An Investigation of the Sample Performance of Two Nonnormality Corrections for RMSEA
ERIC Educational Resources Information Center
Brosseau-Liard, Patricia E.; Savalei, Victoria; Li, Libo
2012-01-01
The root mean square error of approximation (RMSEA) is a popular fit index in structural equation modeling (SEM). Typically, RMSEA is computed using the normal theory maximum likelihood (ML) fit function. Under nonnormality, the uncorrected sample estimate of the ML RMSEA tends to be inflated. Two robust corrections to the sample ML RMSEA have…
ERIC Educational Resources Information Center
Huberty, Carl J.
An approach to statistical testing, which combines Neyman-Pearson hypothesis testing and Fisher significance testing, is recommended. The use of P-values in this approach is discussed in some detail. The author also discusses some problems which are often found in introductory statistics textbooks. The problems involve the definitions of…
Pilot Class Testing: Statistics.
ERIC Educational Resources Information Center
Washington Univ., Seattle. Washington Foreign Language Program.
Statistics derived from test score data from the pilot classes participating in the Washington Foreign Language Program are presented in tables in this report. An index accompanies the tables, itemizing the classes by level (FLES, middle, and high school), grade test, language skill, and school. MLA-Coop test performances for each class were…
Statistical Significance Testing.
ERIC Educational Resources Information Center
McLean, James E., Ed.; Kaufman, Alan S., Ed.
1998-01-01
The controversy about the use or misuse of statistical significance testing has become the major methodological issue in educational research. This special issue contains three articles that explore the controversy, three commentaries on these articles, an overall response, and three rejoinders by the first three authors. They are: (1)…
Monroe, Scott; Cai, Li
2015-01-01
This research is concerned with two topics in assessing model fit for categorical data analysis. The first topic involves the application of a limited-information overall test, introduced in the item response theory literature, to structural equation modeling (SEM) of categorical outcome variables. Most popular SEM test statistics assess how well the model reproduces estimated polychoric correlations. In contrast, limited-information test statistics assess how well the underlying categorical data are reproduced. Here, the recently introduced C2 statistic of Cai and Monroe (2014) is applied. The second topic concerns how the root mean square error of approximation (RMSEA) fit index can be affected by the number of categories in the outcome variable. This relationship creates challenges for interpreting RMSEA. While the two topics initially appear unrelated, they may conveniently be studied in tandem since RMSEA is based on an overall test statistic, such as C2. The results are illustrated with an empirical application to data from a large-scale educational survey.
Fit Indices Versus Test Statistics
ERIC Educational Resources Information Center
Yuan, Ke-Hai
2005-01-01
Model evaluation is one of the most important aspects of structural equation modeling (SEM). Many model fit indices have been developed. It is not an exaggeration to say that nearly every publication using the SEM methodology has reported at least one fit index. Most fit indices are defined through test statistics. Studies and interpretation of…
Statistics and Hypothesis Testing in Biology.
ERIC Educational Resources Information Center
Maret, Timothy J.; Ziemba, Robert E.
1997-01-01
Suggests that early in their education students be taught to use basic statistical tests as rigorous methods of comparing experimental results with scientific hypotheses. Stresses that students learn how to use statistical tests in hypothesis-testing by applying them in actual hypothesis-testing situations. To illustrate, uses questions such as…
Quantum Statistical Testing of a QRNG Algorithm
Humble, Travis S; Pooser, Raphael C; Britt, Keith A
2013-01-01
We present the algorithmic design of a quantum random number generator, the subsequent synthesis of a physical design and its verification using quantum statistical testing. We also describe how quantum statistical testing can be used to diagnose channel noise in QKD protocols.
2009 GED Testing Program Statistical Report
ERIC Educational Resources Information Center
GED Testing Service, 2010
2010-01-01
The "2009 GED[R] Testing Program Statistical Report" is the 52nd annual report in the program's 68-year history of providing a second opportunity for adults without a high school credential to earn their jurisdiction's GED credential. The report provides candidate demographic and GED Test performance statistics as well as historical information on…
The insignificance of statistical significance testing
Johnson, Douglas H.
1999-01-01
Despite their use in scientific joumals such asThe journal of Wildlife Management, statistical hypothesis tests add very little value to the products of research. Indeed, they frequently confuse the interpretation of data. This paper describes how statistical hypothesis tests are often viewed, and then contrasts that interpretation with the correct one. I discuss the arbitrariness of P-values, conclusions that the null hypothesis is true, power analysis, and distinctions between statistical and biological significance. Statistical hypothesis testing, in which the null hypothesis about the properties of a population is almost always known a priori to be false, is contrasted with scientific hypothesis testing, which examines a credible null hypothesis about phenomena in nature. More meaningful alternatives are briefly outlined, including estimation and confidence intervals for determining the importance of factors, decision theory for guiding actions in the face of uncertainty, and Bayesian approaches to hypothesis testing and other statistical practices.
Applications of Statistical Tests in Hand Surgery
Song, Jae W.; Haas, Ann; Chung, Kevin C.
2015-01-01
During the nineteenth century, with the emergence of public health as a goal to improve hygiene and conditions of the poor, statistics established itself as a distinct scientific field important for critically interpreting studies of public health concerns. During the twentieth century, statistics began to evolve mathematically and methodologically with hypothesis testing and experimental design. Today, the design of medical experiments centers around clinical trials and observational studies, and with the use of statistics, the collected data are summarized, weighed, and presented to direct both physicians and the public towards Evidence-Based Medicine. Having a basic understanding of statistics is mandatory in evaluating the validity of published literature and applying it to patient care. In this review, we aim to apply a practical approach in discussing basic statistical tests by providing a guide to choosing the correct statistical test along with examples relevant to hand surgery research. PMID:19969193
T test as a parametric statistic.
Kim, Tae Kyun
2015-12-01
In statistic tests, the probability distribution of the statistics is important. When samples are drawn from population N (µ, σ(2)) with a sample size of n, the distribution of the sample mean X̄ should be a normal distribution N (µ, σ(2)/n). Under the null hypothesis µ = µ0, the distribution of statistics [Formula: see text] should be standardized as a normal distribution. When the variance of the population is not known, replacement with the sample variance s (2) is possible. In this case, the statistics [Formula: see text] follows a t distribution (n-1 degrees of freedom). An independent-group t test can be carried out for a comparison of means between two independent groups, with a paired t test for paired data. As the t test is a parametric test, samples should meet certain preconditions, such as normality, equal variances and independence.
Teaching Statistics in Language Testing Courses
ERIC Educational Resources Information Center
Brown, James Dean
2013-01-01
The purpose of this article is to examine the literature on teaching statistics for useful ideas that teachers of language testing courses can draw on and incorporate into their teaching toolkits as they see fit. To those ends, the article addresses eight questions: What is known generally about teaching statistics? Why are students so anxious…
Statistics Test Questions: Content and Trends
ERIC Educational Resources Information Center
Salcedo, Audy
2014-01-01
This study presents the results of the analysis of a group of teacher-made test questions for statistics courses at the university level. Teachers were asked to submit tests they had used in their previous two semesters. Ninety-seven tests containing 978 questions were gathered and classified according to the SOLO taxonomy (Biggs & Collis,…
Binomial test statistics using Psi functions
Bowman, Kimiko o
2007-01-01
For the negative binomial model (probability generating function (p + 1 - pt){sup -k}) a logarithmic derivative is the Psi function difference {psi}(k + x) - {psi}(k); this and its derivatives lead to a test statistic to decide on the validity of a specified model. The test statistic uses a data base so there exists a comparison available between theory and application. Note that the test function is not dominated by outliers. Applications to (i) Fisher's tick data, (ii) accidents data, (iii) Weldon's dice data are included.
Accurate statistical tests for smooth classification images.
Chauvin, Alan; Worsley, Keith J; Schyns, Philippe G; Arguin, Martin; Gosselin, Frédéric
2005-10-05
Despite an obvious demand for a variety of statistical tests adapted to classification images, few have been proposed. We argue that two statistical tests based on random field theory (RFT) satisfy this need for smooth classification images. We illustrate these tests on classification images representative of the literature from F. Gosselin and P. G. Schyns (2001) and from A. B. Sekuler, C. M. Gaspar, J. M. Gold, and P. J. Bennett (2004). The necessary computations are performed using the Stat4Ci Matlab toolbox.
2006 GED Testing Program Statistical Report
ERIC Educational Resources Information Center
GED Testing Service, 2007
2007-01-01
The 2006 GED[R] Testing Program Statistical Report is the 49th annual report in the program's 65-year history of providing a second opportunity to adults without a high school diploma to earn their jurisdiction's General Educational Development (GED) credential, and, as a result, advance their educational, personal, and professional aspirations.…
2007 GED Testing Program Statistical Report
ERIC Educational Resources Information Center
GED Testing Service, 2008
2008-01-01
The "2007 GED[R] Testing Program Statistical Report" is the 50th annual report in the program's 66-year history of providing a second opportunity for adults without a high school diploma to earn their jurisdiction's GED credential, and, as a result, advance their educational, personal, and professional aspirations. Section I, "Who Lacks a High…
Comments on the Statistical Significance Testing Articles.
ERIC Educational Resources Information Center
Knapp, Thomas R.
1998-01-01
Expresses a "middle-of-the-road" position on statistical significance testing, suggesting that it has its place but that confidence intervals are generally more useful. Identifies 10 errors of omission or commission in the papers reviewed that weaken the positions taken in their discussions. (SLD)
Mechanical Impact Testing: A Statistical Measurement
NASA Technical Reports Server (NTRS)
Engel, Carl D.; Herald, Stephen D.; Davis, S. Eddie
2005-01-01
In the decades since the 1950s, when NASA first developed mechanical impact testing of materials, researchers have continued efforts to gain a better understanding of the chemical, mechanical, and thermodynamic nature of the phenomenon. The impact mechanism is a real combustion ignition mechanism that needs understanding in the design of an oxygen system. The use of test data from this test method has been questioned due to lack of a clear method of application of the data and variability found between tests, material batches, and facilities. This effort explores a large database that has accumulated over a number of years and explores its overall nature. Moreover, testing was performed to determine the statistical nature of the test procedure to help establish sample size guidelines for material characterization. The current method of determining a pass/fail criterion based on either light emission or sound report or material charring is questioned.
Two statistical tests for meiotic breakpoint analysis.
Plaetke, R; Schachtel, G A
1995-01-01
Meiotic breakpoint analysis (BPA), a statistical method for ordering genetic markers, is increasing in importance as a method for building genetic maps of human chromosomes. Although BPA does not provide estimates of genetic distances between markers, it efficiently locates new markers on already defined dense maps, when likelihood analysis becomes cumbersome or the sample size is small. However, until now no assessments of statistical significance have been available for evaluating the possibility that the results of a BPA were produced by chance. In this paper, we propose two statistical tests to determine whether the size of a sample and its genetic information content are sufficient to distinguish between "no linkage" and "linkage" of a marker mapped by BPA to a certain region. Both tests are exact and should be conducted after a BPA has assigned the marker to an interval on the map. Applications of the new tests are demonstrated by three examples: (1) a synthetic data set, (2) a data set of five markers on human chromosome 8p, and (3) a data set of four markers on human chromosome 17q. PMID:7847387
Statistical tests for prediction of lignite quality
C.J. Kolovos
2007-06-15
Domestic lignite from large, bucket wheel excavators based open pit mines is the main fuel for electricity generation in Greece. Lignite from one or more mines may arrive at any power plant stockyard. The mixture obtained constitutes the lignite fuel fed to the power plant. The fuel is sampled in regular time intervals. These samples are considered as results of observations of values of spatial random variables. The aim was to form and statistically test many small sample populations. Statistical tests on the values of the humidity content, the ash-water free content, and the lower heating value of the lignite fuel indicated that the sample values form a normal population. The Kolmogorov-Smirnov test was applied for testing goodness-of-fit of sample distribution for a three year period and different power plants of the Kozani-Ptolemais area, western Macedonia, Greece. The normal distribution hypothesis can be widely accepted for forecasting the distribution of values of the basic quality characteristics even for a small number of samples.
A Statistical Perspective on Highly Accelerated Testing.
Thomas, Edward V.
2015-02-01
Highly accelerated life testing has been heavily promoted at Sandia (and elsewhere) as a means to rapidly identify product weaknesses caused by flaws in the product's design or manufacturing process. During product development, a small number of units are forced to fail at high stress. The failed units are then examined to determine the root causes of failure. The identification of the root causes of product failures exposed by highly accelerated life testing can instigate changes to the product's design and/or manufacturing process that result in a product with increased reliability. It is widely viewed that this qualitative use of highly accelerated life testing (often associated with the acronym HALT) can be useful. However, highly accelerated life testing has also been proposed as a quantitative means for "demonstrating" the reliability of a product where unreliability is associated with loss of margin via an identified and dominating failure mechanism. It is assumed that the dominant failure mechanism can be accelerated by changing the level of a stress factor that is assumed to be related to the dominant failure mode. In extreme cases, a minimal number of units (often from a pre-production lot) are subjected to a single highly accelerated stress relative to normal use. If no (or, sufficiently few) units fail at this high stress level, some might claim that a certain level of reliability has been demonstrated (relative to normal use conditions). Underlying this claim are assumptions regarding the level of knowledge associated with the relationship between the stress level and the probability of failure. The primary purpose of this document is to discuss (from a statistical perspective) the efficacy of using accelerated life testing protocols (and, in particular, "highly accelerated" protocols) to make quantitative inferences concerning the performance of a product (e.g., reliability) when in fact there is lack-of-knowledge and uncertainty concerning the
Explorations in Statistics: Hypothesis Tests and P Values
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2009-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This second installment of "Explorations in Statistics" delves into test statistics and P values, two concepts fundamental to the test of a scientific null hypothesis. The essence of a test statistic is that it compares what…
SANABRIA, FEDERICO; KILLEEN, PETER R.
2008-01-01
Despite being under challenge for the past 50 years, null hypothesis significance testing (NHST) remains dominant in the scientific field for want of viable alternatives. NHST, along with its significance level p, is inadequate for most of the uses to which it is put, a flaw that is of particular interest to educational practitioners who too often must use it to sanctify their research. In this article, we review the failure of NHST and propose prep, the probability of replicating an effect, as a more useful statistic for evaluating research and aiding practical decision making. PMID:19122766
Statistical analysis of regulatory ecotoxicity tests.
Isnard, P; Flammarion, P; Roman, G; Babut, M; Bastien, P; Bintein, S; Esserméant, L; Férard, J F; Gallotti-Schmitt, S; Saouter, E; Saroli, M; Thiébaud, H; Tomassone, R; Vindimian, E
2001-11-01
ANOVA-type data analysis, i.e.. determination of lowest-observed-effect concentrations (LOECs), and no-observed-effect concentrations (NOECs), has been widely used for statistical analysis of chronic ecotoxicity data. However, it is more and more criticised for several reasons, among which the most important is probably the fact that the NOEC depends on the choice of test concentrations and number of replications and rewards poor experiments, i.e., high variability, with high NOEC values. Thus, a recent OECD workshop concluded that the use of the NOEC should be phased out and that a regression-based estimation procedure should be used. Following this workshop, a working group was established at the French level between government, academia and industry representatives. Twenty-seven sets of chronic data (algae, daphnia, fish) were collected and analysed by ANOVA and regression procedures. Several regression models were compared and relations between NOECs and ECx, for different values of x, were established in order to find an alternative summary parameter to the NOEC. Biological arguments are scarce to help in defining a negligible level of effect x for the ECx. With regard to their use in the risk assessment procedures, a convenient methodology would be to choose x so that ECx are on average similar to the present NOEC. This would lead to no major change in the risk assessment procedure. However, experimental data show that the ECx depend on the regression models and that their accuracy decreases in the low effect zone. This disadvantage could probably be reduced by adapting existing experimental protocols but it could mean more experimental effort and higher cost. ECx (derived with existing test guidelines, e.g., regarding the number of replicates) whose lowest bounds of the confidence interval are on average similar to present NOEC would improve this approach by a priori encouraging more precise experiments. However, narrow confidence intervals are not only
Assessing Statistical Aspects of Test Fairness with Structural Equation Modelling
ERIC Educational Resources Information Center
Kline, Rex B.
2013-01-01
Test fairness and test bias are not synonymous concepts. Test bias refers to statistical evidence that the psychometrics or interpretation of test scores depend on group membership, such as gender or race, when such differences are not expected. A test that is grossly biased may be judged to be unfair, but test fairness concerns the broader, more…
A Note on Measurement Scales and Statistical Testing
ERIC Educational Resources Information Center
Meijer, Rob R.; Oosterloo, Sebie J.
2008-01-01
In elementary books on applied statistics (e.g., Siegel, 1988; Agresti, 1990) and books on research methodology in psychology and personality assessment (e.g., Aiken, 1999), it is often suggested that the choice of a statistical test and the choice of statistical operations should be determined by the level of measurement of the data. Although…
Misuse of statistical test in three decades of psychotherapy research.
Dar, R; Serlin, R C; Omer, H
1994-02-01
This article reviews the misuse of statistical tests in psychotherapy research studies published in the Journal of Consulting and Clinical Psychology in the years 1967-1968, 1977-1978, and 1987-1988. It focuses on 3 major problems in statistical practice: inappropriate uses of null hypothesis tests and p values, neglect of effect size, and inflation of Type I error rate. The impressive frequency of these problems is documented, and changes in statistical practices over the past 3 decades are interpreted in light of trends in psychotherapy research. The article concludes with practical suggestions for rational application of statistical tests.
Testing the Difference of Correlated Agreement Coefficients for Statistical Significance
ERIC Educational Resources Information Center
Gwet, Kilem L.
2016-01-01
This article addresses the problem of testing the difference between two correlated agreement coefficients for statistical significance. A number of authors have proposed methods for testing the difference between two correlated kappa coefficients, which require either the use of resampling methods or the use of advanced statistical modeling…
A Comparison of Statistical Significance Tests for Selecting Equating Functions
ERIC Educational Resources Information Center
Moses, Tim
2009-01-01
This study compared the accuracies of nine previously proposed statistical significance tests for selecting identity, linear, and equipercentile equating functions in an equivalent groups equating design. The strategies included likelihood ratio tests for the loglinear models of tests' frequency distributions, regression tests, Kolmogorov-Smirnov…
Statistical Evaluation of Small-scale Explosives Testing
NASA Astrophysics Data System (ADS)
Guymon, Clint
2013-06-01
Small-scale explosives sensitivity testing is used to qualitatively and quantitatively evaluate risk. Both relative comparison and characterization of the transition from no reaction to reaction is used to estimate that risk. Statistical comparisons and use of statistically efficient methods are critical to accurately and efficiently make risk related decisions. Many public and private entities are not making accurate decisions based on the test data because of the lack of properly applying basic statistical principles. We present methods and examples showing how to use statistics to accurately and efficiently evaluate the risk for relative comparison and in-process risk evaluation. Some of the methods presented include the Significance Chart Method and adaptive step-size techniques like the Neyer D-Optimal method. These methods are compared to the more traditional approaches like Bruceton and Probit. Use of statistical methods can significantly improve the efficiency, accuracy, and applicability of small-scale explosives sensitivity testing.
The Use of Meta-Analytic Statistical Significance Testing
ERIC Educational Resources Information Center
Polanin, Joshua R.; Pigott, Terri D.
2015-01-01
Meta-analysis multiplicity, the concept of conducting multiple tests of statistical significance within one review, is an underdeveloped literature. We address this issue by considering how Type I errors can impact meta-analytic results, suggest how statistical power may be affected through the use of multiplicity corrections, and propose how…
The Importance of Teaching Power in Statistical Hypothesis Testing
ERIC Educational Resources Information Center
Olinsky, Alan; Schumacher, Phyllis; Quinn, John
2012-01-01
In this paper, we discuss the importance of teaching power considerations in statistical hypothesis testing. Statistical power analysis determines the ability of a study to detect a meaningful effect size, where the effect size is the difference between the hypothesized value of the population parameter under the null hypothesis and the true value…
Advances in Testing the Statistical Significance of Mediation Effects
ERIC Educational Resources Information Center
Mallinckrodt, Brent; Abraham, W. Todd; Wei, Meifen; Russell, Daniel W.
2006-01-01
P. A. Frazier, A. P. Tix, and K. E. Barron (2004) highlighted a normal theory method popularized by R. M. Baron and D. A. Kenny (1986) for testing the statistical significance of indirect effects (i.e., mediator variables) in multiple regression contexts. However, simulation studies suggest that this method lacks statistical power relative to some…
BIAZA statistics guidelines: toward a common application of statistical tests for zoo research.
Plowman, Amy B
2008-05-01
Zoo research presents many statistical challenges, mostly arising from the need to work with small sample sizes. Efforts to overcome these often lead to the misuse of statistics including pseudoreplication, inappropriate pooling, assumption violation or excessive Type II errors because of using tests with low power to avoid assumption violation. To tackle these issues and make some general statistical recommendations for zoo researchers, the Research Group of the British and Irish Association of Zoos and Aquariums (BIAZA) conducted a workshop. Participants included zoo-based researchers, university academics with zoo interests and three statistical experts. The result was a BIAZA publication Zoo Research Guidelines: Statistics for Typical Zoo Datasets (Plowman [2006] Zoo research guidelines: statistics for zoo datasets. London: BIAZA), which provides advice for zoo researchers on study design and analysis to ensure appropriate and rigorous use of statistics. The main recommendations are: (1) that many typical zoo investigations should be conducted as single case/small N randomized designs, analyzed with randomization tests, (2) that when comparing complete time budgets across conditions in behavioral studies, G tests and their derivatives are the most appropriate statistical tests and (3) that in studies involving multiple dependent and independent variables there are usually no satisfactory alternatives to traditional parametric tests and, despite some assumption violations, it is better to use these tests with careful interpretation, than to lose information through not testing at all. The BIAZA guidelines were recommended by American Association of Zoos and Aquariums (AZA) researchers at the AZA Annual Conference in Tampa, FL, September 2006, and are free to download from www.biaza.org.uk.
BIAZA statistics guidelines: toward a common application of statistical tests for zoo research.
Plowman, Amy B
2008-05-01
Zoo research presents many statistical challenges, mostly arising from the need to work with small sample sizes. Efforts to overcome these often lead to the misuse of statistics including pseudoreplication, inappropriate pooling, assumption violation or excessive Type II errors because of using tests with low power to avoid assumption violation. To tackle these issues and make some general statistical recommendations for zoo researchers, the Research Group of the British and Irish Association of Zoos and Aquariums (BIAZA) conducted a workshop. Participants included zoo-based researchers, university academics with zoo interests and three statistical experts. The result was a BIAZA publication Zoo Research Guidelines: Statistics for Typical Zoo Datasets (Plowman [2006] Zoo research guidelines: statistics for zoo datasets. London: BIAZA), which provides advice for zoo researchers on study design and analysis to ensure appropriate and rigorous use of statistics. The main recommendations are: (1) that many typical zoo investigations should be conducted as single case/small N randomized designs, analyzed with randomization tests, (2) that when comparing complete time budgets across conditions in behavioral studies, G tests and their derivatives are the most appropriate statistical tests and (3) that in studies involving multiple dependent and independent variables there are usually no satisfactory alternatives to traditional parametric tests and, despite some assumption violations, it is better to use these tests with careful interpretation, than to lose information through not testing at all. The BIAZA guidelines were recommended by American Association of Zoos and Aquariums (AZA) researchers at the AZA Annual Conference in Tampa, FL, September 2006, and are free to download from www.biaza.org.uk. PMID:19360620
Bootstrapping Selected Item Statistics from a Student-Made Test.
