four-year colleges on Long Island (New York); various day classes were randomly selected. The final sample of n=257 represented approximately a 30 percent response. The…

Disengaging from Workplace Relationships. A Research Note

ERIC Educational Resources Information Center

Sias, Patricia M.; Perry, Tara

2004-01-01

A randomly-selected sample of 306 adults employed full-time rated how likely individuals would be to use various communication strategies (cost escalation, depersonalization, and state-of-the-relationship talk) to disengage from a workplace relationship (with the target of the deteriorations being a supervisor, a peer coworker, or a subordinate…

Conducting a wildland visual resources inventory

Treesearch

James F. Palmer

1979-01-01

This paper describes a procedure for systematically inventorying the visual resources of wildland environments. Visual attributes are recorded photographically using two separate sampling methods: one based on professional judgment and the other on random selection. The location and description of each inventoried scene are recorded on U.S. Geological Survey...

Assessing Principals' Quality Assurance Strategies in Osun State Secondary Schools, Nigeria

ERIC Educational Resources Information Center

Fasasi, Yunus Adebunmi; Oyeniran, Saheed

2014-01-01

This paper examined principals' quality assurance strategies in secondary schools in Osun State, Nigeria. The study adopted a descriptive survey research design. Stratified random sampling technique was used to select 10 male and 10 female principals, and 190 male and190 female teachers. "Secondary School Principal Quality Assurance…

The Relationship Between Self Concept and Marital Adjustment.

ERIC Educational Resources Information Center

Hall, William M., Jr.; Valine, Warren J.

The purpose of this study was to investigate the relationship between self concept and marital adjustment for married students and their spouses in a commuter college setting. The sample consisted of a random selection of 50 "both spouses commuting" couples, 50 "husband only commuting" couples, and 50 "wife only…

Some Communication Effects of Charity Advertising Campaigns.

ERIC Educational Resources Information Center

Moore, Roy L.; And Others

A study was conducted to examine the relationship of advertising exposure to a variety of cognitive and affective variables in a nonprofit charity campaign. The study also tested the transactional model of advertising effects, which combines exposure, motivations, and gratifications for viewing. A sample of 350 adults was randomly selected and…

SHRM Work & Family Survey Report, 1992.

ERIC Educational Resources Information Center

Society for Human Resource Management, Alexandria, VA.

In March 1992, a random sample of 5,600 human resource professionals was selected from the membership of the Society for Human Resource Management (SHRM) and surveyed regarding family issues in the workplace. Respondents were asked to provide information on the size and other characteristics of their organization and workplace practices, and were…

The 15-Second Television Commercial: A Study of Executive Perception.

ERIC Educational Resources Information Center

Asahina, Roberta R.

An exploratory study examined the perceptions of creative directors and broadcast production managers in advertising agencies regarding the perceived effects of the 15-second commercial upon creative formats and production techniques. A sample of 600 randomly selected advertising executives and managers were surveyed using a 55-item mailed…

34 CFR 200.89 - MEP allocations; Re-interviewing; Eligibility documentation; and Quality control.

Code of Federal Regulations, 2011 CFR

2011-07-01

... determinations being tested) trained to conduct personal interviews and to understand and apply program... child eligibility determinations through the re-interview of a randomly selected sample of children previously identified as migratory. In conducting these re-interviews, an SEA must— (i) Use, at least once...

34 CFR 200.89 - MEP allocations; Re-interviewing; Eligibility documentation; and Quality control.

Code of Federal Regulations, 2010 CFR

2010-07-01

... determinations being tested) trained to conduct personal interviews and to understand and apply program... child eligibility determinations through the re-interview of a randomly selected sample of children previously identified as migratory. In conducting these re-interviews, an SEA must— (i) Use, at least once...

Physical Education Teachers' Organizational Commitment

ERIC Educational Resources Information Center

Demir, Hayri

2013-01-01

The aim of this study was to determine physical education teachers' organizational commitment levels. The sample consisted of 204 physical education teachers working in the city center of Konya in the 2011 to 2012 academic year. The respondents were randomly selected in this research. Data collected for this research by using the Scale for…

Simulation of 'hitch-hiking' genealogies.

PubMed

Slade, P F

2001-01-01

An ancestral influence graph is derived, an analogue of the coalescent and a composite of Griffiths' (1991) two-locus ancestral graph and Krone and Neuhauser's (1997) ancestral selection graph. This generalizes their use of branching-coalescing random graphs so as to incorporate both selection and recombination into gene genealogies. Qualitative understanding of a 'hitch-hiking' effect on genealogies is pursued via diagrammatic representation of the genealogical process in a two-locus, two-allele haploid model. Extending the simulation technique of Griffiths and Tavare (1996), computational estimation of expected times to the most recent common ancestor of samples of n genes under recombination and selection in two-locus, two-allele haploid and diploid models are presented. Such times are conditional on sample configuration. Monte Carlo simulations show that 'hitch-hiking' is a subtle effect that alters the conditional expected depth of the genealogy at the linked neutral locus depending on a mutation-selection-recombination balance.

A statistical approach to selecting and confirming validation targets in -omics experiments

PubMed Central

2012-01-01

Background Genomic technologies are, by their very nature, designed for hypothesis generation. In some cases, the hypotheses that are generated require that genome scientists confirm findings about specific genes or proteins. But one major advantage of high-throughput technology is that global genetic, genomic, transcriptomic, and proteomic behaviors can be observed. Manual confirmation of every statistically significant genomic result is prohibitively expensive. This has led researchers in genomics to adopt the strategy of confirming only a handful of the most statistically significant results, a small subset chosen for biological interest, or a small random subset. But there is no standard approach for selecting and quantitatively evaluating validation targets. Results Here we present a new statistical method and approach for statistically validating lists of significant results based on confirming only a small random sample. We apply our statistical method to show that the usual practice of confirming only the most statistically significant results does not statistically validate result lists. We analyze an extensively validated RNA-sequencing experiment to show that confirming a random subset can statistically validate entire lists of significant results. Finally, we analyze multiple publicly available microarray experiments to show that statistically validating random samples can both (i) provide evidence to confirm long gene lists and (ii) save thousands of dollars and hundreds of hours of labor over manual validation of each significant result. Conclusions For high-throughput -omics studies, statistical validation is a cost-effective and statistically valid approach to confirming lists of significant results. PMID:22738145

Not accounting for interindividual variability can mask habitat selection patterns: a case study on black bears.

PubMed

Lesmerises, Rémi; St-Laurent, Martin-Hugues

2017-11-01

Habitat selection studies conducted at the population scale commonly aim to describe general patterns that could improve our understanding of the limiting factors in species-habitat relationships. Researchers often consider interindividual variation in selection patterns to control for its effects and avoid pseudoreplication by using mixed-effect models that include individuals as random factors. Here, we highlight common pitfalls and possible misinterpretations of this strategy by describing habitat selection of 21 black bears Ursus americanus. We used Bayesian mixed-effect models and compared results obtained when using random intercept (i.e., population level) versus calculating individual coefficients for each independent variable (i.e., individual level). We then related interindividual variability to individual characteristics (i.e., age, sex, reproductive status, body condition) in a multivariate analysis. The assumption of comparable behavior among individuals was verified only in 40% of the cases in our seasonal best models. Indeed, we found strong and opposite responses among sampled bears and individual coefficients were linked to individual characteristics. For some covariates, contrasted responses canceled each other out at the population level. In other cases, interindividual variability was concealed by the composition of our sample, with the majority of the bears (e.g., old individuals and bears in good physical condition) driving the population response (e.g., selection of young forest cuts). Our results stress the need to consider interindividual variability to avoid misinterpretation and uninformative results, especially for a flexible and opportunistic species. This study helps to identify some ecological drivers of interindividual variability in bear habitat selection patterns.

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.

Estimation of reference intervals from small samples: an example using canine plasma creatinine.

PubMed

Geffré, A; Braun, J P; Trumel, C; Concordet, D

2009-12-01

According to international recommendations, reference intervals should be determined from at least 120 reference individuals, which often are impossible to achieve in veterinary clinical pathology, especially for wild animals. When only a small number of reference subjects is available, the possible bias cannot be known and the normality of the distribution cannot be evaluated. A comparison of reference intervals estimated by different methods could be helpful. The purpose of this study was to compare reference limits determined from a large set of canine plasma creatinine reference values, and large subsets of this data, with estimates obtained from small samples selected randomly. Twenty sets each of 120 and 27 samples were randomly selected from a set of 1439 plasma creatinine results obtained from healthy dogs in another study. Reference intervals for the whole sample and for the large samples were determined by a nonparametric method. The estimated reference limits for the small samples were minimum and maximum, mean +/- 2 SD of native and Box-Cox-transformed values, 2.5th and 97.5th percentiles by a robust method on native and Box-Cox-transformed values, and estimates from diagrams of cumulative distribution functions. The whole sample had a heavily skewed distribution, which approached Gaussian after Box-Cox transformation. The reference limits estimated from small samples were highly variable. The closest estimates to the 1439-result reference interval for 27-result subsamples were obtained by both parametric and robust methods after Box-Cox transformation but were grossly erroneous in some cases. For small samples, it is recommended that all values be reported graphically in a dot plot or histogram and that estimates of the reference limits be compared using different methods.

A stratified two-stage sampling design for digital soil mapping in a Mediterranean basin

NASA Astrophysics Data System (ADS)

Blaschek, Michael; Duttmann, Rainer

2015-04-01

The quality of environmental modelling results often depends on reliable soil information. In order to obtain soil data in an efficient manner, several sampling strategies are at hand depending on the level of prior knowledge and the overall objective of the planned survey. This study focuses on the collection of soil samples considering available continuous secondary information in an undulating, 16 km²-sized river catchment near Ussana in southern Sardinia (Italy). A design-based, stratified, two-stage sampling design has been applied aiming at the spatial prediction of soil property values at individual locations. The stratification based on quantiles from density functions of two land-surface parameters - topographic wetness index and potential incoming solar radiation - derived from a digital elevation model. Combined with four main geological units, the applied procedure led to 30 different classes in the given test site. Up to six polygons of each available class were selected randomly excluding those areas smaller than 1ha to avoid incorrect location of the points in the field. Further exclusion rules were applied before polygon selection masking out roads and buildings using a 20m buffer. The selection procedure was repeated ten times and the set of polygons with the best geographical spread were chosen. Finally, exact point locations were selected randomly from inside the chosen polygon features. A second selection based on the same stratification and following the same methodology (selecting one polygon instead of six) was made in order to create an appropriate validation set. Supplementary samples were obtained during a second survey focusing on polygons that have either not been considered during the first phase at all or were not adequately represented with respect to feature size. In total, both field campaigns produced an interpolation set of 156 samples and a validation set of 41 points. The selection of sample point locations has been done using ESRI software (ArcGIS) extended by Hawth's Tools and later on its replacement the Geospatial Modelling Environment (GME). 88% of all desired points could actually be reached in the field and have been successfully sampled. Our results indicate that the sampled calibration and validation sets are representative for each other and could be successfully used as interpolation data for spatial prediction purposes. With respect to soil textural fractions, for instance, equal multivariate means and variance homogeneity were found for the two datasets as evidenced by significant (P > 0.05) Hotelling T²-test (2.3 with df1 = 3, df2 = 193) and Bartlett's test statistics (6.4 with df = 6). The multivariate prediction of clay, silt and sand content using a neural network residual cokriging approach reached an explained variance level of 56%, 47% and 63%. Thus, the presented case study is a successful example of considering readily available continuous information on soil forming factors such as geology and relief as stratifying variables for designing sampling schemes in digital soil mapping projects.

Sampling for Patient Exit Interviews: Assessment of Methods Using Mathematical Derivation and Computer Simulations.

PubMed

Geldsetzer, Pascal; Fink, Günther; Vaikath, Maria; Bärnighausen, Till

2018-02-01

(1) To evaluate the operational efficiency of various sampling methods for patient exit interviews; (2) to discuss under what circumstances each method yields an unbiased sample; and (3) to propose a new, operationally efficient, and unbiased sampling method. Literature review, mathematical derivation, and Monte Carlo simulations. Our simulations show that in patient exit interviews it is most operationally efficient if the interviewer, after completing an interview, selects the next patient exiting the clinical consultation. We demonstrate mathematically that this method yields a biased sample: patients who spend a longer time with the clinician are overrepresented. This bias can be removed by selecting the next patient who enters, rather than exits, the consultation room. We show that this sampling method is operationally more efficient than alternative methods (systematic and simple random sampling) in most primary health care settings. Under the assumption that the order in which patients enter the consultation room is unrelated to the length of time spent with the clinician and the interviewer, selecting the next patient entering the consultation room tends to be the operationally most efficient unbiased sampling method for patient exit interviews. © 2016 The Authors. Health Services Research published by Wiley Periodicals, Inc. on behalf of Health Research and Educational Trust.