ERIC Educational Resources Information Center
Burroughs, Monte
This study applied nonparametric bootstrapping to test null hypotheses for selected statistics (KR-20, difficulty, and discrimination) derived from a student-made test. The test, administered to 21 students enrolled in a graduate-level educational assessment class, contained 42 items, 33 of which were analyzed. Random permutations of the data…
ERIC Educational Resources Information Center
Sanabria, Federico; Killeen, Peter R.
2007-01-01
Despite being under challenge for the past 50 years, null hypothesis significance testing (NHST) remains dominant in the scientific field for want of viable alternatives. NHST, along with its significance level "p," is inadequate for most of the uses to which it is put, a flaw that is of particular interest to educational practitioners who too…
Ganju, Jitendra; Yu, Xinxin; Ma, Guoguang Julie
2013-01-01
Formal inference in randomized clinical trials is based on controlling the type I error rate associated with a single pre-specified statistic. The deficiency of using just one method of analysis is that it depends on assumptions that may not be met. For robust inference, we propose pre-specifying multiple test statistics and relying on the minimum p-value for testing the null hypothesis of no treatment effect. The null hypothesis associated with the various test statistics is that the treatment groups are indistinguishable. The critical value for hypothesis testing comes from permutation distributions. Rejection of the null hypothesis when the smallest p-value is less than the critical value controls the type I error rate at its designated value. Even if one of the candidate test statistics has low power, the adverse effect on the power of the minimum p-value statistic is not much. Its use is illustrated with examples. We conclude that it is better to rely on the minimum p-value rather than a single statistic particularly when that single statistic is the logrank test, because of the cost and complexity of many survival trials.
ERIC Educational Resources Information Center
Hong, Eunsook
A path analytic model of state test anxiety was tested in 169 college students who were enrolled in statistics courses. Variables in the model included gender, mathematics ability, trait test anxiety (trait worry and trait emotionality as separate variables), statistics course anxiety, statistics achievement (scores on midterm examinations),…
Multiple statistical tests: Lessons from a d20
Madan, Christopher R.
2016-01-01
Statistical analyses are often conducted with α= .05. When multiple statistical tests are conducted, this procedure needs to be adjusted to compensate for the otherwise inflated Type I error. In some instances in tabletop gaming, sometimes it is desired to roll a 20-sided die (or 'd20') twice and take the greater outcome. Here I draw from probability theory and the case of a d20, where the probability of obtaining any specific outcome is 1/ 20, to determine the probability of obtaining a specific outcome (Type-I error) at least once across repeated, independent statistical tests. PMID:27347382
Multiple statistical tests: lessons from a d20.
Madan, Christopher R
2016-01-01
Statistical analyses are often conducted with α=.05. When multiple statistical tests are conducted, this procedure needs to be adjusted to compensate for the otherwise inflated Type I error. In some instances in tabletop gaming, sometimes it is desired to roll a 20-sided dice (or `d20') twice and take the greater outcome. Here I draw from probability theory and the case of a d20, where the probability of obtaining any specific outcome is 1/20, to determine the probability of obtaining a specific outcome (Type-I error) at least once across repeated, independent statistical tests. PMID:27347382
Statistical Evaluation of Molecular Contamination During Spacecraft Thermal Vacuum Test
NASA Technical Reports Server (NTRS)
Chen, Philip; Hedgeland, Randy; Montoya, Alex; Roman-Velazquez, Juan; Dunn, Jamie; Colony, Joe; Petitto, Joseph
1998-01-01
The purpose of this paper is to evaluate the statistical molecular contamination data with a goal to improve spacecraft contamination control. The statistical data was generated in typical thermal vacuum tests at the National Aeronautics and Space Administration, Goddard Space Flight Center (GSFC). The magnitude of material outgassing was measured using a Quartz Crystal Microbalance (QCM) device during the test. A solvent rinse sample was taken at the conclusion of each test. Then detailed qualitative and quantitative measurements were obtained through chemical analyses. All data used in this study encompassed numerous spacecraft tests in recent years.
Statistical Evaluation of Molecular Contamination During Spacecraft Thermal Vacuum Test
NASA Technical Reports Server (NTRS)
Chen, Philip; Hedgeland, Randy; Montoya, Alex; Roman-Velazquez, Juan; Dunn, Jamie; Colony, Joe; Petitto, Joseph
1999-01-01
The purpose of this paper is to evaluate the statistical molecular contamination data with a goal to improve spacecraft contamination control. The statistical data was generated in typical thermal vacuum tests at the National Aeronautics and Space Administration, Goddard Space Flight Center (GSFC). The magnitude of material outgassing was measured using a Quartz Crystal Microbalance (QCNO device during the test. A solvent rinse sample was taken at the conclusion of each test. Then detailed qualitative and quantitative measurements were obtained through chemical analyses. All data used in this study encompassed numerous spacecraft tests in recent years.
Statistical Evaluation of Molecular Contamination During Spacecraft Thermal Vacuum Test
NASA Technical Reports Server (NTRS)
Chen, Philip; Hedgeland, Randy; Montoya, Alex; Roman-Velazquez, Juan; Dunn, Jamie; Colony, Joe; Petitto, Joseph
1997-01-01
The purpose of this paper is to evaluate the statistical molecular contamination data with a goal to improve spacecraft contamination control. The statistical data was generated in typical thermal vacuum tests at the National Aeronautics and Space Administration, Goddard Space Flight Center (GSFC). The magnitude of material outgassing was measured using a Quartz Crystal Microbalance (QCM) device during the test. A solvent rinse sample was taken at the conclusion of the each test. Then detailed qualitative and quantitative measurements were obtained through chemical analyses. All data used in this study encompassed numerous spacecraft tests in recent years.
Rabinowitz, Daniel
2003-05-01
The focus of this work is the TDT-type and family-based test statistics used for adjusting for potential confounding due to population heterogeneity or misspecified allele frequencies. A variety of heuristics have been used to motivate and derive these statistics, and the statistics have been developed for a variety of analytic goals. There appears to be no general theoretical framework, however, that may be used to evaluate competing approaches. Furthermore, there is no framework to guide the development of efficient TDT-type and family-based methods for analytic goals for which methods have not yet been proposed. The purpose of this paper is to present a theoretical framework that serves both to identify the information which is available to methods that are immune to confounding due to population heterogeneity or misspecified allele frequencies, and to inform the construction of efficient unbiased tests in novel settings. The development relies on the existence of a characterization of the null hypothesis in terms of a completely specified conditional distribution of transmitted genotypes. An important observation is that, with such a characterization, when the conditioning event is unobserved or incomplete, there is statistical information that cannot be exploited by any exact conditional test. The main technical result of this work is an approach to computing test statistics for local alternatives that exploit all of the available statistical information.
Has Testing for Statistical Significance Outlived Its Usefulness?
ERIC Educational Resources Information Center
McLean, James E.; Ernest, James M.
The research methodology literature in recent years has included a full frontal assault on statistical significance testing. An entire edition of "Experimental Education" explored this controversy. The purpose of this paper is to promote the position that while significance testing by itself may be flawed, it has not outlived its usefulness.…
Model of risk assessment under ballistic statistical tests
NASA Astrophysics Data System (ADS)
Gabrovski, Ivan; Karakaneva, Juliana
The material presents the application of a mathematical method for risk assessment under statistical determination of the ballistic limits of the protection equipment. The authors have implemented a mathematical model based on Pierson's criteria. The software accomplishment of the model allows to evaluate the V50 indicator and to assess the statistical hypothesis' reliability. The results supply the specialists with information about the interval valuations of the probability determined during the testing process.
Pass-Fail Testing: Statistical Requirements and Interpretations
Gilliam, David; Leigh, Stefan; Rukhin, Andrew; Strawderman, William
2009-01-01
Performance standards for detector systems often include requirements for probability of detection and probability of false alarm at a specified level of statistical confidence. This paper reviews the accepted definitions of confidence level and of critical value. It describes the testing requirements for establishing either of these probabilities at a desired confidence level. These requirements are computable in terms of functions that are readily available in statistical software packages and general spreadsheet applications. The statistical interpretations of the critical values are discussed. A table is included for illustration, and a plot is presented showing the minimum required numbers of pass-fail tests. The results given here are applicable to one-sided testing of any system with performance characteristics conforming to a binomial distribution. PMID:27504221
Pass-Fail Testing: Statistical Requirements and Interpretations.
Gilliam, David; Leigh, Stefan; Rukhin, Andrew; Strawderman, William
2009-01-01
Performance standards for detector systems often include requirements for probability of detection and probability of false alarm at a specified level of statistical confidence. This paper reviews the accepted definitions of confidence level and of critical value. It describes the testing requirements for establishing either of these probabilities at a desired confidence level. These requirements are computable in terms of functions that are readily available in statistical software packages and general spreadsheet applications. The statistical interpretations of the critical values are discussed. A table is included for illustration, and a plot is presented showing the minimum required numbers of pass-fail tests. The results given here are applicable to one-sided testing of any system with performance characteristics conforming to a binomial distribution.
A Statistical Approach to Establishing Subsystem Environmental Test Specifications
NASA Technical Reports Server (NTRS)
Keegan, W. B.
1974-01-01
Results are presented of a research task to evaluate structural responses at various subsystem mounting locations during spacecraft level test exposures to the environments of mechanical shock, acoustic noise, and random vibration. This statistical evaluation is presented in the form of recommended subsystem test specifications for these three environments as normalized to a reference set of spacecraft test levels and are thus suitable for extrapolation to a set of different spacecraft test levels. The recommendations are dependent upon a subsystem's mounting location in a spacecraft, and information is presented on how to determine this mounting zone for a given subsystem.
Shukla, R.; Yu Daohai; Fulk, F.
1995-12-31
Short-term toxicity tests with aquatic organisms are a valuable measurement tool in the assessment of the toxicity of effluents, environmental samples and single chemicals. Currently toxicity tests are utilized in a wide range of US EPA regulatory activities including effluent discharge compliance. In the current approach for determining the No Observed Effect Concentration, an effluent concentration is presumed safe if there is no statistically significant difference in toxicant response versus control response. The conclusion of a safe concentration may be due to the fact that it truly is safe, or alternatively, that the ability of the statistical test to detect an effect, given its existence, is inadequate. Results of research of a new statistical approach, the basis of which is to move away from a demonstration of no difference to a demonstration of equivalence, will be discussed. The concept of observed confidence distributions, first suggested by Cox, is proposed as a measure of the strength of evidence for practically equivalent responses between a given effluent concentration and the control. The research included determination of intervals of practically equivalent responses as a function of the variability of control response. The approach is illustrated using reproductive data from tests with Ceriodaphnia dubia and survival and growth data from tests with fathead minnow. The data are from the US EPA`s National Reference Toxicant Database.
Innovative role of statistics in acid rain performance testing
Warren-Hicks, W.; Etchison, T.; Lieberman, E.R.
1995-12-31
Title IV of the Clean Air Act Amendments (CAAAs) of 1990 mandated that affected electric utilities reduce sulfur dioxide (SO{sub 2}) and nitrogen oxide (NO{sub x}) emissions, the primary precursors of acidic deposition, and included an innovative market-based SO{sub 2} regulatory program. A central element of the Acid Rain Program is the requirement that affected utility units install CEMS. This paper describes how the Acid Rain Regulations incorporated statistical procedures in the performance tests for continuous emissions monitoring systems (CEMS) and how statistical analysis was used to assess the appropriateness, stringency, and potential impact of various performance tests and standards that were considered for inclusion in the Acid Rain Regulations. Described here is the statistical analysis that was used to set a relative accuracy standard, establish the calculation procedures for filling in missing data when a monitor malfunctions, and evaluate the performance tests applied to petitions for alternative monitoring systems. The paper concludes that the statistical evaluations of proposed provisions of the Acid Rain Regulations resulted in the adoption of performance tests and standards that were scientifically substantiated, workable, and effective.
Statistical Studies on Sequential Probability Ratio Test for Radiation Detection
Warnick Kernan, Ding Yuan, et al.
2007-07-01
A Sequential Probability Ratio Test (SPRT) algorithm helps to increase the reliability and speed of radiation detection. This algorithm is further improved to reduce spatial gap and false alarm. SPRT, using Last-in-First-Elected-Last-Out (LIFELO) technique, reduces the error between the radiation measured and resultant alarm. Statistical analysis determines the reduction of spatial error and false alarm.
Wavelet analysis in ecology and epidemiology: impact of statistical tests.
Cazelles, Bernard; Cazelles, Kévin; Chavez, Mario
2014-02-01
Wavelet analysis is now frequently used to extract information from ecological and epidemiological time series. Statistical hypothesis tests are conducted on associated wavelet quantities to assess the likelihood that they are due to a random process. Such random processes represent null models and are generally based on synthetic data that share some statistical characteristics with the original time series. This allows the comparison of null statistics with those obtained from original time series. When creating synthetic datasets, different techniques of resampling result in different characteristics shared by the synthetic time series. Therefore, it becomes crucial to consider the impact of the resampling method on the results. We have addressed this point by comparing seven different statistical testing methods applied with different real and simulated data. Our results show that statistical assessment of periodic patterns is strongly affected by the choice of the resampling method, so two different resampling techniques could lead to two different conclusions about the same time series. Moreover, our results clearly show the inadequacy of resampling series generated by white noise and red noise that are nevertheless the methods currently used in the wide majority of wavelets applications. Our results highlight that the characteristics of a time series, namely its Fourier spectrum and autocorrelation, are important to consider when choosing the resampling technique. Results suggest that data-driven resampling methods should be used such as the hidden Markov model algorithm and the 'beta-surrogate' method.
Huang, Tzu-Hsueh; Ning, Xinghai; Wang, Xiaojian; Murthy, Niren; Tzeng, Yih-Ling; Dickson, Robert M
2015-02-01
Flow cytometry holds promise to accelerate antibiotic susceptibility determinations; however, without robust multidimensional statistical analysis, general discrimination criteria have remained elusive. In this study, a new statistical method, probability binning signature quadratic form (PB-sQF), was developed and applied to analyze flow cytometric data of bacterial responses to antibiotic exposure. Both sensitive lab strains (Escherichia coli and Pseudomonas aeruginosa) and a multidrug resistant, clinically isolated strain (E. coli) were incubated with the bacteria-targeted dye, maltohexaose-conjugated IR786, and each of many bactericidal or bacteriostatic antibiotics to identify changes induced around corresponding minimum inhibition concentrations (MIC). The antibiotic-induced damages were monitored by flow cytometry after 1-h incubation through forward scatter, side scatter, and fluorescence channels. The 3-dimensional differences between the flow cytometric data of the no-antibiotic treated bacteria and the antibiotic-treated bacteria were characterized by PB-sQF into a 1-dimensional linear distance. A 99% confidence level was established by statistical bootstrapping for each antibiotic-bacteria pair. For the susceptible E. coli strain, statistically significant increments from this 99% confidence level were observed from 1/16x MIC to 1x MIC for all the antibiotics. The same increments were recorded for P. aeruginosa, which has been reported to cause difficulty in flow-based viability tests. For the multidrug resistant E. coli, significant distances from control samples were observed only when an effective antibiotic treatment was utilized. Our results suggest that a rapid and robust antimicrobial susceptibility test (AST) can be constructed by statistically characterizing the differences between sample and control flow cytometric populations, even in a label-free scheme with scattered light alone. These distances vs paired controls coupled with rigorous
A critique of statistical hypothesis testing in clinical research
Raha, Somik
2011-01-01
Many have documented the difficulty of using the current paradigm of Randomized Controlled Trials (RCTs) to test and validate the effectiveness of alternative medical systems such as Ayurveda. This paper critiques the applicability of RCTs for all clinical knowledge-seeking endeavors, of which Ayurveda research is a part. This is done by examining statistical hypothesis testing, the underlying foundation of RCTs, from a practical and philosophical perspective. In the philosophical critique, the two main worldviews of probability are that of the Bayesian and the frequentist. The frequentist worldview is a special case of the Bayesian worldview requiring the unrealistic assumptions of knowing nothing about the universe and believing that all observations are unrelated to each other. Many have claimed that the first belief is necessary for science, and this claim is debunked by comparing variations in learning with different prior beliefs. Moving beyond the Bayesian and frequentist worldviews, the notion of hypothesis testing itself is challenged on the grounds that a hypothesis is an unclear distinction, and assigning a probability on an unclear distinction is an exercise that does not lead to clarity of action. This critique is of the theory itself and not any particular application of statistical hypothesis testing. A decision-making frame is proposed as a way of both addressing this critique and transcending ideological debates on probability. An example of a Bayesian decision-making approach is shown as an alternative to statistical hypothesis testing, utilizing data from a past clinical trial that studied the effect of Aspirin on heart attacks in a sample population of doctors. As a big reason for the prevalence of RCTs in academia is legislation requiring it, the ethics of legislating the use of statistical methods for clinical research is also examined. PMID:22022152
A critique of statistical hypothesis testing in clinical research.
Raha, Somik
2011-07-01
Many have documented the difficulty of using the current paradigm of Randomized Controlled Trials (RCTs) to test and validate the effectiveness of alternative medical systems such as Ayurveda. This paper critiques the applicability of RCTs for all clinical knowledge-seeking endeavors, of which Ayurveda research is a part. This is done by examining statistical hypothesis testing, the underlying foundation of RCTs, from a practical and philosophical perspective. In the philosophical critique, the two main worldviews of probability are that of the Bayesian and the frequentist. The frequentist worldview is a special case of the Bayesian worldview requiring the unrealistic assumptions of knowing nothing about the universe and believing that all observations are unrelated to each other. Many have claimed that the first belief is necessary for science, and this claim is debunked by comparing variations in learning with different prior beliefs. Moving beyond the Bayesian and frequentist worldviews, the notion of hypothesis testing itself is challenged on the grounds that a hypothesis is an unclear distinction, and assigning a probability on an unclear distinction is an exercise that does not lead to clarity of action. This critique is of the theory itself and not any particular application of statistical hypothesis testing. A decision-making frame is proposed as a way of both addressing this critique and transcending ideological debates on probability. An example of a Bayesian decision-making approach is shown as an alternative to statistical hypothesis testing, utilizing data from a past clinical trial that studied the effect of Aspirin on heart attacks in a sample population of doctors. As a big reason for the prevalence of RCTs in academia is legislation requiring it, the ethics of legislating the use of statistical methods for clinical research is also examined.
A statistical test to determine the quality of accelerometer data.
Slaven, J E; Andrew, M E; Violanti, J M; Burchfiel, C M; Vila, B J
2006-04-01
Accelerometer data quality can be inadequate due to data corruption or to non-compliance of the subject with regard to study protocols. We propose a simple statistical test to determine if accelerometer data are of good quality and can be used for analysis or if the data are of poor quality and should be discarded. We tested several data evaluation methods using a group of 105 subjects who wore Motionlogger actigraphs (Ambulatory Monitoring, Inc.) over a 15 day period to assess sleep quality in a study of health outcomes associated with stress among police officers. Using leave-one-out cross-validation and calibration-testing methods of discrimination statistics, error rates for the methods ranged from 0.0167 to 0.4046. We found that the best method was to use the overall average distance between consecutive time points and the overall average mean amplitude of consecutive time points. These values gave us a classification error rate of 0.0167. The average distance between points is a measure of smoothness in the data, and the average mean amplitude between points gave an average reading. Both of these values were then normed to determine a final statistic, K, which was then compared to a cut-off value, K(C), to determine data quality.
Statistical Treatment of Earth Observing System Pyroshock Separation Test Data
NASA Technical Reports Server (NTRS)
McNelis, Anne M.; Hughes, William O.
1998-01-01
The Earth Observing System (EOS) AM-1 spacecraft for NASA's Mission to Planet Earth is scheduled to be launched on an Atlas IIAS vehicle in June of 1998. One concern is that the instruments on the EOS spacecraft are sensitive to the shock-induced vibration produced when the spacecraft separates from the launch vehicle. By employing unique statistical analysis to the available ground test shock data, the NASA Lewis Research Center found that shock-induced vibrations would not be as great as the previously specified levels of Lockheed Martin. The EOS pyroshock separation testing, which was completed in 1997, produced a large quantity of accelerometer data to characterize the shock response levels at the launch vehicle/spacecraft interface. Thirteen pyroshock separation firings of the EOS and payload adapter configuration yielded 78 total measurements at the interface. The multiple firings were necessary to qualify the newly developed Lockheed Martin six-hardpoint separation system. Because of the unusually large amount of data acquired, Lewis developed a statistical methodology to predict the maximum expected shock levels at the interface between the EOS spacecraft and the launch vehicle. Then, this methodology, which is based on six shear plate accelerometer measurements per test firing at the spacecraft/launch vehicle interface, was used to determine the shock endurance specification for EOS. Each pyroshock separation test of the EOS spacecraft simulator produced its own set of interface accelerometer data. Probability distributions, histograms, the median, and higher order moments (skew and kurtosis) were analyzed. The data were found to be lognormally distributed, which is consistent with NASA pyroshock standards. Each set of lognormally transformed test data produced was analyzed to determine if the data should be combined statistically. Statistical testing of the data's standard deviations and means (F and t testing, respectively) determined if data sets were
Statistical process control testing of electronic security equipment
Murray, D.W.; Spencer, D.D.
1994-06-01
Statistical Process Control testing of manufacturing processes began back in the 1940`s with the development of Process Control Charts by Dr. Walter A. Shewart. Sandia National Laboratories has developed an application of the SPC method for performance testing of electronic security equipment. This paper documents the evaluation of this testing methodology applied to electronic security equipment and an associated laptop computer-based system for obtaining and analyzing the test data. Sandia developed this SPC sensor performance testing method primarily for use on portal metal detectors, but, has evaluated it for testing of an exterior intrusion detection sensor and other electronic security devices. This method is an alternative to the traditional binomial (alarm or no-alarm) performance testing. The limited amount of information in binomial data drives the number of tests necessary to meet regulatory requirements to unnecessarily high levels. For example, a requirement of a 0.85 probability of detection with a 90% confidence requires a minimum of 19 alarms out of 19 trials. By extracting and analyzing measurement (variables) data whenever possible instead of the more typical binomial data, the user becomes more informed about equipment health with fewer tests (as low as five per periodic evaluation).
n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator
2012-09-12
nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) is a comprehensive well test analysis software package. It provides a user-interface, a well test analysis model and many tools to analyze both field and simulated data. The well test analysis model simulates a single-phase, one-dimensional, radial/non-radial flow regime, with a borehole at the center of the modeled flow system. nSIGHTS solves the radially symmetric n-dimensional forward flow problem using a solver based on a graph-theoretic approach. The results of the forward simulation are pressure, and flow rate, given all the input parameters. The parameter estimation portion of nSIGHTS uses a perturbation-based approach to interpret the best-fit well and reservoir parameters, given an observed dataset of pressure and flow rate.
n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator
2012-09-12
nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) is a comprehensive well test analysis software package. It provides a user-interface, a well test analysis model and many tools to analyze both field and simulated data. The well test analysis model simulates a single-phase, one-dimensional, radial/non-radial flow regime, with a borehole at the center of the modeled flow system. nSIGHTS solves the radially symmetric n-dimensional forward flow problem using a solver based on a graph-theoretic approach.more » The results of the forward simulation are pressure, and flow rate, given all the input parameters. The parameter estimation portion of nSIGHTS uses a perturbation-based approach to interpret the best-fit well and reservoir parameters, given an observed dataset of pressure and flow rate.« less
Statistical analysis of test data for APM rod issue
Edwards, T.B.; Harris, S.P.; Reeve, C.P.
1992-05-01
The uncertainty associated with the use of the K-Reactor axial power monitors (APMs) to measure roof-top-ratios is investigated in this report. Internal heating test data acquired under both DC-flow conditions and AC-flow conditions have been analyzed. These tests were conducted to simulate gamma heating at the lower power levels planned for reactor operation. The objective of this statistical analysis is to investigate the relationship between the observed and true roof-top-ratio (RTR) values and associated uncertainties at power levels within this lower operational range. Conditional on a given, known power level, a prediction interval for the true RTR value corresponding to a new, observed RTR is given. This is done for a range of power levels. Estimates of total system uncertainty are also determined by combining the analog-to-digital converter uncertainty with the results from the test data.
Quantum Statistical Testing of a Quantum Random Number Generator
Humble, Travis S
2014-01-01
The unobservable elements in a quantum technology, e.g., the quantum state, complicate system verification against promised behavior. Using model-based system engineering, we present methods for verifying the opera- tion of a prototypical quantum random number generator. We begin with the algorithmic design of the QRNG followed by the synthesis of its physical design requirements. We next discuss how quantum statistical testing can be used to verify device behavior as well as detect device bias. We conclude by highlighting how system design and verification methods must influence effort to certify future quantum technologies.
Why the null matters: statistical tests, random walks and evolution.
Sheets, H D; Mitchell, C E
2001-01-01
A number of statistical tests have been developed to determine what type of dynamics underlie observed changes in morphology in evolutionary time series, based on the pattern of change within the time series. The theory of the 'scaled maximum', the 'log-rate-interval' (LRI) method, and the Hurst exponent all operate on the same principle of comparing the maximum change, or rate of change, in the observed dataset to the maximum change expected of a random walk. Less change in a dataset than expected of a random walk has been interpreted as indicating stabilizing selection, while more change implies directional selection. The 'runs test' in contrast, operates on the sequencing of steps, rather than on excursion. Applications of these tests to computer generated, simulated time series of known dynamical form and various levels of additive noise indicate that there is a fundamental asymmetry in the rate of type II errors of the tests based on excursion: they are all highly sensitive to noise in models of directional selection that result in a linear trend within a time series, but are largely noise immune in the case of a simple model of stabilizing selection. Additionally, the LRI method has a lower sensitivity than originally claimed, due to the large range of LRI rates produced by random walks. Examination of the published results of these tests show that they have seldom produced a conclusion that an observed evolutionary time series was due to directional selection, a result which needs closer examination in light of the asymmetric response of these tests.
Jones, P L; Swain, W T; Trammell, C J
1999-01-01
When a population is too large for exhaustive study, as is the case for all possible uses of a software system, a statistically correct sample must be drawn as a basis for inferences about the population. A Markov chain usage model is an engineering formalism that represents the population of possible uses for which a product is to be tested. In statistical testing of software based on a Markov chain usage model, the rich body of analytical results available for Markov chains provides numerous insights that can be used in both product development and test planing. A usage model is based on specifications rather than code, so insights that result from model building can inform product decisions in the early stages of a project when the opportunity to prevent problems is the greatest. Statistical testing based on a usage model provides a sound scientific basis for quantifying the reliability of software. PMID:10459417
Testing the validity of Bose-Einstein statistics in molecules
NASA Astrophysics Data System (ADS)
Cancio Pastor, P.; Galli, I.; Giusfredi, G.; Mazzotti, D.; De Natale, P.
2015-12-01
The search for small violations of the validity of the symmetrization postulate and of the spin-statistics connection (SSC) has been addressed in the last four decades by experimental tests performed in different physical systems of identical fermions or bosons. In parallel and consequently, theories extending the quantum mechanics to a more general level have been proposed to explain such possible violations. In this paper, we present the most stringent test to a possible violation of the SSC under permutation of the bosonic 16O nuclei in the 12CO162 molecule. An upper limit of 3.8 ×10-12 for an SSC-anomalous CO2 molecule is obtained using saturated-absorption cavity ring-down spectroscopy in the SSC-forbidden (0001 -0000 ) R (25) rovibrational transition of 12CO162 at a 4.25 -μ m wavelength. Quantum mechanics implications of this result are discussed in the frame of the q -mutator theory. Finally, the perspective of stringent experimental tests of the symmetrization postulate in molecules that contain three or more identical nuclei is discussed.
A statistical design for testing apomictic diversification through linkage analysis.
Zeng, Yanru; Hou, Wei; Song, Shuang; Feng, Sisi; Shen, Lin; Xia, Guohua; Wu, Rongling
2014-03-01
The capacity of apomixis to generate maternal clones through seed reproduction has made it a useful characteristic for the fixation of heterosis in plant breeding. It has been observed that apomixis displays pronounced intra- and interspecific diversification, but the genetic mechanisms underlying this diversification remains elusive, obstructing the exploitation of this phenomenon in practical breeding programs. By capitalizing on molecular information in mapping populations, we describe and assess a statistical design that deploys linkage analysis to estimate and test the pattern and extent of apomictic differences at various levels from genotypes to species. The design is based on two reciprocal crosses between two individuals each chosen from a hermaphrodite or monoecious species. A multinomial distribution likelihood is constructed by combining marker information from two crosses. The EM algorithm is implemented to estimate the rate of apomixis and test its difference between two plant populations or species as the parents. The design is validated by computer simulation. A real data analysis of two reciprocal crosses between hickory (Carya cathayensis) and pecan (C. illinoensis) demonstrates the utilization and usefulness of the design in practice. The design provides a tool to address fundamental and applied questions related to the evolution and breeding of apomixis.
A Unifying Framework for Teaching Nonparametric Statistical Tests
ERIC Educational Resources Information Center
Bargagliotti, Anna E.; Orrison, Michael E.
2014-01-01
Increased importance is being placed on statistics at both the K-12 and undergraduate level. Research divulging effective methods to teach specific statistical concepts is still widely sought after. In this paper, we focus on best practices for teaching topics in nonparametric statistics at the undergraduate level. To motivate the work, we…
Development and testing of improved statistical wind power forecasting methods.
Mendes, J.; Bessa, R.J.; Keko, H.; Sumaili, J.; Miranda, V.; Ferreira, C.; Gama, J.; Botterud, A.; Zhou, Z.; Wang, J.
2011-12-06
Wind power forecasting (WPF) provides important inputs to power system operators and electricity market participants. It is therefore not surprising that WPF has attracted increasing interest within the electric power industry. In this report, we document our research on improving statistical WPF algorithms for point, uncertainty, and ramp forecasting. Below, we provide a brief introduction to the research presented in the following chapters. For a detailed overview of the state-of-the-art in wind power forecasting, we refer to [1]. Our related work on the application of WPF in operational decisions is documented in [2]. Point forecasts of wind power are highly dependent on the training criteria used in the statistical algorithms that are used to convert weather forecasts and observational data to a power forecast. In Chapter 2, we explore the application of information theoretic learning (ITL) as opposed to the classical minimum square error (MSE) criterion for point forecasting. In contrast to the MSE criterion, ITL criteria do not assume a Gaussian distribution of the forecasting errors. We investigate to what extent ITL criteria yield better results. In addition, we analyze time-adaptive training algorithms and how they enable WPF algorithms to cope with non-stationary data and, thus, to adapt to new situations without requiring additional offline training of the model. We test the new point forecasting algorithms on two wind farms located in the U.S. Midwest. Although there have been advancements in deterministic WPF, a single-valued forecast cannot provide information on the dispersion of observations around the predicted value. We argue that it is essential to generate, together with (or as an alternative to) point forecasts, a representation of the wind power uncertainty. Wind power uncertainty representation can take the form of probabilistic forecasts (e.g., probability density function, quantiles), risk indices (e.g., prediction risk index) or scenarios
Strong gravitational lensing statistics as a test of cosmogonic scenarios
NASA Technical Reports Server (NTRS)
Cen, Renyue; Gott, J. Richard, III; Ostriker, Jeremiah P.; Turner, Edwin L.
1994-01-01
Gravitational lensing statistics can provide a direct and powerful test of cosmic structure formation theories. Since lensing tests, directly, the magnitude of the nonlinear mass density fluctuations on lines of sight to distant objects, no issues of 'bias' (of mass fluctuations with respect to galaxy density fluctuations) exist here, although lensing observations provide their own ambiguities of interpretation. We develop numerical techniques for generating model density distributions with the very large spatial dynamic range required by lensing considerations and for identifying regions of the simulations capable of multiple image lensing in a conservative and computationally efficient way that should be accurate for splittings significantly larger than 3 seconds. Applying these techniques to existing standard Cold dark matter (CDM) (Omega = 1) and Primeval Baryon Isocurvature (PBI) (Omega = 0.2) simulations (normalized to the Cosmic Background Explorer Satellite (COBE) amplitude), we find that the CDM model predicts large splitting (greater than 8 seconds) lensing events roughly an order-of-magnitude more frequently than the PBI model. Under the reasonable but idealized assumption that lensing structrues can be modeled as singular isothermal spheres (SIS), the predictions can be directly compared to observations of lensing events in quasar samples. Several large splitting (Delta Theta is greater than 8 seconds) cases are predicted in the standard CDM model (the exact number being dependent on the treatment of amplification bias), whereas none is observed. In a formal sense, the comparison excludes the CDM model at high confidence (essentially for the same reason that CDM predicts excessive small-scale cosmic velocity dispersions.) A very rough assessment of low-density but flat CDM model (Omega = 0.3, Lambda/3H(sup 2 sub 0) = 0.7) indicates a far lower and probably acceptable level of lensing. The PBI model is consistent with, but not strongly tested by, the
Testing the Limits of Statistical Learning for Word Segmentation
Johnson, Elizabeth K.; Tyler, Michael D.
2009-01-01
Past research has demonstrated that infants can rapidly extract syllable distribution information from an artificial language and use this knowledge to infer likely word boundaries in speech. However, artificial languages are extremely simplified with respect to natural language. In this study, we ask whether infants’ ability to track transitional probabilities between syllables in an artificial language can scale up to the challenge of natural language. We do so by testing both 5.5- and 8-month-olds’ ability to segment an artificial language containing four words of uniform length (all CVCV) or four words of varying length (two CVCV, two CVCVCV). The transitional probability cues to word boundaries were held equal across the two languages. Both age groups segmented the language containing words of uniform length, demonstrating that even 5.5-month-olds are extremely sensitive to the conditional probabilities in their environment. However, neither age group succeeded in segmenting the language containing words of varying length, despite the fact that the transitional probability cues defining word boundaries were equally strong in the two languages. We conclude that infants’ statistical learning abilities may not be as robust as earlier studies have suggested. PMID:20136930
Decision Support Systems: Applications in Statistics and Hypothesis Testing.
ERIC Educational Resources Information Center
Olsen, Christopher R.; Bozeman, William C.
1988-01-01
Discussion of the selection of appropriate statistical procedures by educators highlights a study conducted to investigate the effectiveness of decision aids in facilitating the use of appropriate statistics. Experimental groups and a control group using a printed flow chart, a computer-based decision aid, and a standard text are described. (11…
Statistical Measures, Hypotheses, and Tests in Applied Research
ERIC Educational Resources Information Center
Saville, David J.; Rowarth, Jacqueline S.
2008-01-01
This article reviews and discusses the use of statistical concepts in a natural resources and life sciences journal on the basis of a census of the articles published in a recent issue of the "Agronomy Journal" and presents a flow chart and a graph that display the inter-relationships between the most commonly used statistical terms. It also…
Links to sources of cancer-related statistics, including the Surveillance, Epidemiology and End Results (SEER) Program, SEER-Medicare datasets, cancer survivor prevalence data, and the Cancer Trends Progress Report.
A weighted generalized score statistic for comparison of predictive values of diagnostic tests.
Kosinski, Andrzej S
2013-03-15
Positive and negative predictive values are important measures of a medical diagnostic test performance. We consider testing equality of two positive or two negative predictive values within a paired design in which all patients receive two diagnostic tests. The existing statistical tests for testing equality of predictive values are either Wald tests based on the multinomial distribution or the empirical Wald and generalized score tests within the generalized estimating equations (GEE) framework. As presented in the literature, these test statistics have considerably complex formulas without clear intuitive insight. We propose their re-formulations that are mathematically equivalent but algebraically simple and intuitive. As is clearly seen with a new re-formulation we presented, the generalized score statistic does not always reduce to the commonly used score statistic in the independent samples case. To alleviate this, we introduce a weighted generalized score (WGS) test statistic that incorporates empirical covariance matrix with newly proposed weights. This statistic is simple to compute, always reduces to the score statistic in the independent samples situation, and preserves type I error better than the other statistics as demonstrated by simulations. Thus, we believe that the proposed WGS statistic is the preferred statistic for testing equality of two predictive values and for corresponding sample size computations. The new formulas of the Wald statistics may be useful for easy computation of confidence intervals for difference of predictive values. The introduced concepts have potential to lead to development of the WGS test statistic in a general GEE setting.
Ensuring Positiveness of the Scaled Difference Chi-Square Test Statistic
ERIC Educational Resources Information Center
Satorra, Albert; Bentler, Peter M.
2010-01-01
A scaled difference test statistic T[tilde][subscript d] that can be computed from standard software of structural equation models (SEM) by hand calculations was proposed in Satorra and Bentler (Psychometrika 66:507-514, 2001). The statistic T[tilde][subscript d] is asymptotically equivalent to the scaled difference test statistic T[bar][subscript…
Understanding the Sampling Distribution and Its Use in Testing Statistical Significance.
ERIC Educational Resources Information Center
Breunig, Nancy A.
Despite the increasing criticism of statistical significance testing by researchers, particularly in the publication of the 1994 American Psychological Association's style manual, statistical significance test results are still popular in journal articles. For this reason, it remains important to understand the logic of inferential statistics. A…
The Geometry of Probability, Statistics, and Test Theory.
ERIC Educational Resources Information Center
Zimmerman, Donald W.; Zumbo, Bruno D.
2001-01-01
Presents a model of tests and measurement that identifies test scores with Hilbert space vectors and true and error components of scores with linear operators. This geometric point of view brings to light relations among elementary concepts in test theory, including reliability, validity, and parallel tests. (Author/SLD)
Stork, LeAnna M.; Gennings, Chris; Carchman, Richard; Carter, Jr., Walter H.; Pounds, Joel G.; Mumtaz, Moiz
2006-12-01
Several assumptions, defined and undefined, are used in the toxicity assessment of chemical mixtures. In scientific practice mixture components in the low-dose region, particularly subthreshold doses, are often assumed to behave additively (i.e., zero interaction) based on heuristic arguments. This assumption has important implications in the practice of risk assessment, but has not been experimentally tested. We have developed methodology to test for additivity in the sense of Berenbaum (Advances in Cancer Research, 1981), based on the statistical equivalence testing literature where the null hypothesis of interaction is rejected for the alternative hypothesis of additivity when data support the claim. The implication of this approach is that conclusions of additivity are made with a false positive rate controlled by the experimenter. The claim of additivity is based on prespecified additivity margins, which are chosen using expert biological judgment such that small deviations from additivity, which are not considered to be biologically important, are not statistically significant. This approach is in contrast to the usual hypothesis-testing framework that assumes additivity in the null hypothesis and rejects when there is significant evidence of interaction. In this scenario, failure to reject may be due to lack of statistical power making the claim of additivity problematic. The proposed method is illustrated in a mixture of five organophosphorus pesticides that were experimentally evaluated alone and at relevant mixing ratios. Motor activity was assessed in adult male rats following acute exposure. Four low-dose mixture groups were evaluated. Evidence of additivity is found in three of the four low-dose mixture groups.The proposed method tests for additivity of the whole mixture and does not take into account subset interactions (e.g., synergistic, antagonistic) that may have occurred and cancelled each other out.
New heterogeneous test statistics for the unbalanced fixed-effect nested design.
Guo, Jiin-Huarng; Billard, L; Luh, Wei-Ming
2011-05-01
When the underlying variances are unknown or/and unequal, using the conventional F test is problematic in the two-factor hierarchical data structure. Prompted by the approximate test statistics (Welch and Alexander-Govern methods), the authors develop four new heterogeneous test statistics to test factor A and factor B nested within A for the unbalanced fixed-effect two-stage nested design under variance heterogeneity. The actual significance levels and statistical power of the test statistics were compared in a simulation study. The results show that the proposed procedures maintain better Type I error rate control and have greater statistical power than those obtained by the conventional F test in various conditions. Therefore, the proposed test statistics are recommended in terms of robustness and easy implementation.
Statistical tests for closure of plate motion circuits
NASA Technical Reports Server (NTRS)
Gordon, Richard G.; Stein, Seth; Demets, Charles; Argus, Donald F.
1987-01-01
Two methods, one based on a chi-square test and the second on an F-ratio test, of testing for the plate motion circuit closures are described and evaluated. The chi-square test is used to evaluate goodness of fit, and it is assumed that the assigned errors are accurate estimates of the true errors in the data. The F-ratio test is used to compare variances of distributions, and it is assumed that the relative values of assigned error are accurate. The two methods are applied to the data of Minster and Jordan (1978) on the motion of the three plates that meet at the Galapagos Triple Junction, and the motion of the three plates that meet at the Indian Ocean Triple Junction. It is noted that the F-ratio plate circuit closure test is more useful than the chi-square test for identifying systematic misfits in data because the chi-square test overestimates the errors of plate motion data.
Estimating Statistical Power When Making Adjustments for Multiple Tests
ERIC Educational Resources Information Center
Porter, Kristin E.
2016-01-01
In recent years, there has been increasing focus on the issue of multiple hypotheses testing in education evaluation studies. In these studies, researchers are typically interested in testing the effectiveness of an intervention on multiple outcomes, for multiple subgroups, at multiple points in time or across multiple treatment groups. When…
Statistical Revisions in the Washington Pre-College Testing Program.
ERIC Educational Resources Information Center
Beanblossom, Gary F.; And Others
The Washington Pre-College (WPC) program decided, in fall 1967, to inaugurate in April 1968 the testing of high school students during the spring of their junior year. The advantages of this shift from senior year testing were to provide guidance data for earlier, more extensive use in high school and to make these data available to colleges at…
ERIC Educational Resources Information Center
Monterde-i-Bort, Hector; Frias-Navarro, Dolores; Pascual-Llobell, Juan
2010-01-01
The empirical study we present here deals with a pedagogical issue that has not been thoroughly explored up until now in our field. Previous empirical studies in other sectors have identified the opinions of researchers about this topic, showing that completely unacceptable interpretations have been made of significance tests and other statistical…
Mathur, Sunil; Sadana, Ajit
2015-12-01
We present a rank-based test statistic for the identification of differentially expressed genes using a distance measure. The proposed test statistic is highly robust against extreme values and does not assume the distribution of parent population. Simulation studies show that the proposed test is more powerful than some of the commonly used methods, such as paired t-test, Wilcoxon signed rank test, and significance analysis of microarray (SAM) under certain non-normal distributions. The asymptotic distribution of the test statistic, and the p-value function are discussed. The application of proposed method is shown using a real-life data set.
Evaluation of a New Mean Scaled and Moment Adjusted Test Statistic for SEM
ERIC Educational Resources Information Center
Tong, Xiaoxiao; Bentler, Peter M.
2013-01-01
Recently a new mean scaled and skewness adjusted test statistic was developed for evaluating structural equation models in small samples and with potentially nonnormal data, but this statistic has received only limited evaluation. The performance of this statistic is compared to normal theory maximum likelihood and 2 well-known robust test…
NASA Technical Reports Server (NTRS)
Purves, L.; Strang, R. F.; Dube, M. P.; Alea, P.; Ferragut, N.; Hershfeld, D.
1983-01-01
The software and procedures of a system of programs used to generate a report of the statistical correlation between NASTRAN modal analysis results and physical tests results from modal surveys are described. Topics discussed include: a mathematical description of statistical correlation, a user's guide for generating a statistical correlation report, a programmer's guide describing the organization and functions of individual programs leading to a statistical correlation report, and a set of examples including complete listings of programs, and input and output data.
The Michigan Alcoholism Screening Test (MAST): A Statistical Validation Analysis
ERIC Educational Resources Information Center
Laux, John M.; Newman, Isadore; Brown, Russ
2004-01-01
This study extends the Michigan Alcoholism Screening Test (MAST; M. L. Selzer, 1971) literature base by examining 4 issues related to the validity of the MAST scores. Specifically, the authors examine the validity of the MAST scores in light of the presence of impression management, participant demographic variables, and item endorsement…
Spatial factors affecting statistical power in testing marine fauna displacement.
Pérez Lapeña, B; Wijnberg, K M; Stein, A; Hulscher, S J M H
2011-10-01
Impacts of offshore wind farms on marine fauna are largely unknown. Therefore, one commonly adheres to the precautionary principle, which states that one shall take action to avoid potentially damaging impacts on marine ecosystems, even when full scientific certainty is lacking. We implement this principle by means of a statistical power analysis including spatial factors. Implementation is based on geostatistical simulations, accommodating for zero-inflation in species data. We investigate scenarios in which an impact assessment still has to be carried out. Our results show that the environmental conditions at the time of the survey is the most influential factor on power. This is followed by survey effort and species abundance in the reference situation. Spatial dependence in species numbers at local scales affects power, but its effect is smaller for the scenarios investigated. Our findings can be used to improve effectiveness of the economical investment for monitoring surveys. In addition, unnecessary extra survey effort, and related costs, can be avoided when spatial dependence in species abundance is present and no improvement on power is achieved.
A Statistical Test of Uniformity in Solar Cycle Indices
NASA Technical Reports Server (NTRS)
Hathaway David H.
2012-01-01
Several indices are used to characterize the solar activity cycle. Key among these are: the International Sunspot Number, the Group Sunspot Number, Sunspot Area, and 10.7 cm Radio Flux. A valuable aspect of these indices is the length of the record -- many decades and many (different) 11-year cycles. However, this valuable length-of-record attribute has an inherent problem in that it requires many different observers and observing systems. This can lead to non-uniformity in the datasets and subsequent erroneous conclusions about solar cycle behavior. The sunspot numbers are obtained by counting sunspot groups and individual sunspots on a daily basis. This suggests that the day-to-day and month-to-month variations in these numbers should follow Poisson Statistics and be proportional to the square-root of the sunspot numbers themselves. Examining the historical records of these indices indicates that this is indeed the case - even with Sunspot Area and 10.7 cm Radio Flux. The ratios of the RMS variations to the square-root of the indices themselves are relatively constant with little variation over the phase of each solar cycle or from small to large solar cycles. There are, however, important step-like changes in these ratios associated with changes in observer and/or observer system. Here we show how these variations can be used to construct more uniform datasets.