Practical guidance on characterizing availability in resource selection functions under a use-availability design

USGS Publications Warehouse

Northrup, Joseph M.; Hooten, Mevin B.; Anderson, Charles R.; Wittemyer, George

2013-01-01

Habitat selection is a fundamental aspect of animal ecology, the understanding of which is critical to management and conservation. Global positioning system data from animals allow fine-scale assessments of habitat selection and typically are analyzed in a use-availability framework, whereby animal locations are contrasted with random locations (the availability sample). Although most use-availability methods are in fact spatial point process models, they often are fit using logistic regression. This framework offers numerous methodological challenges, for which the literature provides little guidance. Specifically, the size and spatial extent of the availability sample influences coefficient estimates potentially causing interpretational bias. We examined the influence of availability on statistical inference through simulations and analysis of serially correlated mule deer GPS data. Bias in estimates arose from incorrectly assessing and sampling the spatial extent of availability. Spatial autocorrelation in covariates, which is common for landscape characteristics, exacerbated the error in availability sampling leading to increased bias. These results have strong implications for habitat selection analyses using GPS data, which are increasingly prevalent in the literature. We recommend researchers assess the sensitivity of their results to their availability sample and, where bias is likely, take care with interpretations and use cross validation to assess robustness.

Characteristics of men with substance use disorder consequent to illicit drug use: comparison of a random sample and volunteers.

PubMed

Reynolds, Maureen D; Tarter, Ralph E; Kirisci, Levent

2004-09-06

Men qualifying for substance use disorder (SUD) consequent to consumption of an illicit drug were compared according to recruitment method. It was hypothesized that volunteers would be more self-disclosing and exhibit more severe disturbances compared to randomly recruited subjects. Personal, demographic, family, social, substance use, psychiatric, and SUD characteristics of volunteers (N = 146) were compared to randomly recruited (N = 102) subjects. Volunteers had lower socioceconomic status, were more likely to be African American, and had lower IQ than randomly recruited subjects. Volunteers also evidenced greater social and family maladjustment and more frequently had received treatment for substance abuse. In addition, lower social desirability response bias was observed in the volunteers. SUD was not more severe in the volunteers; however, they reported a higher lifetime rate of opiate, diet, depressant, and analgesic drug use. Volunteers and randomly recruited subjects qualifying for SUD consequent to illicit drug use are similar in SUD severity but differ in terms of severity of psychosocial disturbance and history of drug involvement. The factors discriminating volunteers and randomly recruited subjects are well known to impact on outcome, hence they need to be considered in research design, especially when selecting a sampling strategy in treatment research.

Progressive sampling-based Bayesian optimization for efficient and automatic machine learning model selection.

PubMed

Zeng, Xueqiang; Luo, Gang

2017-12-01

Machine learning is broadly used for clinical data analysis. Before training a model, a machine learning algorithm must be selected. Also, the values of one or more model parameters termed hyper-parameters must be set. Selecting algorithms and hyper-parameter values requires advanced machine learning knowledge and many labor-intensive manual iterations. To lower the bar to machine learning, miscellaneous automatic selection methods for algorithms and/or hyper-parameter values have been proposed. Existing automatic selection methods are inefficient on large data sets. This poses a challenge for using machine learning in the clinical big data era. To address the challenge, this paper presents progressive sampling-based Bayesian optimization, an efficient and automatic selection method for both algorithms and hyper-parameter values. We report an implementation of the method. We show that compared to a state of the art automatic selection method, our method can significantly reduce search time, classification error rate, and standard deviation of error rate due to randomization. This is major progress towards enabling fast turnaround in identifying high-quality solutions required by many machine learning-based clinical data analysis tasks.

Design and methods of the Midwest Stream Quality Assessment (MSQA), 2013

USGS Publications Warehouse

Garrett, Jessica D.; Frey, Jeffrey W.; Van Metre, Peter C.; Journey, Celeste A.; Nakagaki, Naomi; Button, Daniel T.; Nowell, Lisa H.

2017-10-18

During 2013, the U.S. Geological Survey (USGS) National Water-Quality Assessment Project (NAWQA), in collaboration with the USGS Columbia Environmental Research Center, the U.S. Environmental Protection Agency (EPA) National Rivers and Streams Assessment (NRSA), and the EPA Office of Pesticide Programs assessed stream quality across the Midwestern United States. This Midwest Stream Quality Assessment (MSQA) simultaneously characterized watershed and stream-reach water-quality stressors along with instream biological conditions, to better understand regional stressor-effects relations. The MSQA design focused on effects from the widespread agriculture in the region and urban development because of their importance as ecological stressors of particular concern to Midwest region resource managers.A combined random stratified selection and a targeted selection based on land-use data were used to identify and select sites representing gradients in agricultural intensity across the region. During a 14-week period from May through August 2013, 100 sites were selected and sampled 12 times for contaminants, nutrients, and sediment. This 14-week water-quality “index” period culminated with an ecological survey of habitat, periphyton, benthic macroinvertebrates, and fish at all sites. Sediment was collected during the ecological survey for analysis of sediment chemistry and toxicity testing. Of the 100 sites, 50 were selected for the MSQA random stratified group from 154 NRSA sites planned for the region, and the other 50 MSQA sites were selected as targeted sites to more evenly cover agricultural and urban stressor gradients in the study area. Of the 50 targeted sites, 12 were in urbanized watersheds and 21 represented “good” biological conditions or “least disturbed” conditions. The remaining 17 targeted sites were selected to improve coverage of the agricultural intensity gradient or because of historical data collection to provide temporal context for the study.This report provides a detailed description of the MSQA study components, including surveys of ecological conditions, routine water sampling, deployment of passive polar organic compound integrative samplers, and stream sediment sampling at all sites. Component studies that were completed to provide finer scale temporal data or more extensive analysis at selected sites, included continuous water-quality monitoring, daily pesticide sampling, laboratory and in-stream water toxicity testing efforts, and deployment of passive suspended-sediment samplers.

Efficiency enhancement of optimized Latin hypercube sampling strategies: Application to Monte Carlo uncertainty analysis and meta-modeling

NASA Astrophysics Data System (ADS)

Rajabi, Mohammad Mahdi; Ataie-Ashtiani, Behzad; Janssen, Hans

2015-02-01

The majority of literature regarding optimized Latin hypercube sampling (OLHS) is devoted to increasing the efficiency of these sampling strategies through the development of new algorithms based on the combination of innovative space-filling criteria and specialized optimization schemes. However, little attention has been given to the impact of the initial design that is fed into the optimization algorithm, on the efficiency of OLHS strategies. Previous studies, as well as codes developed for OLHS, have relied on one of the following two approaches for the selection of the initial design in OLHS: (1) the use of random points in the hypercube intervals (random LHS), and (2) the use of midpoints in the hypercube intervals (midpoint LHS). Both approaches have been extensively used, but no attempt has been previously made to compare the efficiency and robustness of their resulting sample designs. In this study we compare the two approaches and show that the space-filling characteristics of OLHS designs are sensitive to the initial design that is fed into the optimization algorithm. It is also illustrated that the space-filling characteristics of OLHS designs based on midpoint LHS are significantly better those based on random LHS. The two approaches are compared by incorporating their resulting sample designs in Monte Carlo simulation (MCS) for uncertainty propagation analysis, and then, by employing the sample designs in the selection of the training set for constructing non-intrusive polynomial chaos expansion (NIPCE) meta-models which subsequently replace the original full model in MCSs. The analysis is based on two case studies involving numerical simulation of density dependent flow and solute transport in porous media within the context of seawater intrusion in coastal aquifers. We show that the use of midpoint LHS as the initial design increases the efficiency and robustness of the resulting MCSs and NIPCE meta-models. The study also illustrates that this relative improvement decreases with increasing number of sample points and input parameter dimensions. Since the computational time and efforts for generating the sample designs in the two approaches are identical, the use of midpoint LHS as the initial design in OLHS is thus recommended.

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.

Occurrence and distribution of methyl tert-butyl ether and other volatile organic compounds in drinking water in the Northeast and Mid-Atlantic regions of the United States, 1993-98

USGS Publications Warehouse

Grady, S.J.; Casey, G.D.

2001-01-01

Data on volatile organic compounds (VOCs) in drinking water supplied by 2,110 randomly selected community water systems (CWSs) in 12 Northeast and Mid-Atlantic States indicate 64 VOC analytes were detected at least once during 1993-98. Selection of the 2,110 CWSs inventoried for this study targeted 20 percent of the 10,479 active CWSs in the region and represented a random subset of the total distribution by State, source of water, and size of system. The data include 21,635 analyses of drinking water collected for compliance monitoring under the Safe Drinking Water Act; the data mostly represent finished drinking water collected at the pointof- entry to, or at more distal locations within, each CWS?s distribution system following any watertreatment processes. VOC detections were more common in drinking water supplied by large systems (serving more than 3,300 people) that tap surface-water sources or both surface- and groundwater sources than in small systems supplied exclusively by ground-water sources. Trihalomethane (THM) compounds, which are potentially formed during the process of disinfecting drinking water with chlorine, were detected in 45 percent of the randomly selected CWSs. Chloroform was the most frequently detected THM, reported in 39 percent of the CWSs. The gasoline additive methyl tert-butyl ether (MTBE) was the most frequently detected VOC in drinking water after the THMs. MTBE was detected in 8.9 percent of the 1,194 randomly selected CWSs that analyzed samples for MTBE at any reporting level, and it was detected in 7.8 percent of the 1,074 CWSs that provided MTBE data at the 1.0-?g/L (microgram per liter) reporting level. As with other VOCs reported in drinking water, most MTBE concentrations were less than 5.0 ?g/L, and less than 1 percent of CWSs reported MTBE concentrations at or above the 20.0-?g/L lower limit recommended by the U.S. Environmental Protection Agency?s Drinking-Water Advisory. The frequency of MTBE detections in drinking water is significantly related to high- MTBE-use patterns. Detections are five times more likely in areas where MTBE is or has been used in gasoline at greater than 5 percent by volume as part of the oxygenated or reformulated (OXY/RFG) fuels program. Detection frequencies of the individual gasoline compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX)) were mostly less than 3 percent of the randomly selected CWSs, but collectively, BTEX compounds were detected in 8.4 percent of CWSs. BTEX concentrations also were low and just three drinkingwater samples contained BTEX at concentrations exceeding 20 ?g/L. Co-occurrence of MTBE and BTEX was rare, and only 0.8 percent of CWSs reported simultaneous detections of MTBE and BTEX compounds. Low concentrations and cooccurrence of MTBE and BTEX indicate most gasoline contaminants in drinking water probably represent nonpoint sources. Solvents were frequently detected in drinking water in the 12-State area. One or more of 27 individual solvent VOCs were detected at any reporting level in 3,080 drinking-water samples from 304 randomly selected CWSs (14 percent) and in 206 CWSs (9.8 percent) at concentrations at or above 1.0 ?g/L. High co-occurrence among solvents probably reflects common sources and the presence of transformation by-products. Other VOCs were relatively rarely detected in drinking water in the 12-State area. Six percent (127) of the 2,110 randomly selected CWSs reported concentrations of 16 VOCs at or above drinking-water criteria. The 127 CWSs collectively serve 2.6 million people. The occurrence of VOCs in drinking water was significantly associated (p<0.0001) with high population- density urban areas. New Jersey, Massachusetts, and Rhode Island, States with substantial urbanization and high population density, had the highest frequency of VOC detections among the 12 States. More than two-thirds of the randomly selected CWSs in New Jersey reported detecting VOC concentrations in drinking water at or above 1

Process to Selectively Distinguish Viable from Non-Viable Bacterial Cells

NASA Technical Reports Server (NTRS)

LaDuc, Myron T.; Bernardini, Jame N.; Stam, Christina N.

2010-01-01

The combination of ethidium monoazide (EMA) and post-fragmentation, randomly primed DNA amplification technologies will enhance the analytical capability to discern viable from non-viable bacterial cells in spacecraft-related samples. Intercalating agents have been widely used since the inception of molecular biology to stain and visualize nucleic acids. Only recently, intercalating agents such as EMA have been exploited to selectively distinguish viable from dead bacterial cells. Intercalating dyes can only penetrate the membranes of dead cells. Once through the membrane and actually inside the cell, they intercalate DNA and, upon photolysis with visible light, produce stable DNA monoadducts. Once the DNA is crosslinked, it becomes insoluble and unable to be fragmented for post-fragmentation, randomly primed DNA library formation. Viable organisms DNA remains unaffected by the intercalating agents, allowing for amplification via post-fragmentation, randomly primed technologies. This results in the ability to carry out downstream nucleic acid-based analyses on viable microbes to the exclusion of all non-viable cells.