Testing of hypotheses about altitude decompression sickness by statistical analyses
NASA Technical Reports Server (NTRS)
Van Liew, H. D.; Burkard, M. E.; Conkin, J.; Powell, M. R. (Principal Investigator)
1996-01-01
This communication extends a statistical analysis of forced-descent decompression sickness at altitude in exercising subjects (J Appl Physiol 1994; 76:2726-2734) with a data subset having an additional explanatory variable, rate of ascent. The original explanatory variables for risk-function analysis were environmental pressure of the altitude, duration of exposure, and duration of pure-O2 breathing before exposure; the best fit was consistent with the idea that instantaneous risk increases linearly as altitude exposure continues. Use of the new explanatory variable improved the fit of the smaller data subset, as indicated by log likelihood. Also, with ascent rate accounted for, replacement of the term for linear accrual of instantaneous risk by a term for rise and then decay made a highly significant improvement upon the original model (log likelihood increased by 37 log units). The authors conclude that a more representative data set and removal of the variability attributable to ascent rate allowed the rise-and-decay mechanism, which is expected from theory and observations, to become manifest.
Development and performances of a high statistics PMT test facility
NASA Astrophysics Data System (ADS)
Maximiliano Mollo, Carlos
2016-04-01
Since almost a century photomultipliers have been the main sensors for photon detection in nuclear and astro-particle physics experiments. In recent years the search for cosmic neutrinos gave birth to enormous size experiments (Antares, Kamiokande, Super-Kamiokande, etc.) and even kilometric scale experiments as ICECUBE and the future KM3NeT. A very large volume neutrino telescope like KM3NeT requires several hundreds of thousands photomultipliers. The performance of the telescope strictly depends on the performance of each PMT. For this reason, it is mandatory to measure the characteristics of each single sensor. The characterization of a PMT normally requires more than 8 hours mostly due to the darkening step. This means that it is not feasible to measure the parameters of each PMT of a neutrino telescope without a system able to test more than one PMT simultaneously. For this application, we have designed, developed and realized a system able to measure the main characteristics of 62 3-inch photomultipliers simultaneously. Two measurement sessions per day are possible. In this work, we describe the design constraints and how they have been satisfied. Finally, we show the performance of the system and the first results coming from the test of few thousand tested PMTs.
1993-02-01
In 1984, 99% of abortions conducted in Bombay, India, were of female fetuses. In 1986-87, 30,000-50,000 female fetuses were aborted in India. In 1987-88, 7 Delhi clinics conducted 13,000 sex determination tests. Thus, discrimination against females begins before birth in India. Some states (Maharashtra, Goa, and Gujarat) have drafted legislation to prevent the use of prenatal diagnostic tests (e.g., ultrasonography) for sex determination purposes. Families make decisions about an infant's nutrition based on the infant's sex so it is not surprising to see a higher incidence of morbidity among girls than boys (e.g., for respiratory infections in 1985, 55.5% vs. 27.3%). Consequently, they are more likely to die than boys. Even though vasectomy is simpler and safer than tubectomy, the government promotes female sterilizations. The percentage of all sexual sterilizations being tubectomy has increased steadily from 84% to 94% (1986-90). Family planning programs focus on female contraceptive methods, despite the higher incidence of adverse health effects from female methods (e.g., IUD causes pain and heavy bleeding). Some women advocates believe the effects to be so great that India should ban contraceptives and injectable contraceptives. The maternal mortality rate is quite high (460/100,000 live births), equaling a lifetime risk of 1:18 of a pregnancy-related death. 70% of these maternal deaths are preventable. Leading causes of maternal deaths in India are anemia, hemorrhage, eclampsia, sepsis, and abortion. Most pregnant women do not receive prenatal care. Untrained personnel attend about 70% of deliveries in rural areas and 29% in urban areas. Appropriate health services and other interventions would prevent the higher age specific death rates for females between 0 and 35 years old. Even though the government does provide maternal and child health services, it needs to stop decreasing resource allocate for health and start increasing it. PMID:12286355
ERIC Educational Resources Information Center
Denbleyker, John Nickolas
2012-01-01
The shortcomings of the proportion above cut (PAC) statistic used so prominently in the educational landscape renders it a very problematic measure for making correct inferences with student test data. The limitations of PAC-based statistics are more pronounced with cross-test comparisons due to their dependency on cut-score locations. A better…
ERIC Educational Resources Information Center
Norris, John M.
2015-01-01
Traditions of statistical significance testing in second language (L2) quantitative research are strongly entrenched in how researchers design studies, select analyses, and interpret results. However, statistical significance tests using "p" values are commonly misinterpreted by researchers, reviewers, readers, and others, leading to…
A Review of Post-1994 Literature on Whether Statistical Significance Tests Should Be Banned.
ERIC Educational Resources Information Center
Sullivan, Jeremy R.
This paper summarizes the literature regarding statistical significance testing with an emphasis on: (1) the post-1994 literature in various disciplines; (2) alternatives to statistical significance testing; and (3) literature exploring why researchers have demonstrably failed to be influenced by the 1994 American Psychological Association…
"What If" Analyses: Ways to Interpret Statistical Significance Test Results Using EXCEL or "R"
ERIC Educational Resources Information Center
Ozturk, Elif
2012-01-01
The present paper aims to review two motivations to conduct "what if" analyses using Excel and "R" to understand the statistical significance tests through the sample size context. "What if" analyses can be used to teach students what statistical significance tests really do and in applied research either prospectively to estimate what sample size…
EVALUATION OF A NEW MEAN SCALED AND MOMENT ADJUSTED TEST STATISTIC FOR SEM.
Tong, Xiaoxiao; Bentler, Peter M
2013-01-01
Recently a new mean scaled and skewness adjusted test statistic was developed for evaluating structural equation models in small samples and with potentially nonnormal data, but this statistic has received only limited evaluation. The performance of this statistic is compared to normal theory maximum likelihood and two well-known robust test statistics. A modification to the Satorra-Bentler scaled statistic is developed for the condition that sample size is smaller than degrees of freedom. The behavior of the four test statistics is evaluated with a Monte Carlo confirmatory factor analysis study that varies seven sample sizes and three distributional conditions obtained using Headrick's fifth-order transformation to nonnormality. The new statistic performs badly in most conditions except under the normal distribution. The goodness-of-fit χ(2) test based on maximum-likelihood estimation performed well under normal distributions as well as under a condition of asymptotic robustness. The Satorra-Bentler scaled test statistic performed best overall, while the mean scaled and variance adjusted test statistic outperformed the others at small and moderate sample sizes under certain distributional conditions.
Nonparametric statistical tests for the continuous data: the basic concept and the practical use
2016-01-01
Conventional statistical tests are usually called parametric tests. Parametric tests are used more frequently than nonparametric tests in many medical articles, because most of the medical researchers are familiar with and the statistical software packages strongly support parametric tests. Parametric tests require important assumption; assumption of normality which means that distribution of sample means is normally distributed. However, parametric test can be misleading when this assumption is not satisfied. In this circumstance, nonparametric tests are the alternative methods available, because they do not required the normality assumption. Nonparametric tests are the statistical methods based on signs and ranks. In this article, we will discuss about the basic concepts and practical use of nonparametric tests for the guide to the proper use. PMID:26885295
Statistic Tests Aided Multi-Source dem Fusion
NASA Astrophysics Data System (ADS)
Fu, C. Y.; Tsay, J. R.
2016-06-01
Since the land surface has been changing naturally or manually, DEMs have to be updated continually to satisfy applications using the latest DEM at present. However, the cost of wide-area DEM production is too high. DEMs, which cover the same area but have different quality, grid sizes, generation time or production methods, are called as multi-source DEMs. It provides a solution to fuse multi-source DEMs for low cost DEM updating. The coverage of DEM has to be classified according to slope and visibility in advance, because the precisions of DEM grid points in different areas with different slopes and visibilities are not the same. Next, difference DEM (dDEM) is computed by subtracting two DEMs. It is assumed that dDEM, which only contains random error, obeys normal distribution. Therefore, student test is implemented for blunder detection and three kinds of rejected grid points are generated. First kind of rejected grid points is blunder points and has to be eliminated. Another one is the ones in change areas, where the latest data are regarded as their fusion result. Moreover, the DEM grid points of type I error are correct data and have to be reserved for fusion. The experiment result shows that using DEMs with terrain classification can obtain better blunder detection result. A proper setting of significant levels (α) can detect real blunders without creating too many type I errors. Weighting averaging is chosen as DEM fusion algorithm. The priori precisions estimated by our national DEM production guideline are applied to define weights. Fisher's test is implemented to prove that the priori precisions correspond to the RMSEs of blunder detection result.
Three-stage sequential statistical dissolution testing rules.
Tsong, Yi; Shen, Meiyu; Shah, Vinod P
2004-08-01
The U.S. Pharmacopoeia (USP) general monograph provides a standard for dissolution compliance with the requirements as stated in the individual USP monograph for a tablet or capsule dosage form. The USP monograph sets performance limit on dissolution in terms of a specific percentage Q that the drug product is required to be dissolved at a specified time. Japan Pharmacopoeia provides acceptance rules different from USP. However the objective of the acceptance rules was not defined in terms of the inference of the whole lot by either USP, European Pharmacopoeia (EP) or Japan Pharmacopoeia (JP). The operating characteristics' curves of these rules are all shown to be sensitive to the true mean dissolution and do not reject a lot which has a large percentage of tablets that dissolve with less than the specified limit Q. This is especially true when the mean dissolution is close to the specification value. We proposed that the goal of the dissolution test sampling plan is to accept a lot at least 90% of the tablets dissolved more than a pre-specified amount Q at the specific time. The group sequential procedure derived accordingly is shown to outperform both USP and JP in controlling the type I error rate under normality assumption.
Zhang, Fanghong; Miyaoka, Etsuo; Huang, Fuping; Tanaka, Yutaka
2015-01-01
The problem for establishing noninferiority is discussed between a new treatment and a standard (control) treatment with ordinal categorical data. A measure of treatment effect is used and a method of specifying noninferiority margin for the measure is provided. Two Z-type test statistics are proposed where the estimation of variance is constructed under the shifted null hypothesis using U-statistics. Furthermore, the confidence interval and the sample size formula are given based on the proposed test statistics. The proposed procedure is applied to a dataset from a clinical trial. A simulation study is conducted to compare the performance of the proposed test statistics with that of the existing ones, and the results show that the proposed test statistics are better in terms of the deviation from nominal level and the power.
NASA Technical Reports Server (NTRS)
Xu, Kuan-Man
2006-01-01
A new method is proposed to compare statistical differences between summary histograms, which are the histograms summed over a large ensemble of individual histograms. It consists of choosing a distance statistic for measuring the difference between summary histograms and using a bootstrap procedure to calculate the statistical significance level. Bootstrapping is an approach to statistical inference that makes few assumptions about the underlying probability distribution that describes the data. Three distance statistics are compared in this study. They are the Euclidean distance, the Jeffries-Matusita distance and the Kuiper distance. The data used in testing the bootstrap method are satellite measurements of cloud systems called cloud objects. Each cloud object is defined as a contiguous region/patch composed of individual footprints or fields of view. A histogram of measured values over footprints is generated for each parameter of each cloud object and then summary histograms are accumulated over all individual histograms in a given cloud-object size category. The results of statistical hypothesis tests using all three distances as test statistics are generally similar, indicating the validity of the proposed method. The Euclidean distance is determined to be most suitable after comparing the statistical tests of several parameters with distinct probability distributions among three cloud-object size categories. Impacts on the statistical significance levels resulting from differences in the total lengths of satellite footprint data between two size categories are also discussed.
New Statistics for Testing Differential Expression of Pathways from Microarray Data
NASA Astrophysics Data System (ADS)
Siu, Hoicheong; Dong, Hua; Jin, Li; Xiong, Momiao
Exploring biological meaning from microarray data is very important but remains a great challenge. Here, we developed three new statistics: linear combination test, quadratic test and de-correlation test to identify differentially expressed pathways from gene expression profile. We apply our statistics to two rheumatoid arthritis datasets. Notably, our results reveal three significant pathways and 275 genes in common in two datasets. The pathways we found are meaningful to uncover the disease mechanisms of rheumatoid arthritis, which implies that our statistics are a powerful tool in functional analysis of gene expression data.
Mnemonic Aids during Tests: Worthless Frivolity or Effective Tool in Statistics Education?
ERIC Educational Resources Information Center
Larwin, Karen H.; Larwin, David A.; Gorman, Jennifer
2012-01-01
Researchers have explored many pedagogical approaches in an effort to assist students in finding understanding and comfort in required statistics courses. This study investigates the impact of mnemonic aids used during tests on students' statistics course performance in particular. In addition, the present study explores several hypotheses that…
ERIC Educational Resources Information Center
LeMire, Steven D.
2010-01-01
This paper proposes an argument framework for the teaching of null hypothesis statistical testing and its application in support of research. Elements of the Toulmin (1958) model of argument are used to illustrate the use of p values and Type I and Type II error rates in support of claims about statistical parameters and subject matter research…
Development of Statistically Parallel Tests by Analysis of Unique Item Variance.
ERIC Educational Resources Information Center
Ree, Malcolm James
A method for developing statistically parallel tests based on the analysis of unique item variance was developed. A test population of 907 basic airmen trainees were required to estimate the angle at which an object in a photograph was viewed, selecting from eight possibilities. A FORTRAN program known as VARSEL was used to rank all the test items…
The Use of Person-Fit Statistics To Analyze Placement Tests.
ERIC Educational Resources Information Center
Dodeen, Hamzeh
Person fit is a statistical index that can be used as a direct measure to assess test accuracy by analyzing the response pattern of examinees and identifying those who misfit the testing model. This misfitting is a source of inaccuracy in estimating an individual's ability, and it decreases the expected criterion-related validity of the test being…
A Third Moment Adjusted Test Statistic for Small Sample Factor Analysis.
Lin, Johnny; Bentler, Peter M
2012-01-01
Goodness of fit testing in factor analysis is based on the assumption that the test statistic is asymptotically chi-square; but this property may not hold in small samples even when the factors and errors are normally distributed in the population. Robust methods such as Browne's asymptotically distribution-free method and Satorra Bentler's mean scaling statistic were developed under the presumption of non-normality in the factors and errors. This paper finds new application to the case where factors and errors are normally distributed in the population but the skewness of the obtained test statistic is still high due to sampling error in the observed indicators. An extension of Satorra Bentler's statistic is proposed that not only scales the mean but also adjusts the degrees of freedom based on the skewness of the obtained test statistic in order to improve its robustness under small samples. A simple simulation study shows that this third moment adjusted statistic asymptotically performs on par with previously proposed methods, and at a very small sample size offers superior Type I error rates under a properly specified model. Data from Mardia, Kent and Bibby's study of students tested for their ability in five content areas that were either open or closed book were used to illustrate the real-world performance of this statistic.
A General Class of Test Statistics for Van Valen’s Red Queen Hypothesis
Wiltshire, Jelani; Huffer, Fred W.; Parker, William C.
2014-01-01
Van Valen’s Red Queen hypothesis states that within a homogeneous taxonomic group the age is statistically independent of the rate of extinction. The case of the Red Queen hypothesis being addressed here is when the homogeneous taxonomic group is a group of similar species. Since Van Valen’s work, various statistical approaches have been used to address the relationship between taxon age and the rate of extinction. We propose a general class of test statistics that can be used to test for the effect of age on the rate of extinction. These test statistics allow for a varying background rate of extinction and attempt to remove the effects of other covariates when assessing the effect of age on extinction. No model is assumed for the covariate effects. Instead we control for covariate effects by pairing or grouping together similar species. Simulations are used to compare the power of the statistics. We apply the test statistics to data on Foram extinctions and find that age has a positive effect on the rate of extinction. A derivation of the null distribution of one of the test statistics is provided in the supplementary material. PMID:24910489
A General Class of Test Statistics for Van Valen's Red Queen Hypothesis.
Wiltshire, Jelani; Huffer, Fred W; Parker, William C
2014-09-01
Van Valen's Red Queen hypothesis states that within a homogeneous taxonomic group the age is statistically independent of the rate of extinction. The case of the Red Queen hypothesis being addressed here is when the homogeneous taxonomic group is a group of similar species. Since Van Valen's work, various statistical approaches have been used to address the relationship between taxon age and the rate of extinction. We propose a general class of test statistics that can be used to test for the effect of age on the rate of extinction. These test statistics allow for a varying background rate of extinction and attempt to remove the effects of other covariates when assessing the effect of age on extinction. No model is assumed for the covariate effects. Instead we control for covariate effects by pairing or grouping together similar species. Simulations are used to compare the power of the statistics. We apply the test statistics to data on Foram extinctions and find that age has a positive effect on the rate of extinction. A derivation of the null distribution of one of the test statistics is provided in the supplementary material.
Comment on the asymptotics of a distribution-free goodness of fit test statistic.
Browne, Michael W; Shapiro, Alexander
2015-03-01
In a recent article Jennrich and Satorra (Psychometrika 78: 545-552, 2013) showed that a proof by Browne (British Journal of Mathematical and Statistical Psychology 37: 62-83, 1984) of the asymptotic distribution of a goodness of fit test statistic is incomplete because it fails to prove that the orthogonal component function employed is continuous. Jennrich and Satorra (Psychometrika 78: 545-552, 2013) showed how Browne's proof can be completed satisfactorily but this required the development of an extensive and mathematically sophisticated framework for continuous orthogonal component functions. This short note provides a simple proof of the asymptotic distribution of Browne's (British Journal of Mathematical and Statistical Psychology 37: 62-83, 1984) test statistic by using an equivalent form of the statistic that does not involve orthogonal component functions and consequently avoids all complicating issues associated with them. PMID:24306556
Comment on the asymptotics of a distribution-free goodness of fit test statistic.
Browne, Michael W; Shapiro, Alexander
2015-03-01
In a recent article Jennrich and Satorra (Psychometrika 78: 545-552, 2013) showed that a proof by Browne (British Journal of Mathematical and Statistical Psychology 37: 62-83, 1984) of the asymptotic distribution of a goodness of fit test statistic is incomplete because it fails to prove that the orthogonal component function employed is continuous. Jennrich and Satorra (Psychometrika 78: 545-552, 2013) showed how Browne's proof can be completed satisfactorily but this required the development of an extensive and mathematically sophisticated framework for continuous orthogonal component functions. This short note provides a simple proof of the asymptotic distribution of Browne's (British Journal of Mathematical and Statistical Psychology 37: 62-83, 1984) test statistic by using an equivalent form of the statistic that does not involve orthogonal component functions and consequently avoids all complicating issues associated with them.
CUSUM-Based Person-Fit Statistics for Adaptive Testing. Research Report 99-05.
ERIC Educational Resources Information Center
van Krimpen-Stoop, Edith M. L. A.; Meijer, Rob R.
Item scores that do not fit an assumed item response theory model may cause the latent trait value to be estimated inaccurately. Several person-fit statistics for detecting nonfitting score patterns for paper-and-pencil tests have been proposed. In the context of computerized adaptive tests (CAT), the use of person-fit analysis has hardly been…
What Are Null Hypotheses? The Reasoning Linking Scientific and Statistical Hypothesis Testing
ERIC Educational Resources Information Center
Lawson, Anton E.
2008-01-01
We should dispense with use of the confusing term "null hypothesis" in educational research reports. To explain why the term should be dropped, the nature of, and relationship between, scientific and statistical hypothesis testing is clarified by explication of (a) the scientific reasoning used by Gregor Mendel in testing specific…
Evaluating Two Models of Collaborative Tests in an Online Introductory Statistics Course
ERIC Educational Resources Information Center
Björnsdóttir, Auðbjörg; Garfield, Joan; Everson, Michelle
2015-01-01
This study explored the use of two different types of collaborative tests in an online introductory statistics course. A study was designed and carried out to investigate three research questions: (1) What is the difference in students' learning between using consensus and non-consensus collaborative tests in the online environment?, (2) What is…
ERIC Educational Resources Information Center
White, Desley
2015-01-01
Two practical activities are described, which aim to support critical thinking about statistics as they concern multiple outcomes testing. Formulae are presented in Microsoft Excel spreadsheets, which are used to calculate the inflation of error associated with the quantity of tests performed. This is followed by a decision-making exercise, where…
A Note on Three Statistical Tests in the Logistic Regression DIF Procedure
ERIC Educational Resources Information Center
Paek, Insu
2012-01-01
Although logistic regression became one of the well-known methods in detecting differential item functioning (DIF), its three statistical tests, the Wald, likelihood ratio (LR), and score tests, which are readily available under the maximum likelihood, do not seem to be consistently distinguished in DIF literature. This paper provides a clarifying…
NASA Technical Reports Server (NTRS)
Keegan, W. B.
1974-01-01
In order to produce cost effective environmental test programs, the test specifications must be realistic and to be useful, they must be available early in the life of a program. This paper describes a method for achieving such specifications for subsystems by utilizing the results of a statistical analysis of data acquired at subsystem mounting locations during system level environmental tests. The paper describes the details of this statistical analysis. The resultant recommended levels are a function of the subsystems' mounting location in the spacecraft. Methods of determining this mounting 'zone' are described. Recommendations are then made as to which of the various problem areas encountered should be pursued further.
Steffen, Jason H.; Ford, Eric B.; Rowe, Jason F.; Fabrycky, Daniel C.; Holman, Matthew J.; Welsh, William F.; Borucki, William J.; Batalha, Natalie M.; Bryson, Steve; Caldwell, Douglas A.; Ciardi, David R.; /Caltech /NASA, Ames /SETI Inst., Mtn. View
2012-01-01
We analyze the deviations of transit times from a linear ephemeris for the Kepler Objects of Interest (KOI) through Quarter six (Q6) of science data. We conduct two statistical tests for all KOIs and a related statistical test for all pairs of KOIs in multi-transiting systems. These tests identify several systems which show potentially interesting transit timing variations (TTVs). Strong TTV systems have been valuable for the confirmation of planets and their mass measurements. Many of the systems identified in this study should prove fruitful for detailed TTV studies.
Improved Test Planning and Analysis Through the Use of Advanced Statistical Methods
NASA Technical Reports Server (NTRS)
Green, Lawrence L.; Maxwell, Katherine A.; Glass, David E.; Vaughn, Wallace L.; Barger, Weston; Cook, Mylan
2016-01-01
The goal of this work is, through computational simulations, to provide statistically-based evidence to convince the testing community that a distributed testing approach is superior to a clustered testing approach for most situations. For clustered testing, numerous, repeated test points are acquired at a limited number of test conditions. For distributed testing, only one or a few test points are requested at many different conditions. The statistical techniques of Analysis of Variance (ANOVA), Design of Experiments (DOE) and Response Surface Methods (RSM) are applied to enable distributed test planning, data analysis and test augmentation. The D-Optimal class of DOE is used to plan an optimally efficient single- and multi-factor test. The resulting simulated test data are analyzed via ANOVA and a parametric model is constructed using RSM. Finally, ANOVA can be used to plan a second round of testing to augment the existing data set with new data points. The use of these techniques is demonstrated through several illustrative examples. To date, many thousands of comparisons have been performed and the results strongly support the conclusion that the distributed testing approach outperforms the clustered testing approach.
Wang, Q.; Denton, D.L.; Shukla, R.