The need of adequate information to achieve total compliance of mass drug administration in Pekalongan

NASA Astrophysics Data System (ADS)

Ginandjar, Praba; Saraswati, Lintang Dian; Taufik, Opik; Nurjazuli; Widjanarko, Bagoes

2017-02-01

World Health Organization (WHO) initiated The Global Program to Eliminate Lymphatic Filariasis (LF) through mass drug administration (MDA). Pekalongan started MDA in 2011. Yet the LF prevalence in 2015 remained exceed the threshold (1%). This study aimed to describe the inhibiting factors related to the compliance of MDA in community level. This was a rapid survey with cross sectional approach. A two-stages random sampling was used in this study. In the first stage, 25 clusters were randomly selected from 27 villages with proportionate to population size (PPS) methods (C-Survey). In the second stage, 10 subjects were randomly selected from each cluster. Subject consisted of 250 respondents from 25 selected clusters. Variables consisted of MDA coverage, practice of taking medication during MDA, enabling and inhibiting factors to MDA in community level. The results showed most respondents had poor knowledge on filariasis, which influence awareness of the disease. Health-illness perception, did not receive the drugs, lactation, side effect, and size of the drugs were dominant factors of non-compliance to MDA. MDA information and community empowerment were needed to improve MDA coverage. Further study to explore the appropriate model of socialization will support the success of MDA program

Facebook and Twitter, communication and shelter, and the 2011 Tuscaloosa tornado.

PubMed

Stokes, Courtney; Senkbeil, Jason C

2017-01-01

This paper represents one of the first attempts to analyse the many ways in which Facebook and Twitter were used during a tornado disaster. Comparisons between five randomly selected campus samples and a city of Tuscaloosa, Alabama, sample revealed that campus samples used Facebook and Twitter significantly more both before and after the tornado, but Facebook usage was not significantly different after the event. Furthermore, differences in social media usage and other forms of communication before the tornado were found for age, education, and years lived in Tuscaloosa. Generally, age and education were inversely proportionate to social media usage. Influences on shelter-seeking actions varied between social media users and three random samples of non-social media users; however, it appears that social media respondents were likely to be using a smartphone simultaneously to access warning polygon information, to receive text message alerts, and to listen or respond to environmental cues. © 2017 The Author(s). Disasters © Overseas Development Institute, 2017.

Urinary iodine concentration identifies pregnant women as iodine deficient yet school-aged children as iodine sufficient in rural Niger.

PubMed

Hess, Sonja Y; Ouédraogo, Césaire T; Young, Rebecca R; Bamba, Ibrahim F; Stinca, Sara; Zimmermann, Michael B; Wessells, K Ryan

2017-05-01

To assess iodine status among pregnant women in rural Zinder, Niger and to compare their status with the iodine status of school-aged children from the same households. Seventy-three villages in the catchment area of sixteen health centres were randomly selected to participate in the cross-sectional survey. Salt iodization is mandatory in Niger, requiring 20-60 ppm iodine at the retail level. A spot urine sample was collected from randomly selected pregnant women (n 662) and one school-aged child from the same household (n 373). Urinary iodine concentration (UIC) was assessed as an indicator of iodine status in both groups. Dried blood spots (DBS) were collected from venous blood samples of pregnant women and thyroglobulin (Tg), thyroid-stimulating hormone and total thyroxine were measured. Iodine content of household salt samples (n 108) was assessed by titration. Median iodine content of salt samples was 5·5 ppm (range 0-41 ppm), 98 % had an iodine content 40 µg/l. In this region of Niger, most salt is inadequately iodized. UIC in pregnant women indicated iodine deficiency, whereas UIC of school-aged children indicated marginally adequate iodine status. Thus, estimating population iodine status based solely on monitoring of UIC among school-aged children may underestimate the risk of iodine deficiency in pregnant women.

The Causal Effect of Tracing by Peer Health Workers on Return to Clinic Among Patients Who Were Lost to Follow-up From Antiretroviral Therapy in Eastern Africa: A "Natural Experiment" Arising From Surveillance of Lost Patients.

PubMed

Bershetyn, Anna; Odeny, Thomas A; Lyamuya, Rita; Nakiwogga-Muwanga, Alice; Diero, Lameck; Bwana, Mwebesa; Braitstein, Paula; Somi, Geoffrey; Kambugu, Andrew; Bukusi, Elizabeth; Hartogensis, Wendy; Glidden, David V; Wools-Kaloustian, Kara; Yiannoutsos, Constantin; Martin, Jeffrey; Geng, Elvin H

2017-06-01

The effect of tracing human immunodeficiency virus (HIV)-infected patients who are lost to follow-up (LTFU) on reengagement has not been rigorously assessed. We carried out an ex post analysis of a surveillance study in which LTFU patients were randomly selected for tracing to identify the effect of tracing on reengagement. We evaluated HIV-infected adults on antiretroviral therapy who were LTFU (>90 days late for last visit) at 14 clinics in Uganda, Kenya, and Tanzania. A random sample of LTFU patients was selected for tracing by peer health workers. We assessed the effect of selection for tracing using Kaplan-Meier estimates of reengagement among all patients as well as the subset of LTFU patients who were alive, contacted in person by the tracer, and out of care. Of 5781 eligible patients, 991 (17%) were randomly selected for tracing. One year after selection for tracing, 13.3% (95% confidence interval [CI], 11.1%-15.3%) of those selected for tracing returned compared with 10.0% (95% CI, 9.1%-10.8%) of those not randomly selected, an adjusted risk difference of 3.0% (95% CI, .7%-5.3%). Among patients found to be alive, personally contacted, and out of care, tracing increased the absolute probability of return at 1 year by 22% (95% CI, 7.1%-36.2%). The effect of tracing on rate of return to clinic decayed with a half-life of 7.0 days after tracing (95% CI, 2.6 %-12.9%). Tracing interventions increase reengagement, but developing methods for targeting LTFU patients most likely to benefit can make this practice more efficient. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

Internet and Internet Use: Teacher Trainees' Perspective

ERIC Educational Resources Information Center

Akinoglu, Orhan

2009-01-01

The aim of this study is to present the development and issues of internet and internet use. The study has a descriptive survey design and 185 randomly selected teacher trainees at Marmara University, Ataturk Education Faculty in the 2001-2002 academic year constitute the sample. Data were collected via a questionnaire prepared by the researcher…

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…

Vietnamese Amerasians: Practical Implications of Current Research.

ERIC Educational Resources Information Center

Felsman, J. Kirk.; And Others

This study was conducted to examine the experiences of Amerasians from Vietnam who resettled in the United States and to explore coping and adaptation among Vietnamese Amerasians over time. The initial data collection phase involved in-camp assessment of a randomly selected sample of Amerasian adolescents (N=259). The assessment is to be repeated…

ASSESSMENT OF THE WRITTEN LANGUAGE OF DEAF STUDENTS.

ERIC Educational Resources Information Center

MARKS, CLAUDE H.; STUCKLESS, E. ROSS

THIS INVESTIGATION WAS CONDUCTED TO DESCRIBE THE WRITTEN LANGUAGE OF DEAF STUDENTS BETWEEN 10 AND 18 YEARS OF AGE IN TERMS OF SIX MEASURABLE VARIABLES, AND TO RELATE THESE VARIABLES TO TEACHER JUDGMENTS OF QUALITY OF LANGUAGE. TEN STRATIFIED RANDOM SAMPLES OF COMPOSITIONS BY DEAF STUDENTS WERE SELECTED FROM 14 RESIDENTIAL AND DAY EDUCATIONAL…

42 CFR 416.140 - Surveys.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 42 Public Health 3 2014-10-01 2014-10-01 false Surveys. 416.140 Section 416.140 Public Health... Furnished Before January 1, 2008 § 416.140 Surveys. (a) Timing, purpose, and procedures. (1) No more often than once a year, CMS conducts a survey of a randomly selected sample of participating ASCs to collect...

42 CFR 416.140 - Surveys.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 42 Public Health 3 2011-10-01 2011-10-01 false Surveys. 416.140 Section 416.140 Public Health... January 1, 2008 § 416.140 Surveys. (a) Timing, purpose, and procedures. (1) No more often than once a year, CMS conducts a survey of a randomly selected sample of participating ASCs to collect data for analysis...

42 CFR 416.140 - Surveys.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 42 Public Health 3 2013-10-01 2013-10-01 false Surveys. 416.140 Section 416.140 Public Health... Furnished Before January 1, 2008 § 416.140 Surveys. (a) Timing, purpose, and procedures. (1) No more often than once a year, CMS conducts a survey of a randomly selected sample of participating ASCs to collect...

42 CFR 416.140 - Surveys.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 42 Public Health 3 2012-10-01 2012-10-01 false Surveys. 416.140 Section 416.140 Public Health... Furnished Before January 1, 2008 § 416.140 Surveys. (a) Timing, purpose, and procedures. (1) No more often than once a year, CMS conducts a survey of a randomly selected sample of participating ASCs to collect...

42 CFR 416.140 - Surveys.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 42 Public Health 3 2010-10-01 2010-10-01 false Surveys. 416.140 Section 416.140 Public Health... January 1, 2008 § 416.140 Surveys. (a) Timing, purpose, and procedures. (1) No more often than once a year, CMS conducts a survey of a randomly selected sample of participating ASCs to collect data for analysis...

78 FR 20320 - Agency Information Collection Activities: Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-04

...: select from for a random sample, get the survey to the appropriate respondent, and increase response rates. The survey will not be added to this package; instead, it will be processed under a different... Medicaid Services is requesting clearance for two surveys to aid in understanding levels of awareness and...

Influence of the Pedagogical Context on Students' Evaluation of Teaching

ERIC Educational Resources Information Center

Luna, Edna; Aramburo, Vicente; Cordero, Graciela

2010-01-01

The purpose of this study was to compare the characteristics of teaching performance in accordance with the opinion of students of different academic fields and curriculum stages in a Mexican state public university. The sample was composed of 729 randomly-selected courses, distributed over four semester periods. Descriptive and comparative…

Improving EFL Learners' Pronunciation of English through Quiz-Demonstration-Practice-Revision (QDPR)

ERIC Educational Resources Information Center

Moedjito

2018-01-01

This study investigates the effectiveness of Quiz-Demonstration-Practice-Revision (QDPR) in improving EFL learners' pronunciation of English. To achieve the goal, the present researcher conducted a one-group pretest-posttest design. The experimental group was selected using a random sampling technique with consideration of the inclusion criteria.…

Logging utilization in Idaho: Current and past trends

Treesearch

Eric A. Simmons; Todd A. Morgan; Erik C. Berg; Stanley J. Zarnoch; Steven W. Hayes; Mike T. Thompson

2014-01-01

A study of commercial timber-harvesting activities in Idaho was conducted during 2008 and 2011 to characterize current tree utilization, logging operations, and changes from previous Idaho logging utilization studies. A two-stage simple random sampling design was used to select sites and felled trees for measurement within active logging sites. Thirty-three logging...

Sexuality Education Beliefs among Sexually Experienced Youth: Differences by Gender and Birth Control Use

ERIC Educational Resources Information Center

Tolma, Eleni L.; Vesely, Sara K.; Oman, Roy F.; Aspy, Cheryl B.; Rodine, Sharon

2006-01-01

Purpose: To examine whether gender and birth control use are associated with premarital sexual attitudes, beliefs about peers, family communication about sexual relationships, and sexuality education among sexually experienced youth. Methods: Data were collected from a randomly selected ethnically diverse youth sample (N = 1,253). Only the…

Taking the Next Step: Combining Incrementally Valid Indicators to Improve Recidivism Prediction

ERIC Educational Resources Information Center

Walters, Glenn D.

2011-01-01

The possibility of combining indicators to improve recidivism prediction was evaluated in a sample of released federal prisoners randomly divided into a derivation subsample (n = 550) and a cross-validation subsample (n = 551). Five incrementally valid indicators were selected from five domains: demographic (age), historical (prior convictions),…

Validity of a Checklist for the Design, Content, and Instructional Qualities of Children's Books

ERIC Educational Resources Information Center

Çer, Erkan; Sahin, Ertugrul

2016-01-01

The purpose of this study was to develop a checklist whose validity has been tested in assessing children's books. Participants consisted of university students who had taken a course in children's literature. They were selected through convenience sampling and randomly assigned into experimental and control groups. Participants in the…

State Self-Esteem in Relation to Weight Locus of Control amongst Adolescents

ERIC Educational Resources Information Center

Rattan, Neelam; Kang, Shirin; Thakur, Nisha; Parthi, Komila

2006-01-01

The current society emphasizes physical appearance and physical fitness. Individual's self-esteem has been shown to be linked with physical appearance. Methods: A random sample comprising of 100 male and 100 female (N = 200) adolescents was selected. The subjects were administered the Current Thoughts Scale and the Dieting Beliefs Scale for…

Parent-Infant Vocalisations at 12 Months Predict Psychopathology at 7 Years

ERIC Educational Resources Information Center

Allely, C. S.; Purves, D.; McConnachie, A.; Marwick, H.; Johnson, P.; Doolin, O.; Puckering, C.; Golding, J.; Gillberg, C.; Wilson, P.

2013-01-01

This study investigated the utility of adult and infant vocalisation in the prediction of child psychopathology. Families were sampled from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. Vocalisation patterns were obtained from 180 videos (60 cases and 120 randomly selected sex-matched controls) of parent-infant…

Using Chemistry Simulations: Attention Capture, Selective Amnesia and Inattentional Blindness

ERIC Educational Resources Information Center

Rodrigues, Susan

2011-01-01

Twenty-one convenience sample student volunteers aged between 14-15 years worked in pairs (and one group of three) with two randomly allocated high quality conceptual (molecular level) and operational (mimicking wet labs) simulations. The volunteers were told they had five minutes to play, repeat, review, restart or stop the simulation, which in…

Exceptional Children and Microcomputers, A Survey of Public School Applications.

ERIC Educational Resources Information Center

Crowner, T. Timothy

Telephone interviews on the use of microcomputers in special education were administered to personnel in 25 districts (drawn from a random sample of the largest school districts in the United States) on the following topics: coordination of microcomputers; numbers of microcomputers owned and used; pragmatic uses; funding; brands used; selection,…

Phase IV: Educational Needs Assessment For Washington State Students. March 1973. (Summary).

ERIC Educational Resources Information Center

Brouillet, Frank B.

The results of the Washington Elementary Educational Assessment Project (WEEAP) are presented in this report. The purposes of the Assessment project were (1) to assess the reading and mathematics achievement in Washington elementary schools by sampling fourth and sixth grade students in randomly selected school buildings; (2) to identify…

Concordance among Physical Educators', Teachers', and Parents' Perceptions of Attention Problems in Children

ERIC Educational Resources Information Center

Efstratopoulou, Maria; Simons, Johan; Janssen, Rianne

2013-01-01

Objective: The study examined the concordance among rating sources on attention problems of elementary school-aged children. Method: A randomly selected sample ("N" = 841) of children was rated by the physical educators, the teachers, and the parents, using the Attention Scales of the Motor Behavior Checklist (MBC), the Teacher Report…

MPA and CPM Curriculum: An Analysis of the Views of Public Administrators.

ERIC Educational Resources Information Center

Rose, Bruce J.

Views of state public administrators about management education and training needs were investigated, as were administrator views concerning short-term management development workshops. Data was drawn from responses to questionnaires mailed to 5,980 state administrators who were selected from a national survey and from random samples using lists…

Evaluation of LEAA Funded Courts Training Programs. Volume I.

ERIC Educational Resources Information Center

McManis Associates, Inc., Washington, DC.

An impact evaluation of eight courts training project (CTP) institutes funded by the Law Enforcement Assistance Administration was conducted. After a literature search and visits to potential evaluation sites in all fifty states, twelve sites were selected from a random stratified sample of court systems. Data were obtained from 1047 respondents…

Correlates of Young Adult Tobacco Use: Application of a Transition Framework

ERIC Educational Resources Information Center

Lenz, Brenda K.

2003-01-01

Anticipatory guidance is a traditional nursing intervention. The purpose of this study was to identify factors to serve as targets for anticipatory guidance prior to high school graduation to reduce tobacco initiation among young adults after graduation. A sample of 203 randomly selected freshmen and sophomore students at a major midwestern…

A Study of Teachers' Perception of Schools' Organizational Health in Osun State

ERIC Educational Resources Information Center

Omoyemiju, Michael Adeniyi; Adediwura, Alaba Adeyemi

2011-01-01

This study examined the teachers' perceptions of school organizational health (i.e. resource support, job satisfaction among staff, morale boosts, institutional integrity and initiating structure). Descriptive survey design was used for the study. The sample was composed of 330 secondary school teachers randomly selected from 283, 826 secondary…

An Analysis of Young Children Learning Keyboarding Skills.

ERIC Educational Resources Information Center

Cowles, Milly; And Others

The primary purpose of this study was to demonstrate whether children ages 5 through 8 could learn keyboarding skills. A secondary purpose was to examine the relationship between typing skill development and motor proficiency. A sample of 24 children was randomly selected from a group attending a summer school enrichment program. The…

Enhancing English Learners' Willingness to Communicate through Debate and Philosophy Inquiry Discussion

ERIC Educational Resources Information Center

Shamsudin, Mardziah; Othman, Moomala; Jahedi, Maryam; Aralas, Dalia

2017-01-01

The present study investigated the impact of two instructional methods, Debate and Philosophy Inquiry (PI), in enhancing Willingness to Communicate (WTC) among two groups of English as a Second Language (ESL) learners who were randomly selected. In each group there were sixteen participants. The researchers used independent samples t-test and…

Dual Use of Cigarettes and Smokeless Tobacco among South African Adolescents

ERIC Educational Resources Information Center

Rantao, Masego; Ayo-Yusuf, Olalekan A.

2012-01-01

Objectives: To determine factors associated with dual use of tobacco products in a population of black South African adolescents. Methods: Data were obtained from a self-administered questionnaire completed by a representative sample of grade 8 students from 21 randomly selected secondary state schools in the Limpopo Province, South Africa (n =…

The King Pre-Retirement Checklist: Assessing Differences in Pre-Retirement Planning.

ERIC Educational Resources Information Center

Zitzow, Darryl; King, Donald N.

In an effort to assess the retirement preparedness of Midwestern populations above the age of 28, the King Pre-Retirement Checklist was administered to a sampling of 458 persons randomly selected and proportionally stratified by geographic location and community size. Factors examined were financial, social, family cohesion, mobility/health,…

Barriers to Distance Education in Rural Schools

ERIC Educational Resources Information Center

Irvin, Matthew J.; Hannum, Wallace H.; Varre, Claire de la; Farmer, Thomas W.

2010-01-01

The primary purpose of the current study was to examine barriers to the use of distance education and explore related factors in small and low-income rural schools. Data were collected via a telephone survey with administrators or other qualified personnel. The sample involved 417 randomly selected small and low-income rural school districts…

Approaches to Building Teacher-Parent Cooperation

ERIC Educational Resources Information Center

Cankar, Franc; Deutsch, Tomi; Sentocnik, Sonja

2012-01-01

The purpose of this study was to explore the areas of cooperation in which parent and teacher expectations were the same and where they differed. Data were obtained from a sample of 55 randomly selected primary schools. We analyzed school-to home communications, parental influence on school decisions, and parent involvement in different school…

Influences on Students Selecting Cooperative Education Programs in Michigan High Schools. Final Report.

ERIC Educational Resources Information Center

Woloszyk, Carl A.

Factors influencing the decision of high school students to enroll in cooperative education programs were investigated in a survey. The stratified random sample consisted of 275 high school students currently enrolled in cooperative education programs in five different types of communities throughout Michigan. The survey questionnaire included 8…

Off-Farm Agricultural Occupations in Montana: Employment and Education.

ERIC Educational Resources Information Center

Heaney, Donald S.

Data were obtained by interview with managers in a random sample of 161 businesses in 10 selected Montana trade and service centers to (1) identify present and emerging off-farm agricultural occupations, (2) estimate present and anticipated numbers of employees, (3) estimate annual entry opportunities, (4) determine needed competencies, and (5)…

Impact Evaluation of Further Mathematics Curriculum in Nigeria

ERIC Educational Resources Information Center

Odili, Godwin Alo; Asuru, Vincent A.

2011-01-01

This research was a perceptual survey study carried out to determine whether the goals of Further Mathematics Curriculum (FMC) are being achieved at the Senior Secondary School level. The sample for the study consisted of 240 FM final year students, 45 FM teachers and 180 undergraduates who were selected by a multistage stratified random sampling…

Cigarette and Nargileh Smoking Practices among School Students in Beirut, Lebanon

ERIC Educational Resources Information Center

Tamim, Hala; Al-Sahab, Ban; Akkary, Ghassan; Ghanem, Mary; Tamim, Nada; El Roueiheb, Zana; Kanj, Mayada; Afifi, Rima

2007-01-01

Objectives: To determine the prevalence and predictors of smoking nargileh and/or cigarettes among school students in Greater Beirut, Lebanon. Methods: A proportionate random sample of 2443 students from 13 public and private schools was selected and asked to complete self-administered anonymous questionnaires. Results: The prevalence of smoking…

Behavioural Problems of Juvenile Street Hawkers in Uyo Metropolis, Nigeria

ERIC Educational Resources Information Center

Udoh, Nsisong A.; Joseph, Eme U.

2012-01-01

The study sought the opinions of Faculty of Education Students of University of Uyo on the behavioural problems of juvenile street hawkers in Uyo metropolis. Five research hypotheses were formulated to guide the study. This cross-sectional survey employed multi-stage random sampling technique in selecting 200 regular undergraduate students in the…

Prevalence and Correlates of Elder Mistreatment in South Carolina: The South Carolina Elder Mistreatment Study

ERIC Educational Resources Information Center

Amstadter, Ananda B.; Zajac, Kristyn; Strachan, Martha; Hernandez, Melba A.; Kilpatrick, Dean G.; Acierno, Ron

2011-01-01

The purposes of this study were to (a) derive prevalence estimates for elder mistreatment (emotional, physical, sexual, neglectful, and financial mistreatment of older adults [age 60 +]) in a randomly selected sample of South Carolinians; (b) examine correlates (i.e., potential risk factors) of mistreatment; and (c) examine incident…

Legal Implications for Teacher Selection as Defined by the ADA and the ADEA.

ERIC Educational Resources Information Center

Young, I. Phillip; Prince, Arthur L.

1999-01-01

Hypothetical teacher candidates were created, some of whom were depicted as having an acknowledged disability, others having no acknowledged disability and all varied with respect to chronological age. A national random sample of public school principals evaluated the teacher candidates as if screening for a vacant position within their school…

Relationship between High School Students' Facebook Addiction and Loneliness Status

ERIC Educational Resources Information Center

Karakose, Turgut; Yirci, Ramazan; Uygun, Harun; Ozdemir, Tuncay Yavuz

2016-01-01

This study was conducted in order to analyze the relation between high school students' Facebook addiction and loneliness levels. The study was conducted with the relational screening model. The sample of the study consists of 712 randomly selected high school students. The data was collected using the Bergen Facebook Addiction Scale (BFAS) to…

Public-Private Partnership and Infrastructural Development in Nigerian Universities

ERIC Educational Resources Information Center

Oduwaiye, R. O.; Sofoluwe, A. O.; Bello, T. O.; Durosaro, I. A.

2014-01-01

This study investigated the degree to which Public-Private Partnership (PPP) services are related to infrastructural development in Nigerian Universities. The research design used was descriptive survey method. The population for the study encompassed all the 20 universities in South-west Nigeria. Stratified random sampling was used to select 12…

Health Literacy in College Students

ERIC Educational Resources Information Center

Ickes, Melinda J.; Cottrell, Randall

2010-01-01

Objective: The purpose of this study was to assess the health literacy levels, and the potential importance of healthy literacy, of college students. Participants: Courses were randomly selected from all upper level undergraduate courses at a large Research I university to obtain a sample size of N = 399. Methods: During the 2007-2008 school year,…

Adolescent Sexuality Related Beliefs and Differences by Sexual Experience Status

ERIC Educational Resources Information Center

Tolma, Eleni L.; Oman, Roy F.; Vesely, Sara K.; Aspy, Cheryl B.; Rodine, Sharon; Marshall, LaDonna; Fluhr, Janene

2007-01-01

Purpose: To examine if attitudes toward premarital sex, beliefs about peer influence, and family communication about sexual relationships differ by sexual experience status. Methods: Data were collected from a randomly selected ethnically diverse youth sample (N = 1,318) residing in two Midwestern cities. The primary method used in data analysis…

Cigarette Smoking and Anti-Smoking Counseling Practices among Physicians in Wuhan, China

ERIC Educational Resources Information Center

Gong, Jie; Zhang, Zhifeng; Zhu, Zhaoyang; Wan, Jun; Yang, Niannian; Li, Fang; Sun, Huiling; Li, Weiping; Xia, Jiang; Zhou, Dunjin; Chen, Xinguang

2012-01-01

Purpose: The paper seeks to report data on cigarette smoking, anti-smoking practices, physicians' receipt of anti-smoking training, and the association between receipt of the training and anti-smoking practice among physicians in Wuhan, China. Design/methodology/approach: Participants were selected through the stratified random sampling method.…

Examining Middle School Students' Views on Text Bullying

ERIC Educational Resources Information Center

Semerci, Ali

2016-01-01

This study aimed to examine middle school students' views on text bullying in regard to gender, grade level, reactions to bullying and frequency of internet use. The participating 872 students were selected through simple random sampling method among 525 schools located in central Ankara. The data were collected via a questionnaire and a survey…

Preliminary Findings on Rural Homelessness in Ohio.