2000-01-01
As a follow up to the recommendations of the September 1995 SETAC Pellston Workshop on Whole Effluent Toxicity (WET) on test methods and appropriate endpoints, this paper will discuss the applications and statistical properties of using a statistical criterion of minimum significant difference (MSD). The authors examined the upper limits of acceptable MSDs as acceptance criterion in the case of normally distributed data. The implications of this approach are examined in terms of false negative rate as well as false positive rate. Results indicated that the proposed approach has reasonable statistical properties. Reproductive data from short-term chronic WET test with Ceriodaphnia dubia tests were used to demonstrate the applications of the proposed approach. The data were collected by the North Carolina Department of Environment, Health, and Natural Resources (Raleigh, NC, USA) as part of their National Pollutant Discharge Elimination System program.
Testing Hardy-Weinberg equilibrium with a simple root-mean-square statistic.
Ward, Rachel; Carroll, Raymond J
2014-01-01
We provide evidence that, in certain circumstances, a root-mean-square test of goodness of fit can be significantly more powerful than state-of-the-art tests in detecting deviations from Hardy-Weinberg equilibrium. Unlike Pearson's $\\chi ^2$ test, the log-likelihood-ratio test, and Fisher's exact test, which are sensitive to relative discrepancies between genotypic frequencies, the root-mean-square test is sensitive to absolute discrepancies. This can increase statistical power, as we demonstrate using benchmark data sets and simulations, and through asymptotic analysis.
Green, John; Wheeler, James R
2013-11-15
Solvents are often used to aid test item preparation in aquatic ecotoxicity experiments. This paper discusses the practical, statistical and regulatory considerations. The selection of the appropriate control (if a solvent is used) for statistical analysis is investigated using a database of 141 responses (endpoints) from 71 experiments. The advantages and disadvantages of basing the statistical analysis of treatment effects to the water control alone, solvent control alone, combined controls, or a conditional strategy of combining controls, when not statistically significantly different, are tested. The latter two approaches are shown to have distinct advantages. It is recommended that this approach continue to be the standard used for regulatory and research aquatic ecotoxicology studies. However, wherever technically feasible a solvent should not be employed or at least the concentration minimized.
Modified H-statistic with adaptive Winsorized mean in two groups test
NASA Astrophysics Data System (ADS)
Teh, Kian Wooi; Abdullah, Suhaida; Yahaya, Sharipah Soaad Syed; Yusof, Zahayu Md
2014-06-01
t-test is a commonly used test statistics when comparing two independent groups. The computation of this test is simple yet it is powerful under normal distribution and equal variance dataset. However, in real life data, sometimes it is hard to get dataset which has this package. The violation of assumptions (normality and equal variances) will give the devastating effect on the Type I error rate control to the t-test. On the same time, the statistical power also will be reduced. Therefore in this study, the adaptive Winsorised mean with hinge estimator in H-statistic (AWM-H) is proposed. The H-statistic is one of the robust statistics that able to handle the problem of nonnormality in comparing independent group. This procedure originally used Modified One-step M (MOM) estimator which employed trimming process. In the AWM-H procedure, the MOM estimator is replaced with the adaptive Winsorized mean (AWM) as the central tendency measure of the test. The Winsorization process is based on hinge estimator HQ or HQ1. Overall results showed that the proposed method performed better than the original method and the classical method especially under heavy tailed distribution.
Statistical studies of animal response data from USF toxicity screening test method
NASA Technical Reports Server (NTRS)
Hilado, C. J.; Machado, A. M.
1978-01-01
Statistical examination of animal response data obtained using Procedure B of the USF toxicity screening test method indicates that the data deviate only slightly from a normal or Gaussian distribution. This slight departure from normality is not expected to invalidate conclusions based on theoretical statistics. Comparison of times to staggering, convulsions, collapse, and death as endpoints shows that time to death appears to be the most reliable endpoint because it offers the lowest probability of missed observations and premature judgements.
A NEW TEST OF THE STATISTICAL NATURE OF THE BRIGHTEST CLUSTER GALAXIES
Lin, Yen-Ting; Ostriker, Jeremiah P.; Miller, Christopher J.
2010-06-01
A novel statistic is proposed to examine the hypothesis that all cluster galaxies are drawn from the same luminosity distribution (LD). In such a 'statistical model' of galaxy LD, the brightest cluster galaxies (BCGs) are simply the statistical extreme of the galaxy population. Using a large sample of nearby clusters, we show that BCGs in high luminosity clusters (e.g., L {sub tot} {approx}> 4 x 10{sup 11} h {sup -2} {sub 70} L {sub sun}) are unlikely (probability {<=}3 x 10{sup -4}) to be drawn from the LD defined by all red cluster galaxies more luminous than M{sub r} = -20. On the other hand, BCGs in less luminous clusters are consistent with being the statistical extreme. Applying our method to the second brightest galaxies, we show that they are consistent with being the statistical extreme, which implies that the BCGs are also distinct from non-BCG luminous, red, cluster galaxies. We point out some issues with the interpretation of the classical tests proposed by Tremaine and Richstone (TR) that are designed to examine the statistical nature of BCGs, investigate the robustness of both our statistical test and those of TR against difficulties in photometry of galaxies of large angular size, and discuss the implication of our findings on surveys that use the luminous red galaxies to measure the baryon acoustic oscillation features in the galaxy power spectrum.
Statistical tests, P values, confidence intervals, and power: a guide to misinterpretations.
Greenland, Sander; Senn, Stephen J; Rothman, Kenneth J; Carlin, John B; Poole, Charles; Goodman, Steven N; Altman, Douglas G
2016-04-01
Misinterpretation and abuse of statistical tests, confidence intervals, and statistical power have been decried for decades, yet remain rampant. A key problem is that there are no interpretations of these concepts that are at once simple, intuitive, correct, and foolproof. Instead, correct use and interpretation of these statistics requires an attention to detail which seems to tax the patience of working scientists. This high cognitive demand has led to an epidemic of shortcut definitions and interpretations that are simply wrong, sometimes disastrously so-and yet these misinterpretations dominate much of the scientific literature. In light of this problem, we provide definitions and a discussion of basic statistics that are more general and critical than typically found in traditional introductory expositions. Our goal is to provide a resource for instructors, researchers, and consumers of statistics whose knowledge of statistical theory and technique may be limited but who wish to avoid and spot misinterpretations. We emphasize how violation of often unstated analysis protocols (such as selecting analyses for presentation based on the P values they produce) can lead to small P values even if the declared test hypothesis is correct, and can lead to large P values even if that hypothesis is incorrect. We then provide an explanatory list of 25 misinterpretations of P values, confidence intervals, and power. We conclude with guidelines for improving statistical interpretation and reporting. PMID:27209009
NASA Astrophysics Data System (ADS)
Woessner, J.; Schorlemmer, D.; Wiemer, S.; Mai, P. M.
2005-12-01
Quantitatively correlating properties of finite-fault source models with hypocenters of aftershocks may provide new insight in the relationship between either slip or static stress change distributions and aftershock occurrence. We present advanced non-standard statistical test approaches to evaluate the test hypotheses (1) if aftershocks are preferentially located in areas of low slip and (2) if aftershocks are located in increased shear stress against the null hypothesis: aftershocks are located randomly on the fault plane. By using multiple test approaches, we investigate possible pitfalls and the information content of statistical testing. To perform the tests, we use earthquakes for which multiple finite-fault source models and earthquake catalogs of varying accuracy exist. The aftershock hypocenters are projected onto the main-shock rupture plane and uncertainties are accounted for by simulating hypocenter locations in the given error bounds. For the statistical tests, we retain the spatial clustering of earthquakes as the most important observed features of seismicity and synthesize random slip distributions with different approaches: first, using standard statistical methods that randomize the obtained finite-fault source model values and second, using a random spatial field model. We then determine the number of aftershocks in low-slip or increased shear-stress regions for simulated slip distributions, and compare those to the measurements obtained for finite-source slip inversions. We apply the tests to prominent earthquakes in California and Japan and find statistical significant evidence that aftershocks are preferentially located in low-slip regions. The tests, however, show a lower significance for the correlation with the shear-stress distribution, but are in general agreement with the expectations of the asperity model. Tests using the hypocenters of relocated catalogs show higher significances.
Statistical hypothesis testing by weak-value amplification: Proposal and evaluation
NASA Astrophysics Data System (ADS)
Susa, Yuki; Tanaka, Saki
2015-07-01
We study the detection capability of the weak-value amplification on the basis of the statistical hypothesis testing. We propose a reasonable testing method in the physical and statistical senses to find that the weak measurement with the large weak value has the advantage to increase the detection power and to reduce the possibility of missing the presence of interaction. We enhance the physical understanding of the weak value and mathematically establish the significance of the weak-value amplification. Our present work overcomes the critical dilemma of the weak-value amplification that the larger the amplification is, the smaller the number of data becomes, because the statistical hypothesis testing works even for a small number of data. This is contrasted with the parameter estimation by the weak-value amplification in the literature which requires a large number of data.
Festing, Michael F W
2014-12-01
The results of repeat-dose toxicity tests are usually presented as tables of means and standard deviations (SDs), with an indication of statistical significance for each biomarker. Interpretation is based mainly on the pattern of statistical significance rather than the magnitude of any response. Multiple statistical testing of many biomarkers leads to false-positive results and, with the exception of growth data, few graphical methods for showing the results are available. By converting means and SDs to standardized effect sizes, a range of graphical techniques including dot plots, line plots, box plots, and quantile-quantile plots become available to show the patterns of response. A bootstrap statistical test involving all biomarkers is proposed to compare the magnitudes of the response between treated groups. These methods are proposed as an extension rather than an alternative to current statistical analyses. They can be applied to published work retrospectively, as all that is required is tables of means and SDs. The methods are illustrated using published articles, where the results range from strong positive to completely negative responses to the test substances.
New advances in methodology for statistical tests useful in geostatistical studies
Borgman, L.E.
1988-05-01
Methodology for statistical procedures to perform tests of hypothesis pertaining to various aspects of geostatistical investigations has been slow in developing. The correlated nature of the data precludes most classical tests and makes the design of new tests difficult. Recent studies have led to modifications of the classical t test which allow for the intercorrelation. In addition, results for certain nonparametric tests have been obtained. The conclusions of these studies provide a variety of new tools for the geostatistician in deciding questions on significant differences and magnitudes.
Miranda de Sá, Antonio Mauricio F L; Infantosi, Antonio Fernando C; Lazarev, Vladimir V
2007-01-01
In the present work, a commonly used index for evaluating the Event-Related Synchronization and Desynchronization (ERS/ERD) in the EEG was expressed as a function of the Spectral F-Test (SFT), which is a statistical test for assessing if two sample spectra are from populations with identical theoretical spectra. The sampling distribution of SFT has been derived, allowing hence ERS/ERD to be evaluated under a statistical basis. An example of the technique was also provided in the EEG signals from 10 normal subjects during intermittent photic stimulation.
Testing independence of bivariate interval-censored data using modified Kendall's tau statistic.
Kim, Yuneung; Lim, Johan; Park, DoHwan
2015-11-01
In this paper, we study a nonparametric procedure to test independence of bivariate interval censored data; for both current status data (case 1 interval-censored data) and case 2 interval-censored data. To do it, we propose a score-based modification of the Kendall's tau statistic for bivariate interval-censored data. Our modification defines the Kendall's tau statistic with expected numbers of concordant and disconcordant pairs of data. The performance of the modified approach is illustrated by simulation studies and application to the AIDS study. We compare our method to alternative approaches such as the two-stage estimation method by Sun et al. (Scandinavian Journal of Statistics, 2006) and the multiple imputation method by Betensky and Finkelstein (Statistics in Medicine, 1999b).
Variability-aware compact modeling and statistical circuit validation on SRAM test array
NASA Astrophysics Data System (ADS)
Qiao, Ying; Spanos, Costas J.
2016-03-01
Variability modeling at the compact transistor model level can enable statistically optimized designs in view of limitations imposed by the fabrication technology. In this work we propose a variability-aware compact model characterization methodology based on stepwise parameter selection. Transistor I-V measurements are obtained from bit transistor accessible SRAM test array fabricated using a collaborating foundry's 28nm FDSOI technology. Our in-house customized Monte Carlo simulation bench can incorporate these statistical compact models; and simulation results on SRAM writability performance are very close to measurements in distribution estimation. Our proposed statistical compact model parameter extraction methodology also has the potential of predicting non-Gaussian behavior in statistical circuit performances through mixtures of Gaussian distributions.
NASA Technical Reports Server (NTRS)
Colvin, E. L.; Emptage, M. R.
1992-01-01
The breaking load test provides quantitative stress corrosion cracking data by determining the residual strength of tension specimens that have been exposed to corrosive environments. Eight laboratories have participated in a cooperative test program under the auspices of ASTM Committee G-1 to evaluate the new test method. All eight laboratories were able to distinguish between three tempers of aluminum alloy 7075. The statistical analysis procedures that were used in the test program do not work well in all situations. An alternative procedure using Box-Cox transformations shows a great deal of promise. An ASTM standard method has been drafted which incorporates the Box-Cox procedure.
Candini, Giancarlo
2004-12-01
In the fields of didactics and continuous professional development (CPD) plans, the increasing use of multiple answer tests for the evaluation of the level of knowledge in various kinds of subjects makes it increasingly important to have reliable and effective tools for data processing and for the evaluation of the results. The aim of the present work is to explore a new methodological approach based on a widely tested statistical analysis able to yield more information content when compared with the traditional methods. With this purpose we suggest a Graduated Response Test and the relative operating characteristic curve (ROC) for the evaluation of the results. A short description of a computerized procedure, written in Visual Basic Pro (v.6.0), which automatically performs the statistical analysis, the ROC curves plot and the calculation of a learning index is given as well. PMID:15518651
ERIC Educational Resources Information Center
Dorman, Jeffrey P.
2009-01-01
This article discusses the effect of clustering on statistical tests conducted with school environment data. Because most school environment studies involve the collection of data from teachers nested within schools, the hierarchical nature to these data cannot be ignored. In particular, this article considers the influence of intraschool…
The Effect of Clustering on Statistical Tests: An Illustration Using Classroom Environment Data
ERIC Educational Resources Information Center
Dorman, Jeffrey Paul
2008-01-01
This paper discusses the effect of clustering on statistical tests and illustrates this effect using classroom environment data. Most classroom environment studies involve the collection of data from students nested within classrooms and the hierarchical nature to these data cannot be ignored. In particular, this paper studies the influence of…
A Critique of One-Tailed Hypothesis Test Procedures in Business and Economics Statistics Textbooks.
ERIC Educational Resources Information Center
Liu, Tung; Stone, Courtenay C.
1999-01-01
Surveys introductory business and economics statistics textbooks and finds that they differ over the best way to explain one-tailed hypothesis tests: the simple null-hypothesis approach or the composite null-hypothesis approach. Argues that the composite null-hypothesis approach contains methodological shortcomings that make it more difficult for…
ERIC Educational Resources Information Center
Ho, Andrew D.; Yu, Carol C.
2015-01-01
Many statistical analyses benefit from the assumption that unconditional or conditional distributions are continuous and normal. More than 50 years ago in this journal, Lord and Cook chronicled departures from normality in educational tests, and Micerri similarly showed that the normality assumption is met rarely in educational and psychological…
Connecting q-mutator theory with experimental tests of the spin-statistics connection
NASA Astrophysics Data System (ADS)
Hilborn, Robert C.
2000-11-01
The q-mutator theory is used to connect the value of 1-|q|, the parameter measuring the "difference" between quons and ordinary bosons and fermions, to experiments that test the spin-statistics connection. Such calculations are best carried out using a density matrix formulation because a superselection rule prevents transitions between states associated with different representations of the permutation group. The interpretation of the experimental results, however, in terms of a quantitative limit on 1-|q| can be easily misled by the density matrix formulation. As a concrete example, the theory is applied to a spin-statistics test for photons. The formalism is then applied to spin-statistics tests for electrons in atomic helium and for 16O nuclei in molecules. Finally, the analysis is used to extend experimental limits on composite systems such as 16O nuclei to provide a test of the spin-statistics connection for the constituents of those composite systems (nucleons and quarks in the case of oxygen nuclei).
Interpreting Statistical Significance Test Results: A Proposed New "What If" Method.
ERIC Educational Resources Information Center
Kieffer, Kevin M.; Thompson, Bruce
As the 1994 publication manual of the American Psychological Association emphasized, "p" values are affected by sample size. As a result, it can be helpful to interpret the results of statistical significant tests in a sample size context by conducting so-called "what if" analyses. However, these methods can be inaccurate unless "corrected" effect…
Recent Literature on Whether Statistical Significance Tests Should or Should Not Be Banned.
ERIC Educational Resources Information Center
Deegear, James
This paper summarizes the literature regarding statistical significant testing with an emphasis on recent literature in various discipline and literature exploring why researchers have demonstrably failed to be influenced by the American Psychological Association publication manual's encouragement to report effect sizes. Also considered are…
Connecting Science and Mathematics: The Nature of Scientific and Statistical Hypothesis Testing
ERIC Educational Resources Information Center
Lawson, Anton E.; Oehrtman, Michael; Jensen, Jamie
2008-01-01
Confusion persists concerning the roles played by scientific hypotheses and predictions in doing science. This confusion extends to the nature of scientific and statistical hypothesis testing. The present paper utilizes the "If/and/then/Therefore" pattern of hypothetico-deductive (HD) reasoning to explicate the nature of both scientific and…
Fine Mapping Causal Variants with an Approximate Bayesian Method Using Marginal Test Statistics.
Chen, Wenan; Larrabee, Beth R; Ovsyannikova, Inna G; Kennedy, Richard B; Haralambieva, Iana H; Poland, Gregory A; Schaid, Daniel J
2015-07-01
Two recently developed fine-mapping methods, CAVIAR and PAINTOR, demonstrate better performance over other fine-mapping methods. They also have the advantage of using only the marginal test statistics and the correlation among SNPs. Both methods leverage the fact that the marginal test statistics asymptotically follow a multivariate normal distribution and are likelihood based. However, their relationship with Bayesian fine mapping, such as BIMBAM, is not clear. In this study, we first show that CAVIAR and BIMBAM are actually approximately equivalent to each other. This leads to a fine-mapping method using marginal test statistics in the Bayesian framework, which we call CAVIAR Bayes factor (CAVIARBF). Another advantage of the Bayesian framework is that it can answer both association and fine-mapping questions. We also used simulations to compare CAVIARBF with other methods under different numbers of causal variants. The results showed that both CAVIARBF and BIMBAM have better performance than PAINTOR and other methods. Compared to BIMBAM, CAVIARBF has the advantage of using only marginal test statistics and takes about one-quarter to one-fifth of the running time. We applied different methods on two independent cohorts of the same phenotype. Results showed that CAVIARBF, BIMBAM, and PAINTOR selected the same top 3 SNPs; however, CAVIARBF and BIMBAM had better consistency in selecting the top 10 ranked SNPs between the two cohorts. Software is available at https://bitbucket.org/Wenan/caviarbf.
Identifying Local Dependence with a Score Test Statistic Based on the Bifactor Logistic Model
ERIC Educational Resources Information Center
Liu, Yang; Thissen, David
2012-01-01
Local dependence (LD) refers to the violation of the local independence assumption of most item response models. Statistics that indicate LD between a pair of items on a test or questionnaire that is being fitted with an item response model can play a useful diagnostic role in applications of item response theory. In this article, a new score test…
An Application of M[subscript 2] Statistic to Evaluate the Fit of Cognitive Diagnostic Models
ERIC Educational Resources Information Center
Liu, Yanlou; Tian, Wei; Xin, Tao
2016-01-01
The fit of cognitive diagnostic models (CDMs) to response data needs to be evaluated, since CDMs might yield misleading results when they do not fit the data well. Limited-information statistic M[subscript 2] and the associated root mean square error of approximation (RMSEA[subscript 2]) in item factor analysis were extended to evaluate the fit of…
Detecting trends in raptor counts: power and type I error rates of various statistical tests
Hatfield, J.S.; Gould, W.R.; Hoover, B.A.; Fuller, M.R.; Lindquist, E.L.
1996-01-01
We conducted simulations that estimated power and type I error rates of statistical tests for detecting trends in raptor population count data collected from a single monitoring site. Results of the simulations were used to help analyze count data of bald eagles (Haliaeetus leucocephalus) from 7 national forests in Michigan, Minnesota, and Wisconsin during 1980-1989. Seven statistical tests were evaluated, including simple linear regression on the log scale and linear regression with a permutation test. Using 1,000 replications each, we simulated n = 10 and n = 50 years of count data and trends ranging from -5 to 5% change/year. We evaluated the tests at 3 critical levels (alpha = 0.01, 0.05, and 0.10) for both upper- and lower-tailed tests. Exponential count data were simulated by adding sampling error with a coefficient of variation of 40% from either a log-normal or autocorrelated log-normal distribution. Not surprisingly, tests performed with 50 years of data were much more powerful than tests with 10 years of data. Positive autocorrelation inflated alpha-levels upward from their nominal levels, making the tests less conservative and more likely to reject the null hypothesis of no trend. Of the tests studied, Cox and Stuart's test and Pollard's test clearly had lower power than the others. Surprisingly, the linear regression t-test, Collins' linear regression permutation test, and the nonparametric Lehmann's and Mann's tests all had similar power in our simulations. Analyses of the count data suggested that bald eagles had increasing trends on at least 2 of the 7 national forests during 1980-1989.
NASA Astrophysics Data System (ADS)
Coelho, Carlos A.; Marques, Filipe J.
2013-09-01
In this paper the authors combine the equicorrelation and equivariance test introduced by Wilks [13] with the likelihood ratio test (l.r.t.) for independence of groups of variables to obtain the l.r.t. of block equicorrelation and equivariance. This test or its single block version may find applications in many areas as in psychology, education, medicine, genetics and they are important "in many tests of multivariate analysis, e.g. in MANOVA, Profile Analysis, Growth Curve analysis, etc" [12, 9]. By decomposing the overall hypothesis into the hypotheses of independence of groups of variables and the hypothesis of equicorrelation and equivariance we are able to obtain the expressions for the overall l.r.t. statistic and its moments. From these we obtain a suitable factorization of the characteristic function (c.f.) of the logarithm of the l.r.t. statistic, which enables us to develop highly manageable and precise near-exact distributions for the test statistic.