ERIC Educational Resources Information Center

First, Richard J.; And Others

This report is designed to present preliminary findings from the first comprehensive study of rural homelessness in the United States. The study was conducted during the first 6 months of 1990, and data were collected from interviews with 921 homeless adults in 21 randomly selected rural counties in Ohio. The sample counties represent 26% of the…

Play Therapy Training among School Psychology, Social Work, and School Counseling Graduate Training Programs

ERIC Educational Resources Information Center

Pascarella, Christina Bechle

2012-01-01

This study examined play therapy training across the nation among school psychology, social work, and school counseling graduate training programs. It also compared current training to previous training among school psychology and school counseling programs. A random sample of trainers was selected from lists of graduate programs provided by…

Tobacco, Depression, and Lifestyle Choices in the Pivotal Early College Years

ERIC Educational Resources Information Center

Lenz, Brenda K.

2004-01-01

The author explored the correlates of tobacco use among 18-and 19-year-old students at a major midwestern university. A sample of 203 randomly selected freshmen and sophomore students completed a survey that included questions about tobacco use, other drug use, mental health issues, eating disorders, stress, smoking environment, and healthy…

Epidemiology of Attention Problems among Turkish Children and Adolescents: A National Study

ERIC Educational Resources Information Center

Erol, Nese; Simsek, Zeynep; Oner, Ozgur; Munir, Kerim

2008-01-01

Objective: To evaluate the epidemiology of attention problems using parent, teacher, and youth informants among a nationally representative Turkish sample. Method: The children and adolescents, 4 to 18 years old, were selected from a random household survey. Attention problems derived from the Child Behavior Checklist (CBCL) (N = 4,488), Teacher…

49 CFR 178.819 - Vibration test.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration test. 178.819 Section 178.819... Testing of IBCs § 178.819 Vibration test. (a) General. The vibration test must be conducted for the... vibration test. (b) Test method. (1) A sample IBC, selected at random, must be filled and closed as for...

Sticker Shock: Management Professors' Perspectives on the Rising Costs of College Textbooks

ERIC Educational Resources Information Center

Williamson, Stan; Stevens, Robert E.; Silver, Lawrence S.; Clow, Kenneth E.

2011-01-01

This study uses Internet survey methodology to target management instructors' views on the cost of textbooks and the strategies that might be exercised by universities, publishers, and legislatures to control cost increases. From a random sample of 2,893 management professors selected, using university websites, from universities throughout the…

Subversion of the American Family? An Examination of Children and Parents in Television Families.

ERIC Educational Resources Information Center

Douglas, William; Olson, Beth M.

1996-01-01

Examines the portrayal of family relationships in television domestic comedy. States that subjects were randomly selected to evaluate samples of nine programs. Finds that on television both parent-child and sibling relationships have developed in relational frameworks defined by the changing levels of conflict, cohesiveness, and socializing, with…

Prevalence of Human Immunodeficiency Virus Testing and Associated Risk Factors in College Students

ERIC Educational Resources Information Center

Dennison, Olivia; Wu, Qishan; Ickes, Melinda

2014-01-01

Objective: This study documents the prevalence of human immunodeficiency virus (HIV) testing in a sample of college students and examines associated demographic and behavioral characteristics. Participants: College students aged 18 or older were randomly selected to participate in a health behavior survey at a southeastern university in September…

Anemia, micronutrient deficiencies, and malaria in children and women in Sierra Leone prior to the Ebola outbreak

USDA-ARS?s Scientific Manuscript database

To identify the factors associated with anemia and to document the severity of micronutrient deficiencies, malaria and inflammation, a nationally representative cross-sectional survey was conducted. A three-stage sampling procedure was used to randomly select children <5 years of age and adult women...

Internal Challenges Affecting Academic Performance of Student-Athletes in Ghanaian Public Universities

ERIC Educational Resources Information Center

Apaak, Daniel; Sarpong, Emmanuel Osei

2015-01-01

This paper examined internal challenges affecting academic performance of student-athletes in Ghanaian public universities, using a descriptive survey research design. Proportionate random sampling technique was employed to select Three Hundred and Thirty-Two (332) respondents for the study. The instrument used in gathering data for the study was…

Reference List Accuracy in Social Work Journals: A Follow-Up Analysis

ERIC Educational Resources Information Center

Mitchell-Williams, Missy T.; Skipper, Antonius D.; Alexander, Marvin C.; Wilks, Scott E.

2017-01-01

Purpose: Following up an "Research on Social Work Practice" article published a decade ago, this study aimed to examine reference error rates among five, widely circulated social work journals. Methods: A stratified random sample of references was selected from the year 2013 (N = 500, 100/journal). Each was verified against the original…

Primary Teacher Trainees Preparedness to Teach Science: A Gender Perspective

ERIC Educational Resources Information Center

Mutisya, Sammy M.

2015-01-01

The purpose of this study was to determine Primary Teacher Education (PTE) Trainees' perceptions regarding their preparedness to teach science in primary schools. A descriptive survey research design was used and stratified proportionate random sampling techniques used to select 177 males and 172 females. The study found out that more male trainee…

Enrolled Nurses: A Study for the UKCC.

ERIC Educational Resources Information Center

Seccombe, I.; Smith, G.; Buchan, J.; Ball, J.

Selected issues of concern to second-level enrolled (registered) nurses in the United Kingdom were examined through national surveys of two groups: (1) a random sample of 21,762 of the 115,459 nurses holding second-level registration in the United Kingdom, and (2) 700 employers who, included nurse executive directors in all National Health Service…

Exploring Bullying: An Early Childhood Perspective from Mainland China

ERIC Educational Resources Information Center

Arndt, Janet S.; Luo, Nili

2008-01-01

This article explores bullying in mainland China. The authors conducted a study to determine the existence of a problem with bullying in younger Chinese children. Samples included 40 randomly selected, early childhood educators serving children ages 2 through 6, located in 10 different urban school settings along the Yangzi River. The authors…

77 FR 40345 - Proposed Agency Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-09

... and Security Act and signed into law on December 19, 2007, was funded for the first time by the ARRA... applied to select 350 grants for study. That random sample of projects will be taken from the six Broad... program impacts and other metrics. Also contains a series of questions related to grant performance not...

Monitoring Achievement of Educational Governance/Management Policy Goals.

ERIC Educational Resources Information Center

Sederberg, Charles H.; Hendrix, Vernon L.

This paper reports on a field test of a system for monitoring the achievement of selected educational governance/management goals. The study entailed (1) collection of enrollment, revenue, expenditure, and teacher assignment data from a stratified random sample of Minnesota districts for a seven-year period, 1969-70 through 1975-76; (2) reduction…

Social Attitudes and Educational Needs of Women in the Chaffey Community College District.

ERIC Educational Resources Information Center

Lyman-Viera, Karen A.; Boggs, John

A socio-economically stratified sample of 368 randomly selected adult women residents of the Chaffey College district were interviewed to determine their demographic characteristics, educational needs and interests, perceived barriers to educational participation, and the adequacy of current college programs to meet the needs of women. Results of…

Evaluation of Residential Consumers Knowledge of Wireless Network Security and Its Correlation with Identity Theft

ERIC Educational Resources Information Center

Kpaduwa, Fidelis Iheanyi

2010-01-01

This current quantitative correlational research study evaluated the residential consumers' knowledge of wireless network security and its relationship with identity theft. Data analysis was based on a sample of 254 randomly selected students. All the study participants completed a survey questionnaire designed to measure their knowledge of…

The Physical, Environmental, and Intellectual Profile of the Fifth Grade Navajo.

ERIC Educational Resources Information Center

Tempest, Phyllis

1987-01-01

A random sample of 222 Navajo fifth graders from the Navajo Reservation were selected from eight schools and given an extensive battery of tests to determine intelligence, academic achievement, physical health, and environmental conditions. Results produced an average Navajo learning profile to which other Reservation Navajo students can be…

Early Adolescent Outcomes of Institutionally Deprived and Non-Deprived Adoptees. III. Quasi-Autism

ERIC Educational Resources Information Center

Rutter, Michael; Kreppner, Jana; Croft, Carla; Murin, Marianna; Colvert, Emma; Beckett, Celia; Castle, Jenny; Sonuga-Barke, Edmund

2007-01-01

Background: Some young children reared in profoundly depriving institutions have been found to show autistic-like patterns, but the developmental significance of these features is unknown. Methods: A randomly selected, age-stratified, sample of 144 children who had experienced an institutional upbringing in Romania and who were adopted by UK…

Relationships between Teacher Organizational Commitment, Psychological Hardiness and Some Demographic Variables in Turkish Primary Schools

ERIC Educational Resources Information Center

Sezgin, Ferudun

2009-01-01

Purpose: The purpose of this paper is to examine the relationships between teachers' organizational commitment perceptions and both their psychological hardiness and some demographic variables in a sample of Turkish primary schools. Design/methodology/approach: A total of 405 randomly selected teachers working at primary schools in Ankara…

Relationship between Principals Administrative Strategies and Student Disciplinary Problems in Secondary School, Bayelsa State

ERIC Educational Resources Information Center

Omemu, Felix

2017-01-01

This study examined the relationship between administrative strategy by principals and their effectiveness in tackling disciplinary problems. Three research questions were asked and one hypothesis was raised and tested at 0.05 level of significance. Ninety-five randomly selected principals from Bayelsa State constitute the sample. The instrument…

The Relationship between Prospective Teachers' Critical Thinking Dispositions and Their Educational Philosophies

ERIC Educational Resources Information Center

Aybek, Birsel; Aslan, Serkan

2017-01-01

The aim of this research is to investigate the relationship between prospective teachers' critical thinking dispositions and their educational philosophies. The research used relational screening model. The study hosts a total of 429 prospective teachers selected by the simple random sampling method. Research data has been collected through…

Psychosocial Determinants of Conflict-Handling Behaviour of Workers in Oil Sector in Nigeria

ERIC Educational Resources Information Center

Bankole, Akanji Rafiu

2011-01-01

The study examined the joint and relative influence of three psychosocial factors: Emotional intelligence, communication skill and interpersonal skill on conflict-handling behaviour of oil workers in Nigeria. Survey research design was adopted and a sample of 610 workers was randomly selected from oil companies across the country. Data were…

1989 Student Survey Results: HIV-Related Knowledge, Attitudes, and Behaviors. Summary.

ERIC Educational Resources Information Center

Colorado State Dept. of Education, Denver.

In 1989, the Colorado Department of Education, in cooperation with the Centers for Disease Control, administered the Acquired Immune Deficiency Syndrome/Human Immunodeficiency Virus (AIDS/HIV) Student Survey to randomly selected Colorado students (1,851), excluding the Denver Public Schools, grades 9-12. The sample was fairly equally divided by…

An Investigation on Secondary School Students' Attitude towards Science in Ogun State, Nigeria

ERIC Educational Resources Information Center

Sakariyau, A. O.; Taiwo, Michael O.; Ajagbe, Olalere W.

2016-01-01

The study investigated the attitudes of secondary school students towards science in Odeda Local Government Area of Ogun State, Nigeria. Two hundred senior secondary school students consisting of 84 males and 116 females were selected from five secondary schools using stratified random sampling techniques. A 20-item Attitude to Science…

Sex Stereotypes and School Adolescents' Sexual Behaviour in Osun State, Nigeria

ERIC Educational Resources Information Center

Popoola, Bayode Isaiah

2011-01-01

This study investigated the association between sex stereotypes and the sexual behaviour of Nigerian school-going adolescents. It also ascertained the effects of age and sex on adolescents' beliefs about sex stereotypes. The study sample consisted of 658 (male = 287, female = 371) adolescents from nine randomly selected secondary schools in three…

Predictors of Career Adaptability Skill among Higher Education Students in Nigeria

ERIC Educational Resources Information Center

Ebenehi, Amos Shaibu; Rashid, Abdullah Mat; Bakar, Ab Rahim

2016-01-01

This paper examined predictors of career adaptability skill among higher education students in Nigeria. A sample of 603 higher education students randomly selected from six colleges of education in Nigeria participated in this study. A set of self-reported questionnaire was used for data collection, and multiple linear regression analysis was used…

Why Do Counselors Return to Work at Camp?

ERIC Educational Resources Information Center

Becker, William A.

The reasons that counselors in resident summer camps return to work are explored, taking into account the differences between private and agency camps, and differing attitudes of male and female camp counselors. A random sample of returning counselors at 15 private and 15 agency camps in the Northeast were selected for the study. Six attitudinal…

HIV/AIDS-Anxiety among Adolescent Students in Botswana

ERIC Educational Resources Information Center

Onyewadume, Mary Adeola

2008-01-01

This research investigated the incidence of HIV/AIDS anxiety among students in Botswana. The sample comprised 240 randomly selected students from six schools in three districts in Botswana, with data collected via a questionnaire. Percentages and Chi-square were used to analyze the extent to which the students were anxious about HIV/AIDS and if…

Do nonexercisers also share the positive exerciser stereotype?: An elicitation and comparison of beliefs about exercisers.

PubMed

Rodgers, Wendy M; Hall, Craig R; Wilson, Philip M; Berry, Tanya R

2009-02-01

The purpose of this research was to examine whether exercisers and nonexercisers are rated similarly on a variety of characteristics by a sample of randomly selected regular exercisers, nonexercisers who intend to exercise, and nonexercisers with no intention to exercise. Previous research by Martin Ginis et al. (2003) has demonstrated an exerciser stereotype that advantages exercisers. It is unknown, however, the extent to which an exerciser stereotype is shared by nonexercisers, particularly nonintenders. Following an item-generation procedure, a sample of 470 (n=218 men; n=252 women) people selected using random digit dialing responded to a questionnaire assessing the extent to which they agreed that exercisers and nonexercisers possessed 24 characteristics, such as "happy," "fit," "fat," and "lazy." The results strongly support a positive exerciser bias, with exercisers rated more favorably on 22 of the 24 items. The degree of bias was equivalent in all groups of respondents. Examination of the demographic characteristics revealed no differences among the three groups on age, work status, or child-care responsibilities, suggesting that there is a pervasive positive exerciser bias.

Topology in two dimensions. II - The Abell and ACO cluster catalogues

NASA Astrophysics Data System (ADS)

Plionis, Manolis; Valdarnini, Riccardo; Coles, Peter

1992-09-01

We apply a method for quantifying the topology of projected galaxy clustering to the Abell and ACO catalogues of rich clusters. We use numerical simulations to quantify the statistical bias involved in using high peaks to define the large-scale structure, and we use the results obtained to correct our observational determinations for this known selection effect and also for possible errors introduced by boundary effects. We find that the Abell cluster sample is consistent with clusters being identified with high peaks of a Gaussian random field, but that the ACO shows a slight meatball shift away from the Gaussian behavior over and above that expected purely from the high-peak selection. The most conservative explanation of this effect is that it is caused by some artefact of the procedure used to select the clusters in the two samples.

A Critical Assessment of Bias in Survey Studies Using Location-Based Sampling to Recruit Patrons in Bars

PubMed Central

Morrison, Christopher; Lee, Juliet P.; Gruenewald, Paul J.; Marzell, Miesha

2015-01-01

Location-based sampling is a method to obtain samples of people within ecological contexts relevant to specific public health outcomes. Random selection increases generalizability, however in some circumstances (such as surveying bar patrons) recruitment conditions increase risks of sample bias. We attempted to recruit representative samples of bars and patrons in six California cities, but low response rates precluded meaningful analysis. A systematic review of 24 similar studies revealed that none addressed the key shortcomings of our study. We recommend steps to improve studies that use location-based sampling: (i) purposively sample places of interest, (ii) utilize recruitment strategies appropriate to the environment, and (iii) provide full information on response rates at all levels of sampling. PMID:26574657

47 CFR 1.1602 - Designation for random selection.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Designation for random selection. 1.1602 Section 1.1602 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE Random Selection Procedures for Mass Media Services General Procedures § 1.1602 Designation for random selection...

47 CFR 1.1602 - Designation for random selection.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Designation for random selection. 1.1602 Section 1.1602 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE Random Selection Procedures for Mass Media Services General Procedures § 1.1602 Designation for random selection...

Consumer assessment of beef tenderloin steaks from various USDA quality grades at 3 degrees of doneness.

PubMed

O'Quinn, Travis G; Brooks, J Chance; Miller, Markus F

2015-02-01

A consumer study was conducted to determine palatability ratings of beef tenderloin steaks from USDA Choice, USDA Select, and USDA Select with marbling scores from Slight 50 to 100 (USDA High Select) cooked to various degrees of doneness. Steaks were randomly assigned to 1 of 3 degree of doneness categories: very-rare, medium-rare, or well-done. Consumers (N = 315) were screened for preference of degree of doneness and fed 4 samples of their preferred doneness (a warm-up and one from each USDA quality grade treatment in a random order). Consumers evaluated steaks on an 8-point verbally anchored hedonic scale for tenderness, juiciness, flavor, and overall like as well as rated steaks as acceptable or unacceptable for all palatability traits. Quality grade had no effect (P > 0.05) on consumer ratings for tenderness, juiciness, flavor, and overall like scores, with all traits averaging above a 7 ("like very much") on the 8-point scale. In addition, no differences (P > 0.05) were found in the percentage of samples rated as acceptable for all palatability traits, with more than 94% of samples rated acceptable for each trait in all quality grades evaluated. Steaks cooked to well-done had lower (P < 0.05) juiciness scores than steaks cooked to very-rare or medium-rare and were rated lower for tenderness (P < 0.05) than steaks cooked to a very-rare degree of doneness. Results indicate consumers were not able to detect differences in tenderness, juiciness, flavor, or overall like among beef tenderloin steaks from USDA Choice and Select quality grades. © 2015 Institute of Food Technologists®

Fixation probability in a two-locus intersexual selection model.

PubMed

Durand, Guillermo; Lessard, Sabin

2016-06-01

We study a two-locus model of intersexual selection in a finite haploid population reproducing according to a discrete-time Moran model with a trait locus expressed in males and a preference locus expressed in females. We show that the probability of ultimate fixation of a single mutant allele for a male ornament introduced at random at the trait locus given any initial frequency state at the preference locus is increased by weak intersexual selection and recombination, weak or strong. Moreover, this probability exceeds the initial frequency of the mutant allele even in the case of a costly male ornament if intersexual selection is not too weak. On the other hand, the probability of ultimate fixation of a single mutant allele for a female preference towards a male ornament introduced at random at the preference locus is increased by weak intersexual selection and weak recombination if the female preference is not costly, and is strong enough in the case of a costly male ornament. The analysis relies on an extension of the ancestral recombination-selection graph for samples of haplotypes to take into account events of intersexual selection, while the symbolic calculation of the fixation probabilities is made possible in a reasonable time by an optimizing algorithm. Copyright © 2016 Elsevier Inc. All rights reserved.

47 CFR 1.1603 - Conduct of random selection.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Conduct of random selection. 1.1603 Section 1.1603 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE Random Selection Procedures for Mass Media Services General Procedures § 1.1603 Conduct of random selection. The...

47 CFR 1.1603 - Conduct of random selection.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Conduct of random selection. 1.1603 Section 1.1603 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE Random Selection Procedures for Mass Media Services General Procedures § 1.1603 Conduct of random selection. The...

Chloroacetanilide herbicide metabolites in Wisconsin groundwater: 2001 survey results.

PubMed

Postle, Jeffrey K; Rheineck, Bruce D; Allen, Paula E; Baldock, Jon O; Cook, Cody J; Zogbaum, Randy; Vandenbrook, James P

2004-10-15

A survey of agricultural chemicals in Wisconsin groundwater was conducted between October 2000 and April 2001 to obtain a current picture of agricultural chemicals in groundwater used for private drinking water. A stratified, random sampling procedure was used to select 336 sampling locations. Water from private drinking water wells randomly selected from within the 336 sampling locations was analyzed for 18 compounds including herbicides, herbicide metabolites, and nitrate. This report focuses on the frequency and concentration of chloroacetanilide herbicides and their metabolites. Analysis of data resulted in an estimated proportion of 38+/-5.0% of wells that contained detectable levels of a herbicide or herbicide metabolite. The most commonly detected compound was alachlor ESA with a proportion estimate of 28+/-4.6%. Other detected compounds in order of prevalence were metolachlor ESA, metolachlor OA, alachlor OA, acetochlor ESA, and parent alachlor. Estimates of the mean concentration for the detects ranged from 0.15+/-0.082 microg/L for acetochlor ESA to 1.8+/-0.60 microg/L for alachlor OA. Water quality standards have not been developed for these chloroacetanilide herbicide metabolites. The results of this survey emphasize the need for toxicological assessments of herbicide metabolite compounds and establishment of water quality standards at the state and federal levels.

Hog Charm II tetracycline test screening results compared with a liquid chromatography tandem mass spectrometry 10-μg/kg method.

PubMed

Salter, Robert; Holmes, Steven; Legg, David; Coble, Joel; George, Bruce

2012-02-01

Pork tissue samples that tested positive and negative by the Charm II tetracycline test screening method in the slaughter plant laboratory were tested with the modified AOAC International liquid chromatography tandem mass spectrometry (LC-MS-MS) method 995.09 to determine the predictive value of the screening method at detecting total tetracyclines at 10 μg/kg of tissue, in compliance with Russian import regulations. There were 218 presumptive-positive tetracycline samples of 4,195 randomly tested hogs. Of these screening test positive samples, 83% (182) were positive, >10 μg/kg by LC-MS-MS; 12.8% (28) were false violative, greater than limit of detection (LOD) but <10 μg/kg; and 4.2% (8) were not detected at the LC-MS-MS LOD. The 36 false-violative and not-detected samples represent 1% of the total samples screened. Twenty-seven of 30 randomly selected tetracycline screening negative samples tested below the LC-MS-MS LOD, and 3 samples tested <3 μg/kg chlortetracycline. Results indicate that the Charm II tetracycline test is effective at predicting hogs containing >10 μg/kg total tetracyclines in compliance with Russian import regulations.

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.

Epidemiological survey of brucellosis in sheep and goats in selected pastoral and agro-pastoral lowlands of Ethiopia.

PubMed

Sintayehu, G; Melesse, B; Abayneh, D; Sintayehu, A; Melaku, S; Alehegne, W; Mesfin, S; De Blas, I; Casal, J; Allepuz, A; Martin-Valls, G; Africa, T; Abera, K

2015-12-01

An epidemiological survey was conducted in pastoral regions of Ethiopia to investigate the distribution of brucellosis in sheep and goats. Between November 2004 and December 2007, a total of 6,201 serum samples were collected from 67 randomly selected peasant associations, 25 districts and eight pastoral zones of Ethiopia. The Rose Bengal plate test (RBPT) and complement fixation test were used in series. Samples for bacteriology were collected from three export abattoirs, where 285 goats were randomly selected and tested by RBPTthree days before slaughter. Tissue samples were collected from 14 strongly positive goats and cultured in dextrose agar and Brucella agar base. To confirm and subtype the isolates, staining, biochemical tests and polymerase chain reaction were used. The overall standardised seroprevalence of brucellosis was 1.9%, ranging from 0.07% in Jijiga zone to 3.3% in Borena zone. There was statistically significant variation among the studied regions, zones, districts and peasant associations (p < 0.05). Male goats and sheep were twice as likely to test positive as females (relative risk [RRJ: 2.04; 95% confidence interval [CI]:1.7-3.4; x2 = 21.05, p < 0.05). Adults (older than 1.5 years) were three times more likely to test positive than younger animals (RR: 2.76; 95% CI: 1.14-6.73; chi2 = 5.18, p < 0.05). Goats were around four times more likely to be infected than sheep (RR: 3.8; 95% CI: 2.4-6.1; chi2 = 36.99, p < 0.05). Brucella melitensis was isolated from 2 of the 14 samples analysed. The widespread distribution of brucellosis in goats and sheep in these areas justifies the use of control measures to minimise the economic losses and public health hazards.