Rudd, James; Moore, Jason H; Urbanowicz, Ryan J
2013-11-01
Permutation-based statistics for evaluating the significance of class prediction, predictive attributes, and patterns of association have only appeared within the learning classifier system (LCS) literature since 2012. While still not widely utilized by the LCS research community, formal evaluations of test statistic confidence are imperative to large and complex real world applications such as genetic epidemiology where it is standard practice to quantify the likelihood that a seemingly meaningful statistic could have been obtained purely by chance. LCS algorithms are relatively computationally expensive on their own. The compounding requirements for generating permutation-based statistics may be a limiting factor for some researchers interested in applying LCS algorithms to real world problems. Technology has made LCS parallelization strategies more accessible and thus more popular in recent years. In the present study we examine the benefits of externally parallelizing a series of independent LCS runs such that permutation testing with cross validation becomes more feasible to complete on a single multi-core workstation. We test our python implementation of this strategy in the context of a simulated complex genetic epidemiological data mining problem. Our evaluations indicate that as long as the number of concurrent processes does not exceed the number of CPU cores, the speedup achieved is approximately linear. PMID:24358057
Schoenberg, Mike R; Dawson, Kyra A; Duff, Kevin; Patton, Doyle; Scott, James G; Adams, Russell L
2006-10-01
The Rey Auditory Verbal Learning Test [RAVLT; Rey, A. (1941). L'examen psychologique dans les cas d'encéphalopathie traumatique. Archives de Psychologie, 28, 21] is a commonly used neuropsychological measure that assesses verbal learning and memory. Normative data have been compiled [Schmidt, M. (1996). Rey Auditory and Verbal Learning Test: A handbook. Los Angeles, CA: Western Psychological Services]. When assessing an individual suspected of neurological dysfunction, useful comparisons include the extent that the patient deviates from healthy peers and also how closely the subject's performance matches those with known brain injury. This study provides the means and S.D.'s of 392 individuals with documented neurological dysfunction [closed head TBI (n=68), neoplasms (n=57), stroke (n=47), Dementia of the Alzheimer's type (n=158), and presurgical epilepsy left seizure focus (n=28), presurgical epilepsy right seizure focus (n=34)] and 122 patients with no known neurological dysfunction and psychiatric complaints. Patients were stratified into three age groups, 16-35, 36-59, and 60-88. Data were provided for trials I-V, List B, immediate recall, 30-min delayed recall, and recognition. Classification characteristics of the RAVLT using [Schmidt, M. (1996). Rey Auditory and Verbal Learning Test: A handbook. Los Angeles, CA: Western Psychological Services] meta-norms found the RAVLT to best distinguish patients suspected of Alzheimer's disease from the psychiatric comparison group. PMID:16987634
Comparison of statistical tests for group differences in brain functional networks.
Kim, Junghi; Wozniak, Jeffrey R; Mueller, Bryon A; Shen, Xiaotong; Pan, Wei
2014-11-01
Brain functional connectivity has been studied by analyzing time series correlations in regional brain activities based on resting-state fMRI data. Brain functional connectivity can be depicted as a network or graph defined as a set of nodes linked by edges. Nodes represent brain regions and an edge measures the strength of functional correlation between two regions. Most of existing work focuses on estimation of such a network. A key but inadequately addressed question is how to test for possible differences of the networks between two subject groups, say between healthy controls and patients. Here we illustrate and compare the performance of several state-of-the-art statistical tests drawn from the neuroimaging, genetics, ecology and high-dimensional data literatures. Both real and simulated data were used to evaluate the methods. We found that Network Based Statistic (NBS) performed well in many but not all situations, and its performance critically depends on the choice of its threshold parameter, which is unknown and difficult to choose in practice. Importantly, two adaptive statistical tests called adaptive sum of powered score (aSPU) and its weighted version (aSPUw) are easy to use and complementary to NBS, being higher powered than NBS in some situations. The aSPU and aSPUw tests can also be applied to adjust for covariates. Between the aSPU and aSPUw tests, they often, but not always, performed similarly with neither one as a uniform winner. On the other hand, Multivariate Matrix Distance Regression (MDMR) has been applied to detect group differences for brain connectivity; with the usual choice of the Euclidean distance, MDMR is a special case of the aSPU test. Consequently NBS, aSPU and aSPUw tests are recommended to test for group differences in functional connectivity. PMID:25086298
Application of a generalized likelihood ratio test statistic to MAGIC data
NASA Astrophysics Data System (ADS)
Klepser, S.; Krause, J.; Sitarek, J.; MAGIC Collaboration
2012-12-01
The commonly used detection test statistic for Cherenkov telescope data is Li & Ma (1983), Eq. 17. It evaluates the compatibility of event counts in an on-source region with those in a representative off-region. It does not exploit the typically known gamma-ray point spread function (PSF) of a system, and in practice its application requires either assumptions on the symmetry of the acceptance across the field of view, or Monte Carlo simulations. MAGIC has an azimuth-dependent, asymmetric acceptance which required a careful review of detection statistics. Besides an adapted Li & Ma based technique, the recently presented generalized LRT statistic of [1] is now in use. It is more flexible, more sensitive and less systematics-affected, because it is highly customized for multi-pointing Cherenkov telescope data with a known PSF. We present the application of this new method to archival MAGIC data and compare it to the other, Li&Ma-based method.
An Adaptive Association Test for Multiple Phenotypes with GWAS Summary Statistics.
Kim, Junghi; Bai, Yun; Pan, Wei
2015-12-01
We study the problem of testing for single marker-multiple phenotype associations based on genome-wide association study (GWAS) summary statistics without access to individual-level genotype and phenotype data. For most published GWASs, because obtaining summary data is substantially easier than accessing individual-level phenotype and genotype data, while often multiple correlated traits have been collected, the problem studied here has become increasingly important. We propose a powerful adaptive test and compare its performance with some existing tests. We illustrate its applications to analyses of a meta-analyzed GWAS dataset with three blood lipid traits and another with sex-stratified anthropometric traits, and further demonstrate its potential power gain over some existing methods through realistic simulation studies. We start from the situation with only one set of (possibly meta-analyzed) genome-wide summary statistics, then extend the method to meta-analysis of multiple sets of genome-wide summary statistics, each from one GWAS. We expect the proposed test to be useful in practice as more powerful than or complementary to existing methods.
Using global statistical tests in long-term Parkinson's disease clinical trials.
Huang, Peng; Goetz, Christopher G; Woolson, Robert F; Tilley, Barbara; Kerr, Douglas; Palesch, Yuko; Elm, Jordan; Ravina, Bernard; Bergmann, Kenneth J; Kieburtz, Karl
2009-09-15
Parkinson's disease (PD) impairments are multidimensional, making it difficult to choose a single primary outcome when evaluating treatments to stop or lessen the long-term decline in PD. We review commonly used multivariate statistical methods for assessing a treatment's global impact, and we highlight the novel Global Statistical Test (GST) methodology. We compare the GST to other multivariate approaches using data from two PD trials. In one trial where the treatment showed consistent improvement on all primary and secondary outcomes, the GST was more powerful than other methods in demonstrating significant improvement. In the trial where treatment induced both improvement and deterioration in key outcomes, the GST failed to demonstrate statistical evidence even though other techniques showed significant improvement. Based on the statistical properties of the GST and its relevance to overall treatment benefit, the GST appears particularly well suited for a disease like PD where disability and impairment reflect dysfunction of diverse brain systems and where both disease and treatment side effects impact quality of life. In future long term trials, use of GST for primary statistical analysis would allow the assessment of clinically relevant outcomes rather than the artificial selection of a single primary outcome.
Jenkinson, Garrett; Goutsias, John
2013-05-28
The master equation is used extensively to model chemical reaction systems with stochastic dynamics. However, and despite its phenomenological simplicity, it is not in general possible to compute the solution of this equation. Drawing exact samples from the master equation is possible, but can be computationally demanding, especially when estimating high-order statistical summaries or joint probability distributions. As a consequence, one often relies on analytical approximations to the solution of the master equation or on computational techniques that draw approximative samples from this equation. Unfortunately, it is not in general possible to check whether a particular approximation scheme is valid. The main objective of this paper is to develop an effective methodology to address this problem based on statistical hypothesis testing. By drawing a moderate number of samples from the master equation, the proposed techniques use the well-known Kolmogorov-Smirnov statistic to reject the validity of a given approximation method or accept it with a certain level of confidence. Our approach is general enough to deal with any master equation and can be used to test the validity of any analytical approximation method or any approximative sampling technique of interest. A number of examples, based on the Schlögl model of chemistry and the SIR model of epidemiology, clearly illustrate the effectiveness and potential of the proposed statistical framework.
Rivoirard, Romain; Duplay, Vianney; Oriol, Mathieu; Tinquaut, Fabien; Chauvin, Franck; Magne, Nicolas; Bourmaud, Aurelie
2016-01-01
Background Quality of reporting for Randomized Clinical Trials (RCTs) in oncology was analyzed in several systematic reviews, but, in this setting, there is paucity of data for the outcomes definitions and consistency of reporting for statistical tests in RCTs and Observational Studies (OBS). The objective of this review was to describe those two reporting aspects, for OBS and RCTs in oncology. Methods From a list of 19 medical journals, three were retained for analysis, after a random selection: British Medical Journal (BMJ), Annals of Oncology (AoO) and British Journal of Cancer (BJC). All original articles published between March 2009 and March 2014 were screened. Only studies whose main outcome was accompanied by a corresponding statistical test were included in the analysis. Studies based on censored data were excluded. Primary outcome was to assess quality of reporting for description of primary outcome measure in RCTs and of variables of interest in OBS. A logistic regression was performed to identify covariates of studies potentially associated with concordance of tests between Methods and Results parts. Results 826 studies were included in the review, and 698 were OBS. Variables were described in Methods section for all OBS studies and primary endpoint was clearly detailed in Methods section for 109 RCTs (85.2%). 295 OBS (42.2%) and 43 RCTs (33.6%) had perfect agreement for reported statistical test between Methods and Results parts. In multivariable analysis, variable "number of included patients in study" was associated with test consistency: aOR (adjusted Odds Ratio) for third group compared to first group was equal to: aOR Grp3 = 0.52 [0.31–0.89] (P value = 0.009). Conclusion Variables in OBS and primary endpoint in RCTs are reported and described with a high frequency. However, statistical tests consistency between methods and Results sections of OBS is not always noted. Therefore, we encourage authors and peer reviewers to verify consistency of
Portmanteau test statistics for seasonal serial correlation in time series models.
Mahdi, Esam
2016-01-01
The seasonal autoregressive moving average SARMA models have been widely adopted for modeling many time series encountered in economic, hydrology, meteorological, and environmental studies which exhibited strong seasonal behavior with a period s. If the model is adequate, the autocorrelations in the errors at the seasonal and the nonseasonal lags will be zero. Despite the popularity uses of the portmanteau tests for the SARMA models, the diagnostic checking at the seasonal lags [Formula: see text], where m is the largest lag considered for autocorrelation and s is the seasonal period, has not yet received as much attention as it deserves. In this paper, we devise seasonal portmanteau test statistics to test whether the seasonal autocorrelations at multiple lags s of time series are different from zero. Simulation studies are performed to assess the performance of the asymptotic distribution results of the proposed statistics in finite samples. Results suggest to use the proposed tests as complementary to those classical tests found in literature. An illustrative application is given to demonstrate the usefulness of this test. PMID:27652059
2014-01-01
Background Under a Markov model of evolution, recoding, or lumping, of the four nucleotides into fewer groups may permit analysis under simpler conditions but may unfortunately yield misleading results unless the evolutionary process of the recoded groups remains Markovian. If a Markov process is lumpable, then the evolutionary process of the recoded groups is Markovian. Results We consider stationary, reversible, and homogeneous Markov processes on two taxa and compare three tests for lumpability: one using an ad hoc test statistic, which is based on an index that is evaluated using a bootstrap approximation of its distribution; one that is based on a test proposed specifically for Markov chains; and one using a likelihood-ratio test. We show that the likelihood-ratio test is more powerful than the index test, which is more powerful than that based on the Markov chain test statistic. We also show that for stationary processes on binary trees with more than two taxa, the tests can be applied to all pairs. Finally, we show that if the process is lumpable, then estimates obtained under the recoded model agree with estimates obtained under the original model, whereas, if the process is not lumpable, then these estimates can differ substantially. We apply the new likelihood-ratio test for lumpability to two primate data sets, one with a mitochondrial origin and one with a nuclear origin. Conclusions Recoding may result in biased phylogenetic estimates because the original evolutionary process is not lumpable. Accordingly, testing for lumpability should be done prior to phylogenetic analysis of recoded data. PMID:24564837
Beckstead, Jason W
2013-10-01
This is the second in a short series of papers on measurement theory and practice with particular relevance to intervention research in nursing, midwifery, and healthcare. This paper begins with an illustration of how random measurement error decreases the power of statistical tests and a review of the roles of sample size and effect size in hypothesis testing. A simple formula is presented and discussed for calculating sample size during the planning stages of intervention studies. Finally, an approach for incorporating reliability estimates into a priori power analyses is introduced and illustrated with a practical example. The approach permits researchers to compare alternative study designs, in terms of their statistical power. An SPSS program is provided to facilitate this approach and to assist researchers in making optimal decisions when choosing among alternative study designs.
Taroni, F; Biedermann, A; Bozza, S
2016-02-01
Many people regard the concept of hypothesis testing as fundamental to inferential statistics. Various schools of thought, in particular frequentist and Bayesian, have promoted radically different solutions for taking a decision about the plausibility of competing hypotheses. Comprehensive philosophical comparisons about their advantages and drawbacks are widely available and continue to span over large debates in the literature. More recently, controversial discussion was initiated by an editorial decision of a scientific journal [1] to refuse any paper submitted for publication containing null hypothesis testing procedures. Since the large majority of papers published in forensic journals propose the evaluation of statistical evidence based on the so called p-values, it is of interest to expose the discussion of this journal's decision within the forensic science community. This paper aims to provide forensic science researchers with a primer on the main concepts and their implications for making informed methodological choices.
Statistical correlation analysis for comparing vibration data from test and analysis
NASA Technical Reports Server (NTRS)
Butler, T. G.; Strang, R. F.; Purves, L. R.; Hershfeld, D. J.
1986-01-01
A theory was developed to compare vibration modes obtained by NASTRAN analysis with those obtained experimentally. Because many more analytical modes can be obtained than experimental modes, the analytical set was treated as expansion functions for putting both sources in comparative form. The dimensional symmetry was developed for three general cases: nonsymmetric whole model compared with a nonsymmetric whole structural test, symmetric analytical portion compared with a symmetric experimental portion, and analytical symmetric portion with a whole experimental test. The theory was coded and a statistical correlation program was installed as a utility. The theory is established with small classical structures.
NASA Astrophysics Data System (ADS)
Haam, E. K.; Huybers, P.
2008-12-01
To understand the Earth's climate, we must understand the inter-relations between its specific geographical areas which, in the case of paleoclimatology, can be profitably undertaken from an empirical perspective. However, assessment of the inter-relation between separate paleoclimate records is inevitably hindered by uncertainties in the absolute and relative age/dating of these climate records, because the correlation between two paleoclimate data with age uncertainty can change dramatically when variations of the age are allowed within the uncertainty limit. Through rigorous statistical analysis of the available proxy data, we can hope to gain better insight into the nature and scope of the mechanisms governing their variability. We propose a statistical algorithm to test for the presence of correlation between two paleoclimate time series with age/dating uncertainties. Previous works in this area have focused on searching for the maximum similarity out of all possible realizations of the series, either heuristically (visual wiggle matching) or through more quantitative methods (eg. cross-correlation maximizer, dynamic programming). In contrast, this algorithm seeks to determine the statistical significance of the maximum covariance. The probability of obtaining a certain maximum covariance from purely random events can provide us with an objective standard for real correlation and it is assessed using the theory of extreme order statistics, as a multivariate normal integral. Since there is no known closed form solution for a multivariate normal integral, a numerical method is used. We apply this algorithm to test for the correlation of the Dansgaard-Oeschger variability observed during MIS3 in the GISPII ice core and millennial variability recorded at cites including Botuvera Cave in Brazil, Hulu Cave in China, Eastern Indonesia, the Arabian Sea, Villa Cave in Europe, New Zealand and the Santa Barbara basin. Results of the analysis are presented as a map of the
Case Studies for the Statistical Design of Experiments Applied to Powered Rotor Wind Tunnel Tests
NASA Technical Reports Server (NTRS)
Overmeyer, Austin D.; Tanner, Philip E.; Martin, Preston B.; Commo, Sean A.
2015-01-01
The application of statistical Design of Experiments (DOE) to helicopter wind tunnel testing was explored during two powered rotor wind tunnel entries during the summers of 2012 and 2013. These tests were performed jointly by the U.S. Army Aviation Development Directorate Joint Research Program Office and NASA Rotary Wing Project Office, currently the Revolutionary Vertical Lift Project, at NASA Langley Research Center located in Hampton, Virginia. Both entries were conducted in the 14- by 22-Foot Subsonic Tunnel with a small portion of the overall tests devoted to developing case studies of the DOE approach as it applies to powered rotor testing. A 16-47 times reduction in the number of data points required was estimated by comparing the DOE approach to conventional testing methods. The average error for the DOE surface response model for the OH-58F test was 0.95 percent and 4.06 percent for drag and download, respectively. The DOE surface response model of the Active Flow Control test captured the drag within 4.1 percent of measured data. The operational differences between the two testing approaches are identified, but did not prevent the safe operation of the powered rotor model throughout the DOE test matrices.
ERIC Educational Resources Information Center
Weigle, David C.
The purposes of the present paper are to address the historical development of statistical significance testing and to briefly examine contemporary practices regarding such testing in the light of these historical origins. Precursors leading to the advent of statistical significance testing are examined as are more recent controversies surrounding…
Symmetry of the CMB sky as a new test of its statistical isotropy. Non cosmological octupole?
Naselsky, P.; Hansen, M.; Kim, J. E-mail: kirstejn@nbi.dk
2011-09-01
In this article we propose a novel test for statistical anisotropy of the CMB ΔT( n-circumflex = (θ,φ)). The test is based on the fact, that the Galactic foregrounds have a remarkably strong symmetry with respect to their antipodal points with respect to the Galactic plane, while the cosmological signal should not be symmetric or asymmetric under these transitions. We have applied the test for the octupole component of the WMAP ILC 7 map, by looking at a{sub 3,1} and a{sub 3,3}, and their ratio to a{sub 3,2} both for real and imaginary values. We find abnormal symmetry of the octupole component at the level of 0.58%, compared to Monte Carlo simulations. By using the analysis of the phases of the octupole we found remarkably strong cross-correlations between the phases of the kinematic dipole and the ILC 7 octupole, in full agreement with previous results. We further test the multipole range 2 < l < 100, by investigating the ratio between the l+m = even and l+m = odd parts of power spectra. We compare the results to simulations of a Gaussian random sky, and find significant departure from the statistically isotropic and homogeneous case, for a very broad range of multipoles. We found that for the most prominent peaks of our estimator, the phases of the corresponding harmonics are coherent with phases of the octupole. We believe, our test would be very useful for detections of various types of residuals of the foreground and systematic effects at a very broad range of multipoles 2 ≤ l ≤ 1500−3000 for the forthcoming PLANCK CMB map, before any conclusions about primordial non-Gaussianity and statistical anisotropy of the CMB.
Coulson, Melissa; Healey, Michelle; Fidler, Fiona; Cumming, Geoff
2010-01-01
A statistically significant result, and a non-significant result may differ little, although significance status may tempt an interpretation of difference. Two studies are reported that compared interpretation of such results presented using null hypothesis significance testing (NHST), or confidence intervals (CIs). Authors of articles published in psychology, behavioral neuroscience, and medical journals were asked, via email, to interpret two fictitious studies that found similar results, one statistically significant, and the other non-significant. Responses from 330 authors varied greatly, but interpretation was generally poor, whether results were presented as CIs or using NHST. However, when interpreting CIs respondents who mentioned NHST were 60% likely to conclude, unjustifiably, the two results conflicted, whereas those who interpreted CIs without reference to NHST were 95% likely to conclude, justifiably, the two results were consistent. Findings were generally similar for all three disciplines. An email survey of academic psychologists confirmed that CIs elicit better interpretations if NHST is not invoked. Improved statistical inference can result from encouragement of meta-analytic thinking and use of CIs but, for full benefit, such highly desirable statistical reform requires also that researchers interpret CIs without recourse to NHST. PMID:21607077
Gershgorin, B.; Majda, A.J.
2011-02-20
A statistically exactly solvable model for passive tracers is introduced as a test model for the authors' Nonlinear Extended Kalman Filter (NEKF) as well as other filtering algorithms. The model involves a Gaussian velocity field and a passive tracer governed by the advection-diffusion equation with an imposed mean gradient. The model has direct relevance to engineering problems such as the spread of pollutants in the air or contaminants in the water as well as climate change problems concerning the transport of greenhouse gases such as carbon dioxide with strongly intermittent probability distributions consistent with the actual observations of the atmosphere. One of the attractive properties of the model is the existence of the exact statistical solution. In particular, this unique feature of the model provides an opportunity to design and test fast and efficient algorithms for real-time data assimilation based on rigorous mathematical theory for a turbulence model problem with many active spatiotemporal scales. Here, we extensively study the performance of the NEKF which uses the exact first and second order nonlinear statistics without any approximations due to linearization. The role of partial and sparse observations, the frequency of observations and the observation noise strength in recovering the true signal, its spectrum, and fat tail probability distribution are the central issues discussed here. The results of our study provide useful guidelines for filtering realistic turbulent systems with passive tracers through partial observations.
A Statistical Approach for Testing Cross-Phenotype Effects of Rare Variants
Broadaway, K. Alaine; Cutler, David J.; Duncan, Richard; Moore, Jacob L.; Ware, Erin B.; Jhun, Min A.; Bielak, Lawrence F.; Zhao, Wei; Smith, Jennifer A.; Peyser, Patricia A.; Kardia, Sharon L.R.; Ghosh, Debashis; Epstein, Michael P.
2016-01-01
Increasing empirical evidence suggests that many genetic variants influence multiple distinct phenotypes. When cross-phenotype effects exist, multivariate association methods that consider pleiotropy are often more powerful than univariate methods that model each phenotype separately. Although several statistical approaches exist for testing cross-phenotype effects for common variants, there is a lack of similar tests for gene-based analysis of rare variants. In order to fill this important gap, we introduce a statistical method for cross-phenotype analysis of rare variants using a nonparametric distance-covariance approach that compares similarity in multivariate phenotypes to similarity in rare-variant genotypes across a gene. The approach can accommodate both binary and continuous phenotypes and further can adjust for covariates. Our approach yields a closed-form test whose significance can be evaluated analytically, thereby improving computational efficiency and permitting application on a genome-wide scale. We use simulated data to demonstrate that our method, which we refer to as the Gene Association with Multiple Traits (GAMuT) test, provides increased power over competing approaches. We also illustrate our approach using exome-chip data from the Genetic Epidemiology Network of Arteriopathy. PMID:26942286
Tests of Mediation: Paradoxical Decline in Statistical Power as a Function of Mediator Collinearity.
Beasley, T Mark
2014-01-01
Increasing the correlation between the independent variable and the mediator (a coefficient) increases the effect size (ab) for mediation analysis; however, increasing a by definition increases collinearity in mediation models. As a result, the standard error of product tests increase. The variance inflation due to increases in a at some point outweighs the increase of the effect size (ab) and results in a loss of statistical power. This phenomenon also occurs with nonparametric bootstrapping approaches because the variance of the bootstrap distribution of ab approximates the variance expected from normal theory. Both variances increase dramatically when a exceeds the b coefficient, thus explaining the power decline with increases in a. Implications for statistical analysis and applied researchers are discussed. PMID:24954952
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.
Statistical analysis of aquifer-test results for nine regional aquifers in Louisiana
Martin, Angel; Early, D.A.
1987-01-01
This report, prepared as part of the Gulf Coast Regional Aquifer-System Analysis project, presents a compilation, summarization, and statistical analysis of aquifer-test results for nine regional aquifers in Louisiana. These are from youngest to oldest: The alluvial, Pleistocene, Evangeline, Jasper, Catahoula, Cockfield, Sparta, Carrizo, and Wilcox aquifers. Approximately 1,500 aquifer tests in U.S. Geological Survey files in Louisiana were examined and 1,001 were input to a computer file. Analysis of the aquifer test results and plots that describe aquifer hydraulic characteristics were made for each regional aquifer. Results indicate that, on the average, permeability (hydraulic conductivity) generally tends to decrease from the youngest aquifers to the oldest. The most permeable aquifers in Louisiana are the alluvial and Pleistocene aquifers; whereas, the least permeable are the Carrizo and Wilcox aquifers. (Author 's abstract)
ERIC Educational Resources Information Center
van Krimpen-Stoop, Edith M. L. A.; Meijer, Rob R.