Randomized clinical trials in dentistry: Risks of bias, risks of random errors, reporting quality, and methodologic quality over the years 1955–2013

PubMed Central

Armijo-Olivo, Susan; Cummings, Greta G.; Amin, Maryam; Flores-Mir, Carlos

2017-01-01

Objectives To examine the risks of bias, risks of random errors, reporting quality, and methodological quality of randomized clinical trials of oral health interventions and the development of these aspects over time. Methods We included 540 randomized clinical trials from 64 selected systematic reviews. We extracted, in duplicate, details from each of the selected randomized clinical trials with respect to publication and trial characteristics, reporting and methodologic characteristics, and Cochrane risk of bias domains. We analyzed data using logistic regression and Chi-square statistics. Results Sequence generation was assessed to be inadequate (at unclear or high risk of bias) in 68% (n = 367) of the trials, while allocation concealment was inadequate in the majority of trials (n = 464; 85.9%). Blinding of participants and blinding of the outcome assessment were judged to be inadequate in 28.5% (n = 154) and 40.5% (n = 219) of the trials, respectively. A sample size calculation before the initiation of the study was not performed/reported in 79.1% (n = 427) of the trials, while the sample size was assessed as adequate in only 17.6% (n = 95) of the trials. Two thirds of the trials were not described as double blinded (n = 358; 66.3%), while the method of blinding was appropriate in 53% (n = 286) of the trials. We identified a significant decrease over time (1955–2013) in the proportion of trials assessed as having inadequately addressed methodological quality items (P < 0.05) in 30 out of the 40 quality criteria, or as being inadequate (at high or unclear risk of bias) in five domains of the Cochrane risk of bias tool: sequence generation, allocation concealment, incomplete outcome data, other sources of bias, and overall risk of bias. Conclusions The risks of bias, risks of random errors, reporting quality, and methodological quality of randomized clinical trials of oral health interventions have improved over time; however, further efforts that contribute to the development of more stringent methodology and detailed reporting of trials are still needed. PMID:29272315

Randomized clinical trials in dentistry: Risks of bias, risks of random errors, reporting quality, and methodologic quality over the years 1955-2013.

PubMed

Saltaji, Humam; Armijo-Olivo, Susan; Cummings, Greta G; Amin, Maryam; Flores-Mir, Carlos

2017-01-01

To examine the risks of bias, risks of random errors, reporting quality, and methodological quality of randomized clinical trials of oral health interventions and the development of these aspects over time. We included 540 randomized clinical trials from 64 selected systematic reviews. We extracted, in duplicate, details from each of the selected randomized clinical trials with respect to publication and trial characteristics, reporting and methodologic characteristics, and Cochrane risk of bias domains. We analyzed data using logistic regression and Chi-square statistics. Sequence generation was assessed to be inadequate (at unclear or high risk of bias) in 68% (n = 367) of the trials, while allocation concealment was inadequate in the majority of trials (n = 464; 85.9%). Blinding of participants and blinding of the outcome assessment were judged to be inadequate in 28.5% (n = 154) and 40.5% (n = 219) of the trials, respectively. A sample size calculation before the initiation of the study was not performed/reported in 79.1% (n = 427) of the trials, while the sample size was assessed as adequate in only 17.6% (n = 95) of the trials. Two thirds of the trials were not described as double blinded (n = 358; 66.3%), while the method of blinding was appropriate in 53% (n = 286) of the trials. We identified a significant decrease over time (1955-2013) in the proportion of trials assessed as having inadequately addressed methodological quality items (P < 0.05) in 30 out of the 40 quality criteria, or as being inadequate (at high or unclear risk of bias) in five domains of the Cochrane risk of bias tool: sequence generation, allocation concealment, incomplete outcome data, other sources of bias, and overall risk of bias. The risks of bias, risks of random errors, reporting quality, and methodological quality of randomized clinical trials of oral health interventions have improved over time; however, further efforts that contribute to the development of more stringent methodology and detailed reporting of trials are still needed.

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.

Batch Effect Confounding Leads to Strong Bias in Performance Estimates Obtained by Cross-Validation

PubMed Central

Delorenzi, Mauro

2014-01-01

Background With the large amount of biological data that is currently publicly available, many investigators combine multiple data sets to increase the sample size and potentially also the power of their analyses. However, technical differences (“batch effects”) as well as differences in sample composition between the data sets may significantly affect the ability to draw generalizable conclusions from such studies. Focus The current study focuses on the construction of classifiers, and the use of cross-validation to estimate their performance. In particular, we investigate the impact of batch effects and differences in sample composition between batches on the accuracy of the classification performance estimate obtained via cross-validation. The focus on estimation bias is a main difference compared to previous studies, which have mostly focused on the predictive performance and how it relates to the presence of batch effects. Data We work on simulated data sets. To have realistic intensity distributions, we use real gene expression data as the basis for our simulation. Random samples from this expression matrix are selected and assigned to group 1 (e.g., ‘control’) or group 2 (e.g., ‘treated’). We introduce batch effects and select some features to be differentially expressed between the two groups. We consider several scenarios for our study, most importantly different levels of confounding between groups and batch effects. Methods We focus on well-known classifiers: logistic regression, Support Vector Machines (SVM), k-nearest neighbors (kNN) and Random Forests (RF). Feature selection is performed with the Wilcoxon test or the lasso. Parameter tuning and feature selection, as well as the estimation of the prediction performance of each classifier, is performed within a nested cross-validation scheme. The estimated classification performance is then compared to what is obtained when applying the classifier to independent data. PMID:24967636

Prevalence and pattern of self-medication in Karachi: A community survey

PubMed Central

Afridi, M. Iqbal; Rasool, Ghulam; Tabassum, Rabia; Shaheen, Marriam; Siddiqullah; Shujauddin, M.

2015-01-01

Objective: To study the prevalence and pattern of self-medication among adult males and females in Karachi, Pakistan. Methods: This cross-sectional community- based survey was carried out at five randomly selected towns of Karachi (Defence, Gulshan-e-Iqbal, North Nazimabad, Malir, Orangi town) over a period of 3 months (October, November & December 2012). A sample size of 500 adult cases (250 males & 250 females), with systemic random selection from different towns of Karachi were inducted in this study. The city was divided in 5 zones and one town from each zone was selected by systemic randomization. First available male and female from each randomly selected house were included in the study. After consent and confidentiality assurance they were interviewed on semi-structured Performa designed for this purpose. Results were analyzed and tabulated through SPSS v14.0. Result: The prevalence of self-medication in males and females in Karachi is found to be 84.8% (males 88.4% and females 81.2%). The most frequent symptoms for which self-medication used were headache (32.7%), fever (23.3%) and the medicines used were painkillers (28.8%), fever reducer medicines (19.8%). The most common reason 33.3% was previous experience with similar symptom. Conclusion: Self-medication is highly prevalent (84.8%) in Karachi. It was frequently used for headache followed by fever. Predominantly painkillers, fever reducer and cough syrups were used in the form of tablets and syrups. Main source of medicines for males were friends and for females were relatives. PMID:26649022

Evaluation of Scat Deposition Transects versus Radio Telemetry for Developing a Species Distribution Model for a Rare Desert Carnivore, the Kit Fox.

PubMed

Dempsey, Steven J; Gese, Eric M; Kluever, Bryan M; Lonsinger, Robert C; Waits, Lisette P

2015-01-01

Development and evaluation of noninvasive methods for monitoring species distribution and abundance is a growing area of ecological research. While noninvasive methods have the advantage of reduced risk of negative factors associated with capture, comparisons to methods using more traditional invasive sampling is lacking. Historically kit foxes (Vulpes macrotis) occupied the desert and semi-arid regions of southwestern North America. Once the most abundant carnivore in the Great Basin Desert of Utah, the species is now considered rare. In recent decades, attempts have been made to model the environmental variables influencing kit fox distribution. Using noninvasive scat deposition surveys for determination of kit fox presence, we modeled resource selection functions to predict kit fox distribution using three popular techniques (Maxent, fixed-effects, and mixed-effects generalized linear models) and compared these with similar models developed from invasive sampling (telemetry locations from radio-collared foxes). Resource selection functions were developed using a combination of landscape variables including elevation, slope, aspect, vegetation height, and soil type. All models were tested against subsequent scat collections as a method of model validation. We demonstrate the importance of comparing multiple model types for development of resource selection functions used to predict a species distribution, and evaluating the importance of environmental variables on species distribution. All models we examined showed a large effect of elevation on kit fox presence, followed by slope and vegetation height. However, the invasive sampling method (i.e., radio-telemetry) appeared to be better at determining resource selection, and therefore may be more robust in predicting kit fox distribution. In contrast, the distribution maps created from the noninvasive sampling (i.e., scat transects) were significantly different than the invasive method, thus scat transects may be appropriate when used in an occupancy framework to predict species distribution. We concluded that while scat deposition transects may be useful for monitoring kit fox abundance and possibly occupancy, they do not appear to be appropriate for determining resource selection. On our study area, scat transects were biased to roadways, while data collected using radio-telemetry was dictated by movements of the kit foxes themselves. We recommend that future studies applying noninvasive scat sampling should consider a more robust random sampling design across the landscape (e.g., random transects or more complete road coverage) that would then provide a more accurate and unbiased depiction of resource selection useful to predict kit fox distribution.

Design, objectives, execution and reporting of published open-label extension studies.

PubMed

Megan, Bowers; Pickering, Ruth M; Weatherall, Mark

2012-04-01

Open-label extension (OLE) studies following blinded randomized controlled trials (RCTs) of pharmaceuticals are increasingly being carried out but do not conform to regulatory standards and questions surround the validity of their evidence. OLE studies are usually discussed as a homogenous group, yet substantial differences in study design still meet the definition of an OLE. We describe published papers reporting OLE studies focussing on stated objectives, design, conduct and reporting. A search of Embase and Medline databases for 1996 to July 2008 revealed 268 papers reporting OLE studies that met our eligibility criteria. A random sample of 50 was selected for detailed review. Over 80% of the studies had efficacy stated as an objective. The most common methods of allocation at the start of the OLE were for all RCT participants to switch to one active treatment or for only participants on the new drug to continue, but in three studies all participants were re-randomized at the start of the OLE. Eligibility criteria and other selection factors resulted in on average of 74% of participants in the preceding RCT(s) enrolling in the OLE and only 57% completed it. Published OLE studies do not form a homogenous group with respect to design or retention of participants, and thus the validity of evidence from an OLE should be judged on an individual basis. The term 'open label' suggests bias through lack of blinding, but slippage in relation to the sample randomized in the preceding RCT may be the more important threat to validity. © 2010 Blackwell Publishing Ltd.

Selecting promising treatments in randomized Phase II cancer trials with an active control.

PubMed

Cheung, Ying Kuen

2009-01-01

The primary objective of Phase II cancer trials is to evaluate the potential efficacy of a new regimen in terms of its antitumor activity in a given type of cancer. Due to advances in oncology therapeutics and heterogeneity in the patient population, such evaluation can be interpreted objectively only in the presence of a prospective control group of an active standard treatment. This paper deals with the design problem of Phase II selection trials in which several experimental regimens are compared to an active control, with an objective to identify an experimental arm that is more effective than the control or to declare futility if no such treatment exists. Conducting a multi-arm randomized selection trial is a useful strategy to prioritize experimental treatments for further testing when many candidates are available, but the sample size required in such a trial with an active control could raise feasibility concerns. In this study, we extend the sequential probability ratio test for normal observations to the multi-arm selection setting. The proposed methods, allowing frequent interim monitoring, offer high likelihood of early trial termination, and as such enhance enrollment feasibility. The termination and selection criteria have closed form solutions and are easy to compute with respect to any given set of error constraints. The proposed methods are applied to design a selection trial in which combinations of sorafenib and erlotinib are compared to a control group in patients with non-small-cell lung cancer using a continuous endpoint of change in tumor size. The operating characteristics of the proposed methods are compared to that of a single-stage design via simulations: The sample size requirement is reduced substantially and is feasible at an early stage of drug development.

Do Evidence-Based Youth Psychotherapies Outperform Usual Clinical Care? A Multilevel Meta-Analysis

PubMed Central

Weisz, John R.; Kuppens, Sofie; Eckshtain, Dikla; Ugueto, Ana M.; Hawley, Kristin M.; Jensen-Doss, Amanda

2013-01-01

Context Research across four decades has produced numerous empirically-tested evidence-based psychotherapies (EBPs) for youth psychopathology, developed to improve upon usual clinical interventions. Advocates argue that these should replace usual care; but do the EBPs produce better outcomes than usual care? Objective This question was addressed in a meta-analysis of 52 randomized trials directly comparing EBPs to usual care. Analyses assessed the overall effect of EBPs vs. usual care, and candidate moderators; multilevel analysis was used to address the dependency among effect sizes that is common but typically unaddressed in psychotherapy syntheses. Data Sources The PubMed, PsychINFO, and Dissertation Abstracts International databases were searched for studies from January 1, 1960 – December 31, 2010. Study Selection 507 randomized youth psychotherapy trials were identified. Of these, the 52 studies that compared EBPs to usual care were included in the meta-analysis. Data Extraction Sixteen variables (participant, treatment, and study characteristics) were extracted from each study, and effect sizes were calculated for all EBP versus usual care comparisons. Data Synthesis EBPs outperformed usual care. Mean effect size was 0.29; the probability was 58% that a randomly selected youth receiving an EBP would be better off after treatment than a randomly selected youth receiving usual care. Three variables moderated treatment benefit: Effect sizes decreased for studies conducted outside North America, for studies in which all participants were impaired enough to qualify for diagnoses, and for outcomes reported by people other than the youths and parents in therapy. For certain key groups (e.g., studies using clinically referred samples and diagnosed samples), significant EBP effects were not demonstrated. Conclusions EBPs outperformed usual care, but the EBP advantage was modest and moderated by youth, location, and assessment characteristics. There is room for improvement in EBPs, both in the magnitude and range of their benefit, relative to usual care. PMID:23754332

Four soil orders on a Vermont mountaintop-one-third of the world`s soil orders in a 2500-square-meter research plot

Treesearch

Thomas R. Villars; Scott W. Bailey; Donald S. Ross

2015-01-01

As part of the Vermont Long-Term Soil Monitoring Project, five 50 x 50 m plots were established on protected forestland across Vermont. In 2002, ten randomly selected subplots at each monitoring plot were sampled. The 10 pedons sampled at the high-elevation spruce-fir “Forehead” plot on Mount Mansfield were found to include soils of four taxonomic Orders: Entisols,...