Person-fit research in the context of paper-and-pencil tests is reviewed, and some specific problems regarding person fit in the context of computerized adaptive testing (CAT) are discussed. Some new methods are proposed to investigate person fit in a CAT environment. These statistics are based on Statistical Process Control (SPC) theory. A…
Statistical characterization of negative control data in the Ames Salmonella/microsome test.
Hamada, C; Wada, T; Sakamoto, Y
1994-01-01
A statistical characterization of negative control data in the Ames Salmonella/microsome reverse mutation test was performed using data obtained at Takeda Analytical Research Laboratories during January 1989 to April 1990. The lot-to-lot variability of bacterial stock cultures and day-to-day variability of experiments were small for Salmonella typhimurium strains TA1535 and TA1537 and Escherichia coli WP2uvrA, but they were larger for S. typhimurium TA100. The number of revertant colonies for all test strains studied here followed Poisson distributions within the same day. The two-fold rule that is an empirical method to evaluate the Ames Salmonella/microsome test results has been widely used in Japan. This two-fold rule was evaluated statistically. The comparison-wise type I error rate was less than 0.05 for TA98, TA100, TA1535, TA1537, and WP2uvrA. Moreover, this rule is particularly conservative for TA100, for which the type I error rate was nearly 0. PMID:8187699
Rountree, Wes; Vandergrift, Nathan; Bainbridge, John; Sanchez, Ana M; Denny, Thomas N
2014-07-01
In September 2011 Duke University was awarded a contract to develop the National Institutes of Health/National Institute of Allergy and Infectious Diseases (NIH/NIAID) External Quality Assurance Program Oversight Laboratory (EQAPOL). Through EQAPOL, proficiency testing programs are administered for Interferon-γ (IFN-γ) Enzyme-linked immunosorbent spot (ELISpot), Intracellular Cytokine Staining Flow Cytometry (ICS) and Luminex-based cytokine assays. One of the charges of the EQAPOL program was to apply statistical methods to determine overall site performance. We utilized various statistical methods for each program to find the most appropriate for assessing laboratory performance using the consensus average as the target value. Accuracy ranges were calculated based on Wald-type confidence intervals, exact Poisson confidence intervals, or via simulations. Given the nature of proficiency testing data, which has repeated measures within donor/sample made across several laboratories; the use of mixed effects models with alpha adjustments for multiple comparisons was also explored. Mixed effects models were found to be the most useful method to assess laboratory performance with respect to accuracy to the consensus. Model based approaches to the proficiency testing data in EQAPOL will continue to be utilized. Mixed effects models also provided a means of performing more complex analyses that would address secondary research questions regarding within and between laboratory variability as well as longitudinal analyses. PMID:24456626
Drug-excipient compatibility testing using a high-throughput approach and statistical design.
Wyttenbach, Nicole; Birringer, Christian; Alsenz, Jochem; Kuentz, Martin
2005-01-01
The aim of our research was to develop a miniaturized high throughput drug-excipient compatibility test. Experiments were planned and evaluated using statistical experimental design. Binary mixtures of a drug, acetylsalicylic acid, or fluoxetine hydrochloride, and of excipients commonly used in solid dosage forms were prepared at a ratio of approximately 1:100 in 96-well microtiter plates. Samples were exposed to different temperature (40 degrees C/ 50 degrees C) and humidity (10%/75%) for different time (1 week/4 weeks), and chemical drug degradation was analyzed using a fast gradient high pressure liquid chromatography (HPLC). Categorical statistical design was applied to identify the effects and interactions of time, temperature, humidity, and excipient on drug degradation. Acetylsalicylic acid was least stable in the presence of magnesium stearate, dibasic calcium phosphate, or sodium starch glycolate. Fluoxetine hydrochloride exhibited a marked degradation only with lactose. Factor-interaction plots revealed that the relative humidity had the strongest effect on the drug excipient blends tested. In conclusion, the developed technique enables fast drug-excipient compatibility testing and identification of interactions. Since only 0.1 mg of drug is needed per data point, fast rational preselection of the pharmaceutical additives can be performed early in solid dosage form development.
A statistical method of testing the gamma ray emission mechanisms of blazars.
NASA Astrophysics Data System (ADS)
Chi, X.; Young, E. C. M.
1997-09-01
Models for generation of high energy gamma rays in blazars can be classified into two types of mechanisms in the jet comoving frame: relativistic electron scattering on the internal photons or magnetic field (virtual photons) (SIP) and on the external photons (SEP). These two mechanisms are known to result in a significant difference in the beaming effect. In this work, we propose a statistical test for the two types of mechanisms based on the beaming difference. The random variable is taken to be the K-corrected gamma ray to radio flux ratio and its distribution is shown to be a power-law with an index being model-dependent. The feasibility of such a test is investigated with a limited sample of data which are complied from the EGRET gamma ray survey, low resolution radio surveys and a VLBI radio survey. A correlation study indicates that the VLBI data are more suitable for the purpose than the low resolution data. Due to the limited amount of available data, the current test result is not statistically significant to discriminate the two emission mechanisms. Future generation of high energy gamma ray telescopes are needed to produce a larger sample of data of gamma ray blazars and their simultaneous observations with VLBI are called.
A Novel Statistic for Global Association Testing Based on Penalized Regression.
Austin, Erin; Shen, Xiaotong; Pan, Wei
2015-09-01
Natural genetic structures like genes may contain multiple variants that work as a group to determine a biologic outcome. The effect of rare variants, mutations occurring in less than 5% of samples, is hypothesized to be explained best as groups collectively associated with a biologic function. Therefore, it is important to develop powerful association tests to identify a true association between an outcome of interest and a group of variants, in particular a group with many rare variants. In this article we first delineate a novel penalized regression-based global test for the association between sets of variants and a disease phenotype. Next, we use Genetic Analysis Workshop 18 (GAW18) data to assess the power of the new global association test to capture a relationship between an aggregated group of variants and a simulated hypertension status. Rare variant only, common variant only, and combined variant groups are studied. The power values are compared to those obtained from eight well-regarded global tests (Score, Sum, SSU, SSUw, UminP, aSPU, aSPUw, and sequence kernel association test (SKAT)) that do not use penalized regression and a set of tests using either the SSU or score statistics and least absolute shrinkage and selection operator penalty (LASSO) logistic regression. Association testing of rare variants with our method was the top performer when there was low linkage disequilibrium (LD) between and within causal variants. This was similarly true when simultaneously testing rare and common variants in low LD scenarios. Finally, our method was able to provide meaningful variant-specific association information.
A statistical F test for the natural attenuation of contaminants in groundwater.
Pelayo, Aristeo M; Evangelista, Fe S
2003-03-01
Natural attenuation (NA) is a catchall explanation for the overall decay and slowed movement of the contaminants in the subsurface. One direct support to NA is to demonstrate that contaminant concentrations from monitoring wells located near the source are decreasing over time. The decrease is summarily expressed in terms of an apparent half-life that is determined from the line best fitting the observed log-transformed concentration data and time. This simple (time-only) decay model assumes other factors are invariant, and so is flawed when complicating factors--such as a fluctuating water table--are present. A history of the water-table fluctuation can track changes in important NA factors like recharge, groundwater flow direction and velocity, as well as other non-NA factors like volume of water in and purged from the well before a sample is collected. When the trend in the concentrations is better associated with the water table rising or falling, any conclusion about degradation rate may be premature. We develop simple regressions to predict contaminant concentration (c) by two line models: one involving time (c approximately c(t)), and another involving groundwater elevation (c approximately c(z)). We develop a third model that includes both factors (c approximately c(t, z)). Using an F-test to compare the fits to the models, we determine which model is statistically better in explaining the observed concentrations. We applied the test to sites where benzene degradation rates had previously been estimated. The F-test can be used to determine the suitability of applying non-parametric statistics, like the Mann-Kendall, to the concentration data, because the result from the F-test can indicate instability of the contaminant plume that may be masked when the water table fluctuates.
Li, Ke; Zhang, Qiuju; Wang, Kun; Chen, Peng; Wang, Huaqing
2016-01-01
A new fault diagnosis method for rotating machinery based on adaptive statistic test filter (ASTF) and Diagnostic Bayesian Network (DBN) is presented in this paper. ASTF is proposed to obtain weak fault features under background noise, ASTF is based on statistic hypothesis testing in the frequency domain to evaluate similarity between reference signal (noise signal) and original signal, and remove the component of high similarity. The optimal level of significance α is obtained using particle swarm optimization (PSO). To evaluate the performance of the ASTF, evaluation factor Ipq is also defined. In addition, a simulation experiment is designed to verify the effectiveness and robustness of ASTF. A sensitive evaluation method using principal component analysis (PCA) is proposed to evaluate the sensitiveness of symptom parameters (SPs) for condition diagnosis. By this way, the good SPs that have high sensitiveness for condition diagnosis can be selected. A three-layer DBN is developed to identify condition of rotation machinery based on the Bayesian Belief Network (BBN) theory. Condition diagnosis experiment for rolling element bearings demonstrates the effectiveness of the proposed method. PMID:26761006
Li, Ke; Zhang, Qiuju; Wang, Kun; Chen, Peng; Wang, Huaqing
2016-01-01
A new fault diagnosis method for rotating machinery based on adaptive statistic test filter (ASTF) and Diagnostic Bayesian Network (DBN) is presented in this paper. ASTF is proposed to obtain weak fault features under background noise, ASTF is based on statistic hypothesis testing in the frequency domain to evaluate similarity between reference signal (noise signal) and original signal, and remove the component of high similarity. The optimal level of significance α is obtained using particle swarm optimization (PSO). To evaluate the performance of the ASTF, evaluation factor Ipq is also defined. In addition, a simulation experiment is designed to verify the effectiveness and robustness of ASTF. A sensitive evaluation method using principal component analysis (PCA) is proposed to evaluate the sensitiveness of symptom parameters (SPs) for condition diagnosis. By this way, the good SPs that have high sensitiveness for condition diagnosis can be selected. A three-layer DBN is developed to identify condition of rotation machinery based on the Bayesian Belief Network (BBN) theory. Condition diagnosis experiment for rolling element bearings demonstrates the effectiveness of the proposed method.
Li, Ke; Zhang, Qiuju; Wang, Kun; Chen, Peng; Wang, Huaqing
2016-01-01
A new fault diagnosis method for rotating machinery based on adaptive statistic test filter (ASTF) and Diagnostic Bayesian Network (DBN) is presented in this paper. ASTF is proposed to obtain weak fault features under background noise, ASTF is based on statistic hypothesis testing in the frequency domain to evaluate similarity between reference signal (noise signal) and original signal, and remove the component of high similarity. The optimal level of significance α is obtained using particle swarm optimization (PSO). To evaluate the performance of the ASTF, evaluation factor Ipq is also defined. In addition, a simulation experiment is designed to verify the effectiveness and robustness of ASTF. A sensitive evaluation method using principal component analysis (PCA) is proposed to evaluate the sensitiveness of symptom parameters (SPs) for condition diagnosis. By this way, the good SPs that have high sensitiveness for condition diagnosis can be selected. A three-layer DBN is developed to identify condition of rotation machinery based on the Bayesian Belief Network (BBN) theory. Condition diagnosis experiment for rolling element bearings demonstrates the effectiveness of the proposed method. PMID:26761006
Statistical tests for detection of misspecified relationships by use of genome-screen data.
McPeek, M S; Sun, L
2000-03-01
Misspecified relationships can have serious consequences for linkage studies, resulting in either reduced power or false-positive evidence for linkage. If some individuals in the pedigree are untyped, then Mendelian errors may not be observed. Previous approaches to detection of misspecified relationships by use of genotype data were developed for sib and half-sib pairs. We extend the likelihood calculations of Göring and Ott and Boehnke and Cox to more-general relative pairs, for which identity-by-descent (IBD) status is no longer a Markov chain, and we propose a likelihood-ratio test. We also extend the identity-by-state (IBS)-based test of Ehm and Wagner to nonsib relative pairs. The likelihood-ratio test has high power, but its drawbacks include the need to construct and apply a separate Markov chain for each possible alternative relationship and the need for simulation to assess significance. The IBS-based test is simpler but has lower power. We propose two new test statistics-conditional expected IBD (EIBD) and adjusted IBS (AIBS)-designed to retain the simplicity of IBS while increasing power by taking into account chance sharing. In simulations, the power of EIBD is generally close to that of the likelihood-ratio test. The power of AIBS is higher than that of IBS, in all cases considered. We suggest a strategy of initial screening by use of EIBD and AIBS, followed by application of the likelihood-ratio test to only a subset of relative pairs, identified by use of EIBD and AIBS. We apply the methods to a Genetic Analysis Workshop 11 data set from the Collaborative Study on the Genetics of Alcoholism.
Debate on GMOs health risks after statistical findings in regulatory tests.
de Vendômois, Joël Spiroux; Cellier, Dominique; Vélot, Christian; Clair, Emilie; Mesnage, Robin; Séralini, Gilles-Eric
2010-01-01
We summarize the major points of international debate on health risk studies for the main commercialized edible GMOs. These GMOs are soy, maize and oilseed rape designed to contain new pesticide residues since they have been modified to be herbicide-tolerant (mostly to Roundup) or to produce mutated Bt toxins. The debated alimentary chronic risks may come from unpredictable insertional mutagenesis effects, metabolic effects, or from the new pesticide residues. The most detailed regulatory tests on the GMOs are three-month long feeding trials of laboratory rats, which are biochemically assessed. The tests are not compulsory, and are not independently conducted. The test data and the corresponding results are kept in secret by the companies. Our previous analyses of regulatory raw data at these levels, taking the representative examples of three GM maize NK 603, MON 810, and MON 863 led us to conclude that hepatorenal toxicities were possible, and that longer testing was necessary. Our study was criticized by the company developing the GMOs in question and the regulatory bodies, mainly on the divergent biological interpretations of statistically significant biochemical and physiological effects. We present the scientific reasons for the crucially different biological interpretations and also highlight the shortcomings in the experimental protocols designed by the company. The debate implies an enormous responsibility towards public health and is essential due to nonexistent traceability or epidemiological studies in the GMO-producing countries. PMID:20941377
Debate on GMOs health risks after statistical findings in regulatory tests.
de Vendômois, Joël Spiroux; Cellier, Dominique; Vélot, Christian; Clair, Emilie; Mesnage, Robin; Séralini, Gilles-Eric
2010-10-05
We summarize the major points of international debate on health risk studies for the main commercialized edible GMOs. These GMOs are soy, maize and oilseed rape designed to contain new pesticide residues since they have been modified to be herbicide-tolerant (mostly to Roundup) or to produce mutated Bt toxins. The debated alimentary chronic risks may come from unpredictable insertional mutagenesis effects, metabolic effects, or from the new pesticide residues. The most detailed regulatory tests on the GMOs are three-month long feeding trials of laboratory rats, which are biochemically assessed. The tests are not compulsory, and are not independently conducted. The test data and the corresponding results are kept in secret by the companies. Our previous analyses of regulatory raw data at these levels, taking the representative examples of three GM maize NK 603, MON 810, and MON 863 led us to conclude that hepatorenal toxicities were possible, and that longer testing was necessary. Our study was criticized by the company developing the GMOs in question and the regulatory bodies, mainly on the divergent biological interpretations of statistically significant biochemical and physiological effects. We present the scientific reasons for the crucially different biological interpretations and also highlight the shortcomings in the experimental protocols designed by the company. The debate implies an enormous responsibility towards public health and is essential due to nonexistent traceability or epidemiological studies in the GMO-producing countries.
Debate on GMOs Health Risks after Statistical Findings in Regulatory Tests
de Vendômois, Joël Spiroux; Cellier, Dominique; Vélot, Christian; Clair, Emilie; Mesnage, Robin; Séralini, Gilles-Eric
2010-01-01
We summarize the major points of international debate on health risk studies for the main commercialized edible GMOs. These GMOs are soy, maize and oilseed rape designed to contain new pesticide residues since they have been modified to be herbicide-tolerant (mostly to Roundup) or to produce mutated Bt toxins. The debated alimentary chronic risks may come from unpredictable insertional mutagenesis effects, metabolic effects, or from the new pesticide residues. The most detailed regulatory tests on the GMOs are three-month long feeding trials of laboratory rats, which are biochemically assessed. The tests are not compulsory, and are not independently conducted. The test data and the corresponding results are kept in secret by the companies. Our previous analyses of regulatory raw data at these levels, taking the representative examples of three GM maize NK 603, MON 810, and MON 863 led us to conclude that hepatorenal toxicities were possible, and that longer testing was necessary. Our study was criticized by the company developing the GMOs in question and the regulatory bodies, mainly on the divergent biological interpretations of statistically significant biochemical and physiological effects. We present the scientific reasons for the crucially different biological interpretations and also highlight the shortcomings in the experimental protocols designed by the company. The debate implies an enormous responsibility towards public health and is essential due to nonexistent traceability or epidemiological studies in the GMO-producing countries. PMID:20941377
Parker, Albert E; Hamilton, Martin A; Tomasino, Stephen F
2014-01-01
A performance standard for a disinfectant test method can be evaluated by quantifying the (Type I) pass-error rate for ineffective products and the (Type II) fail-error rate for highly effective products. This paper shows how to calculate these error rates for test methods where the log reduction in a microbial population is used as a measure of antimicrobial efficacy. The calculations can be used to assess performance standards that may require multiple tests of multiple microbes at multiple laboratories. Notably, the error rates account for among-laboratory variance of the log reductions estimated from a multilaboratory data set and the correlation among tests of different microbes conducted in the same laboratory. Performance standards that require that a disinfectant product pass all tests or multiple tests on average, are considered. The proposed statistical methodology is flexible and allows for a different acceptable outcome for each microbe tested, since, for example, variability may be different for different microbes. The approach can also be applied to semiquantitative methods for which product efficacy is reported as the number of positive carriers out of a treated set and the density of the microbes on control carriers is quantified, thereby allowing a log reduction to be calculated. Therefore, using the approach described in this paper, the error rates can also be calculated for semiquantitative method performance standards specified solely in terms of the maximum allowable number of positive carriers per test. The calculations are demonstrated in a case study of the current performance standard for the semiquantitative AOAC Use-Dilution Methods for Pseudomonas aeruginosa (964.02) and Staphylococcus aureus (955.15), which allow up to one positive carrier out of a set of 60 inoculated and treated carriers in each test. A simulation study was also conducted to verify the validity of the model's assumptions and accuracy. Our approach, easily implemented
Improved tests reveal that the accelarating moment release hypothesis is statistically insignificant
Hardebeck, J.L.; Felzer, K.R.; Michael, A.J.
2008-01-01
We test the hypothesis that accelerating moment release (AMR) is a precursor to large earthquakes, using data from California, Nevada, and Sumatra. Spurious cases of AMR can arise from data fitting because the time period, area, and sometimes magnitude range analyzed before each main shock are often optimized to produce the strongest AMR signal. Optimizing the search criteria can identify apparent AMR even if no robust signal exists. For both 1950-2006 California-Nevada M ??? 6.5 earthquakes and the 2004 M9.3 Sumatra earthquake, we can find two contradictory patterns in the pre-main shock earthquakes by data fitting: AMR and decelerating moment release. We compare the apparent AMR found in the real data to the apparent AMR found in four types of synthetic catalogs with no inherent AMR. When spatiotemporal clustering is included in the simulations, similar AMR signals are found by data fitting in both the real and synthetic data sets even though the synthetic data sets contain no real AMR. These tests demonstrate that apparent AMR may arise from a combination of data fitting and normal foreshock and aftershock activity. In principle, data-fitting artifacts could be avoided if the free parameters were determined from scaling relationships between the duration and spatial extent of the AMR pattern and the magnitude of the earthquake that follows it. However, we demonstrate that previously proposed scaling relationships are unstable, statistical artifacts caused by the use of a minimum magnitude for the earthquake catalog that scales with the main shock magnitude. Some recent AMR studies have used spatial regions based on hypothetical stress loading patterns, rather than circles, to select the data. We show that previous tests were biased and that unbiased tests do not find this change to the method to be an improvement. The use of declustered catalogs has also been proposed to eliminate the effect of clustering but we demonstrate that this does not increase the
A new efficient statistical test for detecting variability in the gene expression data.
Mathur, Sunil; Dolo, Samuel
2008-08-01
DNA microarray technology allows researchers to monitor the expressions of thousands of genes under different conditions. The detection of differential gene expression under two different conditions is very important in microarray studies. Microarray experiments are multi-step procedures and each step is a potential source of variance. This makes the measurement of variability difficult because approach based on gene-by-gene estimation of variance will have few degrees of freedom. It is highly possible that the assumption of equal variance for all the expression levels may not hold. Also, the assumption of normality of gene expressions may not hold. Thus it is essential to have a statistical procedure which is not based on the normality assumption and also it can detect genes with differential variance efficiently. The detection of differential gene expression variance will allow us to identify experimental variables that affect different biological processes and accuracy of DNA microarray measurements.In this article, a new nonparametric test for scale is developed based on the arctangent of the ratio of two expression levels. Most of the tests available in literature require the assumption of normal distribution, which makes them inapplicable in many situations, and it is also hard to verify the suitability of the normal distribution assumption for the given data set. The proposed test does not require the assumption of the distribution for the underlying population and hence makes it more practical and widely applicable. The asymptotic relative efficiency is calculated under different distributions, which show that the proposed test is very powerful when the assumption of normality breaks down. Monte Carlo simulation studies are performed to compare the power of the proposed test with some of the existing procedures. It is found that the proposed test is more powerful than commonly used tests under almost all the distributions considered in the study. A
ERIC Educational Resources Information Center
Zheng, Yinggan; Gierl, Mark J.; Cui, Ying
2010-01-01
This study combined the kernel smoothing procedure and a nonparametric differential item functioning statistic--Cochran's Z--to statistically test the difference between the kernel-smoothed item response functions for reference and focal groups. Simulation studies were conducted to investigate the Type I error and power of the proposed…
A statistical design for testing transgenerational genomic imprinting in natural human populations.
Li, Yao; Guo, Yunqian; Wang, Jianxin; Hou, Wei; Chang, Myron N; Liao, Duanping; Wu, Rongling
2011-02-25
Genomic imprinting is a phenomenon in which the same allele is expressed differently, depending on its parental origin. Such a phenomenon, also called the parent-of-origin effect, has been recognized to play a pivotal role in embryological development and pathogenesis in many species. Here we propose a statistical design for detecting imprinted loci that control quantitative traits based on a random set of three-generation families from a natural population in humans. This design provides a pathway for characterizing the effects of imprinted genes on a complex trait or disease at different generations and testing transgenerational changes of imprinted effects. The design is integrated with population and cytogenetic principles of gene segregation and transmission from a previous generation to next. The implementation of the EM algorithm within the design framework leads to the estimation of genetic parameters that define imprinted effects. A simulation study is used to investigate the statistical properties of the model and validate its utilization. This new design, coupled with increasingly used genome-wide association studies, should have an immediate implication for studying the genetic architecture of complex traits in humans.