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

On the importance of incorporating sampling weights in ...

EPA Pesticide Factsheets

Occupancy models are used extensively to assess wildlife-habitat associations and to predict species distributions across large geographic regions. Occupancy models were developed as a tool to properly account for imperfect detection of a species. Current guidelines on survey design requirements for occupancy models focus on the number of sample units and the pattern of revisits to a sample unit within a season. We focus on the sampling design or how the sample units are selected in geographic space (e.g., stratified, simple random, unequal probability, etc). In a probability design, each sample unit has a sample weight which quantifies the number of sample units it represents in the finite (oftentimes areal) sampling frame. We demonstrate the importance of including sampling weights in occupancy model estimation when the design is not a simple random sample or equal probability design. We assume a finite areal sampling frame as proposed for a national bat monitoring program. We compare several unequal and equal probability designs and varying sampling intensity within a simulation study. We found the traditional single season occupancy model produced biased estimates of occupancy and lower confidence interval coverage rates compared to occupancy models that accounted for the sampling design. We also discuss how our findings inform the analyses proposed for the nascent North American Bat Monitoring Program and other collaborative synthesis efforts that propose h

Maximizing the reliability of genomic selection by optimizing the calibration set of reference individuals: comparison of methods in two diverse groups of maize inbreds (Zea mays L.).

PubMed

Rincent, R; Laloë, D; Nicolas, S; Altmann, T; Brunel, D; Revilla, P; Rodríguez, V M; Moreno-Gonzalez, J; Melchinger, A; Bauer, E; Schoen, C-C; Meyer, N; Giauffret, C; Bauland, C; Jamin, P; Laborde, J; Monod, H; Flament, P; Charcosset, A; Moreau, L

2012-10-01

Genomic selection refers to the use of genotypic information for predicting breeding values of selection candidates. A prediction formula is calibrated with the genotypes and phenotypes of reference individuals constituting the calibration set. The size and the composition of this set are essential parameters affecting the prediction reliabilities. The objective of this study was to maximize reliabilities by optimizing the calibration set. Different criteria based on the diversity or on the prediction error variance (PEV) derived from the realized additive relationship matrix-best linear unbiased predictions model (RA-BLUP) were used to select the reference individuals. For the latter, we considered the mean of the PEV of the contrasts between each selection candidate and the mean of the population (PEVmean) and the mean of the expected reliabilities of the same contrasts (CDmean). These criteria were tested with phenotypic data collected on two diversity panels of maize (Zea mays L.) genotyped with a 50k SNPs array. In the two panels, samples chosen based on CDmean gave higher reliabilities than random samples for various calibration set sizes. CDmean also appeared superior to PEVmean, which can be explained by the fact that it takes into account the reduction of variance due to the relatedness between individuals. Selected samples were close to optimality for a wide range of trait heritabilities, which suggests that the strategy presented here can efficiently sample subsets in panels of inbred lines. A script to optimize reference samples based on CDmean is available on request.

Signal processor for processing ultrasonic receiver signals

DOEpatents

Fasching, George E.

1980-01-01

A signal processor is provided which uses an analog integrating circuit in conjunction with a set of digital counters controlled by a precision clock for sampling timing to provide an improved presentation of an ultrasonic transmitter/receiver signal. The signal is sampled relative to the transmitter trigger signal timing at precise times, the selected number of samples are integrated and the integrated samples are transferred and held for recording on a strip chart recorder or converted to digital form for storage. By integrating multiple samples taken at precisely the same time with respect to the trigger for the ultrasonic transmitter, random noise, which is contained in the ultrasonic receiver signal, is reduced relative to the desired useful signal.

Ceramic Technology for Advanced Heat Engines Project Semiannual Progress Report for Period October 1985 Through March 1986

DTIC Science & Technology

1986-08-01

materials (2.2 w/o and 3.0 w/o MgO). The other two batches (2.8 w/o and 3.1 w/o MgO), of higher purity, were made using E-10 zirconia powder from...CID) powders Two methods have been used for the coprecipitation of doped zirconia powders from solutions of chemical precursors. (4) Method I, for...of powder, approximate sample size 3.2 Kg (6.4 Kg for zirconia powder ); 342 3. Random selection of sample; 4. Partial drying of sample to reduce caking

Fluorescence Excitation Spectroscopy for Phytoplankton Species Classification Using an All-Pairs Method: Characterization of a System with Unexpectedly Low Rank.

PubMed

Rekully, Cameron M; Faulkner, Stefan T; Lachenmyer, Eric M; Cunningham, Brady R; Shaw, Timothy J; Richardson, Tammi L; Myrick, Michael L

2018-03-01

An all-pairs method is used to analyze phytoplankton fluorescence excitation spectra. An initial set of nine phytoplankton species is analyzed in pairwise fashion to select two optical filter sets, and then the two filter sets are used to explore variations among a total of 31 species in a single-cell fluorescence imaging photometer. Results are presented in terms of pair analyses; we report that 411 of the 465 possible pairings of the larger group of 31 species can be distinguished using the initial nine-species-based selection of optical filters. A bootstrap analysis based on the larger data set shows that the distribution of possible pair separation results based on a randomly selected nine-species initial calibration set is strongly peaked in the 410-415 pair separation range, consistent with our experimental result. Further, the result for filter selection using all 31 species is also 411 pair separations; The set of phytoplankton fluorescence excitation spectra is intuitively high in rank due to the number and variety of pigments that contribute to the spectrum. However, the results in this report are consistent with an effective rank as determined by a variety of heuristic and statistical methods in the range of 2-3. These results are reviewed in consideration of how consistent the filter selections are from model to model for the data presented here. We discuss the common observation that rank is generally found to be relatively low even in many seemingly complex circumstances, so that it may be productive to assume a low rank from the beginning. If a low-rank hypothesis is valid, then relatively few samples are needed to explore an experimental space. Under very restricted circumstances for uniformly distributed samples, the minimum number for an initial analysis might be as low as 8-11 random samples for 1-3 factors.

Comparison of Address-based Sampling and Random-digit Dialing Methods for Recruiting Young Men as Controls in a Case-Control Study of Testicular Cancer Susceptibility

PubMed Central

Clagett, Bartholt; Nathanson, Katherine L.; Ciosek, Stephanie L.; McDermoth, Monique; Vaughn, David J.; Mitra, Nandita; Weiss, Andrew; Martonik, Rachel; Kanetsky, Peter A.

2013-01-01

Random-digit dialing (RDD) using landline telephone numbers is the historical gold standard for control recruitment in population-based epidemiologic research. However, increasing cell-phone usage and diminishing response rates suggest that the effectiveness of RDD in recruiting a random sample of the general population, particularly for younger target populations, is decreasing. In this study, we compared landline RDD with alternative methods of control recruitment, including RDD using cell-phone numbers and address-based sampling (ABS), to recruit primarily white men aged 18–55 years into a study of testicular cancer susceptibility conducted in the Philadelphia, Pennsylvania, metropolitan area between 2009 and 2012. With few exceptions, eligible and enrolled controls recruited by means of RDD and ABS were similar with regard to characteristics for which data were collected on the screening survey. While we find ABS to be a comparably effective method of recruiting young males compared with landline RDD, we acknowledge the potential impact that selection bias may have had on our results because of poor overall response rates, which ranged from 11.4% for landline RDD to 1.7% for ABS. PMID:24008901

Assessing the performance of multiplexed tandem PCR for the diagnosis of pathogenic genotypes of Theileria orientalis using pooled blood samples from cattle.

PubMed

Gebrekidan, Hagos; Gasser, Robin B; Stevenson, Mark A; McGrath, Sean; Jabbar, Abdul

2017-02-01

Oriental theileriosis caused by multiple genotypes of Theileria orientalis is an important tick-borne disease of bovines. Here, we assessed the performance of an established multiplexed tandem PCR (MT-PCR) for the diagnosis of the two recognized, pathogenic genotypes (chitose and ikeda) of T. orientalis in cattle using pooled blood samples. We used a total of 265 cattle blood samples, which were divided into two groups according to previous MT-PCR results for individual samples. Samples in group 1 (n = 155) were from a herd with a relatively high prevalence of T. orientalis infection; and those in group 2 (n = 110) were from four herds with a low prevalence. For group 1, 31 and 15 batches of five- and ten-pooled samples (selected at random), respectively, were formed. For group 2, 22 and 11 batches of five- and ten-pooled samples (selected at random), respectively, were formed. DNAs from individual pooled samples in each batch and group were then tested by MT-PCR. For group 1, the apparent prevalences estimated using the 31 batches of five-pooled samples (97%) and 15 batches of ten-pooled samples (100%) were significantly higher compared with individual samples (75%). For group 2, higher apparent prevalences (9% and 36%) were also recorded for the 22 and 11 batches of pooled samples, respectively, compared with individual samples (7%). Overall, the average infection intensity recorded for the genotypes of chitose and ikeda were considerably lower in pooled compared with individual samples. The diagnostic specificities of MT-PCR were estimated at 95% and 94%, respectively, when batches of five- and ten-pooled samples were tested, and 94% for individual samples. The diagnostic sensitivity of this assay was estimated at 98% same for all individual, five- and ten-pooled samples. This study shows that screening batches of five- and ten-pooled blood samples from cattle herds are similar to those obtained for individual samples, and, importantly, that the reduced cost for the testing of pooled samples represents a considerable saving to herd managers. Copyright © 2016 Elsevier Ltd. All rights reserved.

Composing Music with Complex Networks

NASA Astrophysics Data System (ADS)

Liu, Xiaofan; Tse, Chi K.; Small, Michael

In this paper we study the network structure in music and attempt to compose music artificially. Networks are constructed with nodes and edges corresponding to musical notes and their co-occurrences. We analyze sample compositions from Bach, Mozart, Chopin, as well as other types of music including Chinese pop music. We observe remarkably similar properties in all networks constructed from the selected compositions. Power-law exponents of degree distributions, mean degrees, clustering coefficients, mean geodesic distances, etc. are reported. With the network constructed, music can be created by using a biased random walk algorithm, which begins with a randomly chosen note and selects the subsequent notes according to a simple set of rules that compares the weights of the edges, weights of the nodes, and/or the degrees of nodes. The newly created music from complex networks will be played in the presentation.

Investigating Organizational Alienation Behavior in Terms of Some Variables

ERIC Educational Resources Information Center

Dagli, Abidin; Averbek, Emel

2017-01-01

The aim of this study is to detect the perceptions of public primary school teachers regarding organizational alienation behaviors in terms of some variables (gender, marital status and seniority). Survey model was used in this study. The research sample consists of randomly selected 346 teachers from 40 schools in the central district of Mardin,…

An Examination of Ohio Principals' Attitudes toward Technology and First Amendment Law: Implications for Leadership

ERIC Educational Resources Information Center

Gooden, Mark A.

2012-01-01

Principals have acknowledged the challenges with remaining current on issues in the law. A unique challenge for principals is the intersection of students' First Amendment rights in the school context and the legal issues surrounding student-created webpages. Using a randomly selected sample of Ohio high school secondary principals, I investigated…

Motor Carrier Drug And Alcohol Violations: Comparison Of Compliance Review Data From SafeStat Selected Carriers And A Random Sample Of Carriers

DOT National Transportation Integrated Search

2000-10-01

There has been interest in the extent to which motor carriers are in compliance with Part 382 of the Federal Motor Carrier Safety Regulations (Controlled Substances and Alcohol Use Testing), as well as the extent to which the Federal Motor Carrier Sa...