Tropospheric delay statistics measured by two site test interferometers at Goldstone, California
NASA Astrophysics Data System (ADS)
Morabito, David D.; D'Addario, Larry R.; Acosta, Roberto J.; Nessel, James A.
2013-12-01
Site test interferometers (STIs) have been deployed at two locations within the NASA Deep Space Network tracking complex in Goldstone, California. An STI measures the difference of atmospheric delay fluctuations over a distance comparable to the separations of microwave antennas that could be combined as phased arrays for communication and navigation. The purpose of the Goldstone STIs is to assess the suitability of Goldstone as an uplink array site and to statistically characterize atmosphere-induced phase delay fluctuations for application to future arrays. Each instrument consists of two ~1 m diameter antennas and associated electronics separated by ~200 m. The antennas continuously observe signals emitted by geostationary satellites and produce measurements of the phase difference between the received signals. The two locations at Goldstone are separated by 12.5 km and differ in elevation by 119 m. We find that their delay fluctuations are statistically similar but do not appear as shifted versions of each other, suggesting that the length scale for evolution of the turbulence pattern is shorter than the separation between instruments. We also find that the fluctuations are slightly weaker at the higher altitude site.
Jha, Sumit Kumar; Pullum, Laura L; Ramanathan, Arvind
2016-01-01
Embedded intelligent systems ranging from tiny im- plantable biomedical devices to large swarms of autonomous un- manned aerial systems are becoming pervasive in our daily lives. While we depend on the flawless functioning of such intelligent systems, and often take their behavioral correctness and safety for granted, it is notoriously difficult to generate test cases that expose subtle errors in the implementations of machine learning algorithms. Hence, the validation of intelligent systems is usually achieved by studying their behavior on representative data sets, using methods such as cross-validation and bootstrapping.In this paper, we present a new testing methodology for studying the correctness of intelligent systems. Our approach uses symbolic decision procedures coupled with statistical hypothesis testing to. We also use our algorithm to analyze the robustness of a human detection algorithm built using the OpenCV open-source computer vision library. We show that the human detection implementation can fail to detect humans in perturbed video frames even when the perturbations are so small that the corresponding frames look identical to the naked eye.
Empirical-Statistics Analysis for Zero-Failure GaAs MMICs Life Testing Data
NASA Astrophysics Data System (ADS)
Huang, Zheng-Liang; Yu, Fa-Xin; Zhang, Shu-Ting; Luo, Hao; Wang, Ping-Hui; Zheng, Yao
GaAs MMICs (Monolithic Microwave Integrated Circuits) reliability is a critical part of the overall reliability of the thermal solution in semiconductor devices. With MMICs reliability improved, GaAs MMICs failure rates will reach levels which are impractical to measure with conventional methods in the near future. This letter proposes a methodology to predict the GaAs MMICs reliability by combining empirical and statistical methods based on zero-failure GaAs MMICs life testing data. Besides, we investigate the effect of accelerated factors on MMICs degradation and make a comparison between the Weibull and lognormal distributions. The method has been used in the reliability evaluation of GaAs MMICs successfully.
Experimental Test of Heisenberg's Measurement Uncertainty Relation Based on Statistical Distances.
Ma, Wenchao; Ma, Zhihao; Wang, Hengyan; Chen, Zhihua; Liu, Ying; Kong, Fei; Li, Zhaokai; Peng, Xinhua; Shi, Mingjun; Shi, Fazhan; Fei, Shao-Ming; Du, Jiangfeng
2016-04-22
Incompatible observables can be approximated by compatible observables in joint measurement or measured sequentially, with constrained accuracy as implied by Heisenberg's original formulation of the uncertainty principle. Recently, Busch, Lahti, and Werner proposed inaccuracy trade-off relations based on statistical distances between probability distributions of measurement outcomes [P. Busch et al., Phys. Rev. Lett. 111, 160405 (2013); P. Busch et al., Phys. Rev. A 89, 012129 (2014)]. Here we reformulate their theoretical framework, derive an improved relation for qubit measurement, and perform an experimental test on a spin system. The relation reveals that the worst-case inaccuracy is tightly bounded from below by the incompatibility of target observables, and is verified by the experiment employing joint measurement in which two compatible observables designed to approximate two incompatible observables on one qubit are measured simultaneously.
Experimental Test of Heisenberg's Measurement Uncertainty Relation Based on Statistical Distances.
Ma, Wenchao; Ma, Zhihao; Wang, Hengyan; Chen, Zhihua; Liu, Ying; Kong, Fei; Li, Zhaokai; Peng, Xinhua; Shi, Mingjun; Shi, Fazhan; Fei, Shao-Ming; Du, Jiangfeng
2016-04-22
Incompatible observables can be approximated by compatible observables in joint measurement or measured sequentially, with constrained accuracy as implied by Heisenberg's original formulation of the uncertainty principle. Recently, Busch, Lahti, and Werner proposed inaccuracy trade-off relations based on statistical distances between probability distributions of measurement outcomes [P. Busch et al., Phys. Rev. Lett. 111, 160405 (2013); P. Busch et al., Phys. Rev. A 89, 012129 (2014)]. Here we reformulate their theoretical framework, derive an improved relation for qubit measurement, and perform an experimental test on a spin system. The relation reveals that the worst-case inaccuracy is tightly bounded from below by the incompatibility of target observables, and is verified by the experiment employing joint measurement in which two compatible observables designed to approximate two incompatible observables on one qubit are measured simultaneously. PMID:27152779
Experimental Test of Heisenberg's Measurement Uncertainty Relation Based on Statistical Distances
NASA Astrophysics Data System (ADS)
Ma, Wenchao; Ma, Zhihao; Wang, Hengyan; Chen, Zhihua; Liu, Ying; Kong, Fei; Li, Zhaokai; Peng, Xinhua; Shi, Mingjun; Shi, Fazhan; Fei, Shao-Ming; Du, Jiangfeng
2016-04-01
Incompatible observables can be approximated by compatible observables in joint measurement or measured sequentially, with constrained accuracy as implied by Heisenberg's original formulation of the uncertainty principle. Recently, Busch, Lahti, and Werner proposed inaccuracy trade-off relations based on statistical distances between probability distributions of measurement outcomes [P. Busch et al., Phys. Rev. Lett. 111, 160405 (2013); P. Busch et al., Phys. Rev. A 89, 012129 (2014)]. Here we reformulate their theoretical framework, derive an improved relation for qubit measurement, and perform an experimental test on a spin system. The relation reveals that the worst-case inaccuracy is tightly bounded from below by the incompatibility of target observables, and is verified by the experiment employing joint measurement in which two compatible observables designed to approximate two incompatible observables on one qubit are measured simultaneously.
ERIC Educational Resources Information Center
Luh, Wei-Ming; Guo, Jiin-Huarng
2005-01-01
To deal with nonnormal and heterogeneous data for the one-way fixed effect analysis of variance model, the authors adopted a trimmed means method in conjunction with Hall's invertible transformation into a heteroscedastic test statistic (Alexander-Govern test or Welch test). The results of simulation experiments showed that the proposed technique…
NASA Astrophysics Data System (ADS)
Guo, Bingjie; Bitner-Gregersen, Elzbieta Maria; Sun, Hui; Block Helmers, Jens
2013-04-01
Earlier investigations have indicated that proper prediction of nonlinear loads and responses due to nonlinear waves is important for ship safety in extreme seas. However, the nonlinear loads and responses in extreme seas have not been sufficiently investigated yet, particularly when rogue waves are considered. A question remains whether the existing linear codes can predict nonlinear loads and responses with a satisfactory accuracy and how large the deviations from linear predictions are. To indicate it response statistics have been studied based on the model tests carried out with a LNG tanker in the towing tank of the Technical University of Berlin (TUB), and compared with the statistics derived from numerical simulations using the DNV code WASIM. It is a potential code for wave-ship interaction based on 3D Panel method, which can perform both linear and nonlinear simulation. The numerical simulations with WASIM and the model tests in extreme and rogue waves have been performed. The analysis of ship motions (heave and pitch) and bending moments, in both regular and irregular waves, is performed. The results from the linear and nonlinear simulations are compared with experimental data to indicate the impact of wave non-linearity on loads and response calculations when the code based on the Rankine Panel Method is used. The study shows that nonlinearities may have significant effect on extreme motions and bending moment generated by strongly nonlinear waves. The effect of water depth on ship responses is also demonstrated using numerical simulations. Uncertainties related to the results are discussed, giving particular attention to sampling variability.
Combining test statistics and models in bootstrapped model rejection: it is a balancing act
2014-01-01
Background Model rejections lie at the heart of systems biology, since they provide conclusive statements: that the corresponding mechanistic assumptions do not serve as valid explanations for the experimental data. Rejections are usually done using e.g. the chi-square test (χ2) or the Durbin-Watson test (DW). Analytical formulas for the corresponding distributions rely on assumptions that typically are not fulfilled. This problem is partly alleviated by the usage of bootstrapping, a computationally heavy approach to calculate an empirical distribution. Bootstrapping also allows for a natural extension to estimation of joint distributions, but this feature has so far been little exploited. Results We herein show that simplistic combinations of bootstrapped tests, like the max or min of the individual p-values, give inconsistent, i.e. overly conservative or liberal, results. A new two-dimensional (2D) approach based on parametric bootstrapping, on the other hand, is found both consistent and with a higher power than the individual tests, when tested on static and dynamic examples where the truth is known. In the same examples, the most superior test is a 2D χ2vsχ2, where the second χ2-value comes from an additional help model, and its ability to describe bootstraps from the tested model. This superiority is lost if the help model is too simple, or too flexible. If a useful help model is found, the most powerful approach is the bootstrapped log-likelihood ratio (LHR). We show that this is because the LHR is one-dimensional, because the second dimension comes at a cost, and because LHR has retained most of the crucial information in the 2D distribution. These approaches statistically resolve a previously published rejection example for the first time. Conclusions We have shown how to, and how not to, combine tests in a bootstrap setting, when the combination is advantageous, and when it is advantageous to include a second model. These results also provide a deeper
ERIC Educational Resources Information Center
Tabor, Josh
2010-01-01
On the 2009 AP[c] Statistics Exam, students were asked to create a statistic to measure skewness in a distribution. This paper explores several of the most popular student responses and evaluates which statistic performs best when sampling from various skewed populations. (Contains 8 figures, 3 tables, and 4 footnotes.)
DWPF Sample Vial Insert Study-Statistical Analysis of DWPF Mock-Up Test Data
Harris, S.P.
1997-09-18
This report is prepared as part of Technical/QA Task Plan WSRC-RP-97-351 which was issued in response to Technical Task Request HLW/DWPF/TTR-970132 submitted by DWPF. Presented in this report is a statistical analysis of DWPF Mock-up test data for evaluation of two new analytical methods which use insert samples from the existing HydragardTM sampler. The first is a new hydrofluoric acid based method called the Cold Chemical Method (Cold Chem) and the second is a modified fusion method.Either new DWPF analytical method could result in a two to three fold improvement in sample analysis time.Both new methods use the existing HydragardTM sampler to collect a smaller insert sample from the process sampling system. The insert testing methodology applies to the DWPF Slurry Mix Evaporator (SME) and the Melter Feed Tank (MFT) samples.The insert sample is named after the initial trials which placed the container inside the sample (peanut) vials. Samples in small 3 ml containers (Inserts) are analyzed by either the cold chemical method or a modified fusion method. The current analytical method uses a HydragardTM sample station to obtain nearly full 15 ml peanut vials. The samples are prepared by a multi-step process for Inductively Coupled Plasma (ICP) analysis by drying, vitrification, grinding and finally dissolution by either mixed acid or fusion. In contrast, the insert sample is placed directly in the dissolution vessel, thus eliminating the drying, vitrification and grinding operations for the Cold chem method. Although the modified fusion still requires drying and calcine conversion, the process is rapid due to the decreased sample size and that no vitrification step is required.A slurry feed simulant material was acquired from the TNX pilot facility from the test run designated as PX-7.The Mock-up test data were gathered on the basis of a statistical design presented in SRT-SCS-97004 (Rev. 0). Simulant PX-7 samples were taken in the DWPF Analytical Cell Mock
McAlinden, Colm; Khadka, Jyoti; Pesudovs, Konrad
2011-07-01
The ever-expanding choice of ocular metrology and imaging equipment has driven research into the validity of their measurements. Consequently, studies of the agreement between two instruments or clinical tests have proliferated in the ophthalmic literature. It is important that researchers apply the appropriate statistical tests in agreement studies. Correlation coefficients are hazardous and should be avoided. The 'limits of agreement' method originally proposed by Altman and Bland in 1983 is the statistical procedure of choice. Its step-by-step use and practical considerations in relation to optometry and ophthalmology are detailed in addition to sample size considerations and statistical approaches to precision (repeatability or reproducibility) estimates.
Statistical methods for the analysis of a screening test for chronic beryllium disease
Frome, E.L.; Neubert, R.L.; Smith, M.H.; Littlefield, L.G.; Colyer, S.P.
1994-10-01
The lymphocyte proliferation test (LPT) is a noninvasive screening procedure used to identify persons who may have chronic beryllium disease. A practical problem in the analysis of LPT well counts is the occurrence of outlying data values (approximately 7% of the time). A log-linear regression model is used to describe the expected well counts for each set of test conditions. The variance of the well counts is proportional to the square of the expected counts, and two resistant regression methods are used to estimate the parameters of interest. The first approach uses least absolute values (LAV) on the log of the well counts to estimate beryllium stimulation indices (SIs) and the coefficient of variation. The second approach uses a resistant regression version of maximum quasi-likelihood estimation. A major advantage of the resistant regression methods is that it is not necessary to identify and delete outliers. These two new methods for the statistical analysis of the LPT data and the outlier rejection method that is currently being used are applied to 173 LPT assays. The authors strongly recommend the LAV method for routine analysis of the LPT.
Test Statistics for the Identification of Assembly Neurons in Parallel Spike Trains
Picado Muiño, David; Borgelt, Christian
2015-01-01
In recent years numerous improvements have been made in multiple-electrode recordings (i.e., parallel spike-train recordings) and spike sorting to the extent that nowadays it is possible to monitor the activity of up to hundreds of neurons simultaneously. Due to these improvements it is now potentially possible to identify assembly activity (roughly understood as significant synchronous spiking of a group of neurons) from these recordings, which—if it can be demonstrated reliably—would significantly improve our understanding of neural activity and neural coding. However, several methodological problems remain when trying to do so and, among them, a principal one is the combinatorial explosion that one faces when considering all potential neuronal assemblies, since in principle every subset of the recorded neurons constitutes a candidate set for an assembly. We present several statistical tests to identify assembly neurons (i.e., neurons that participate in a neuronal assembly) from parallel spike trains with the aim of reducing the set of neurons to a relevant subset of them and this way ease the task of identifying neuronal assemblies in further analyses. These tests are an improvement of those introduced in the work by Berger et al. (2010) based on additional features like spike weight or pairwise overlap and on alternative ways to identify spike coincidences (e.g., by avoiding time binning, which tends to lose information). PMID:25866503
NASA Astrophysics Data System (ADS)
Peñarrubia, Jorge; Koposov, Sergey E.; Walker, Matthew G.
2012-11-01
We introduce the Minimum Entropy Method, a simple statistical technique for constraining the Milky Way gravitational potential and simultaneously testing different gravity theories directly from 6D phase-space surveys and without adopting dynamical models. We demonstrate that orbital energy distributions that are separable (i.e., independent of position) have an associated entropy that increases under wrong assumptions about the gravitational potential and/or gravity theory. Of known objects, "cold" tidal streams from low-mass progenitors follow orbital distributions that most nearly satisfy the condition of separability. Although the orbits of tidally stripped stars are perturbed by the progenitor's self-gravity, systematic variations of the energy distribution can be quantified in terms of the cross-entropy of individual tails, giving further sensitivity to theoretical biases in the host potential. The feasibility of using the Minimum Entropy Method to test a wide range of gravity theories is illustrated by evolving restricted N-body models in a Newtonian potential and examining the changes in entropy introduced by Dirac, MONDian, and f(R) gravity modifications.
Statistical testing of the full-range leadership theory in nursing.
Kanste, Outi; Kääriäinen, Maria; Kyngäs, Helvi
2009-12-01
The aim of this study is to test statistically the structure of the full-range leadership theory in nursing. The data were gathered by postal questionnaires from nurses and nurse leaders working in healthcare organizations in Finland. A follow-up study was performed 1 year later. The sample consisted of 601 nurses and nurse leaders, and the follow-up study had 78 respondents. Theory was tested through structural equation modelling, standard regression analysis and two-way anova. Rewarding transformational leadership seems to promote and passive laissez-faire leadership to reduce willingness to exert extra effort, perceptions of leader effectiveness and satisfaction with the leader. Active management-by-exception seems to reduce willingness to exert extra effort and perception of leader effectiveness. Rewarding transformational leadership remained as a strong explanatory factor of all outcome variables measured 1 year later. The data supported the main structure of the full-range leadership theory, lending support to the universal nature of the theory.
A Tool Preference Choice Method for RNA Secondary Structure Prediction by SVM with Statistical Tests
Hor, Chiou-Yi; Yang, Chang-Biau; Chang, Chia-Hung; Tseng, Chiou-Ting; Chen, Hung-Hsin
2013-01-01
The Prediction of RNA secondary structures has drawn much attention from both biologists and computer scientists. Many useful tools have been developed for this purpose. These tools have their individual strengths and weaknesses. As a result, based on support vector machines (SVM), we propose a tool choice method which integrates three prediction tools: pknotsRG, RNAStructure, and NUPACK. Our method first extracts features from the target RNA sequence, and adopts two information-theoretic feature selection methods for feature ranking. We propose a method to combine feature selection and classifier fusion in an incremental manner. Our test data set contains 720 RNA sequences, where 225 pseudoknotted RNA sequences are obtained from PseudoBase, and 495 nested RNA sequences are obtained from RNA SSTRAND. The method serves as a preprocessing way in analyzing RNA sequences before the RNA secondary structure prediction tools are employed. In addition, the performance of various configurations is subject to statistical tests to examine their significance. The best base-pair accuracy achieved is 75.5%, which is obtained by the proposed incremental method, and is significantly higher than 68.8%, which is associated with the best predictor, pknotsRG. PMID:23641141
Létourneau, Daniel McNiven, Andrea; Keller, Harald; Wang, An; Amin, Md Nurul; Pearce, Jim; Norrlinger, Bernhard; Jaffray, David A.
2014-12-15
Purpose: High-quality radiation therapy using highly conformal dose distributions and image-guided techniques requires optimum machine delivery performance. In this work, a monitoring system for multileaf collimator (MLC) performance, integrating semiautomated MLC quality control (QC) tests and statistical process control tools, was developed. The MLC performance monitoring system was used for almost a year on two commercially available MLC models. Control charts were used to establish MLC performance and assess test frequency required to achieve a given level of performance. MLC-related interlocks and servicing events were recorded during the monitoring period and were investigated as indicators of MLC performance variations. Methods: The QC test developed as part of the MLC performance monitoring system uses 2D megavoltage images (acquired using an electronic portal imaging device) of 23 fields to determine the location of the leaves with respect to the radiation isocenter. The precision of the MLC performance monitoring QC test and the MLC itself was assessed by detecting the MLC leaf positions on 127 megavoltage images of a static field. After initial calibration, the MLC performance monitoring QC test was performed 3–4 times/week over a period of 10–11 months to monitor positional accuracy of individual leaves for two different MLC models. Analysis of test results was performed using individuals control charts per leaf with control limits computed based on the measurements as well as two sets of specifications of ±0.5 and ±1 mm. Out-of-specification and out-of-control leaves were automatically flagged by the monitoring system and reviewed monthly by physicists. MLC-related interlocks reported by the linear accelerator and servicing events were recorded to help identify potential causes of nonrandom MLC leaf positioning variations. Results: The precision of the MLC performance monitoring QC test and the MLC itself was within ±0.22 mm for most MLC leaves
A statistical test on the reliability of the non-coevality of stars in binary systems
NASA Astrophysics Data System (ADS)
Valle, G.; Dell'Omodarme, M.; Prada Moroni, P. G.; Degl'Innocenti, S.
2016-03-01
Aims: We develop a statistical test on the expected difference in age estimates of two coeval stars in detached double-lined eclipsing binary systems that are only caused by observational uncertainties. We focus on stars in the mass range [0.8; 1.6] M⊙, with an initial metallicity [Fe/H] from -0.55 to 0.55 dex, and on stars in the main-sequence phase. Methods: The ages were obtained by means of the SCEPtER technique, a maximum-likelihood procedure relying on a pre-computed grid of stellar models. The observational constraints used in the recovery procedure are stellar mass, radius, effective temperature, and metallicity [Fe/H]. To check the effect of the uncertainties affecting observations on the (non-)coevality assessment, the chosen observational constraints were subjected to a Gaussian perturbation before applying the SCEPtER code. We defined the statistic W computed as the ratio of the absolute difference of estimated ages for the two stars over the age of the older one. We determined the critical values of this statistics above which coevality can be rejected in dependence on the mass of the two stars, on the initial metallicity [Fe/H], and on the evolutionary stage of the primary star. Results: The median expected difference in the reconstructed age between the coeval stars of a binary system - caused alone by the observational uncertainties - shows a strong dependence on the evolutionary stage. This ranges from about 20% for an evolved primary star to about 75% for a near ZAMS primary. The median difference also shows an increase with the mass of the primary star from 20% for 0.8 M⊙ stars to about 50% for 1.6 M⊙ stars. The reliability of these results was checked by repeating the process with a grid of stellar models computed by a different evolutionary code; the median difference in the critical values was only 0.01. We show that the W test is much more sensible to age differences in the binary system components than the alternative approach of
Quantile estimation to derive optimized test thresholds for random field statistics.
Hinrichs, H; Scholz, M; Noesselt, T; Heinze, H J
2005-08-01
We present a numerical method to estimate the true threshold values in random fields needed to determine the significance of apparent signals observed in noisy images. To accomplish this, a quantile estimation algorithm is applied to derive the threshold with a predefined confidence interval from a large number of simulated random fields. Also, a computationally efficient method for generating a random field simulation is presented using resampling techniques. Applying these techniques, thresholds have been determined for a large variety of parameter settings (smoothness, voxel size, brain shape, type of statistics). By means of interpolation techniques, thresholds for additional arbitrary settings can be quickly derived without the need to run individual simulations. Compared to the parametric approach of Worsley et al. (1996) (Worsley, K.J., Marrett, S., Neelin P., Vandal, A.C., Friston, K.J., Evans, A.C., 1996. A unified statistical approach for determining significant signals in images of cerebral activation. Hum. Brain Mapp. 4, 58-73) and Friston et al. (1991) (Friston, K.J., Frith, C.D., Liddle, P.F., Frackowiak, R.S. 1991. Comparing functional (PET) images: the assessment of significant change. J. Cereb. Blood Flow Metab. 11(4), 690-699), and to the Bonferroni approach, these optimized thresholds lead to higher levels of significance (i.e., lower p values) with a specific amount of activation especially with fields of moderate smoothness (i.e., with a relative full width half maximum between 2 and 6). Alternatively, the threshold for a specified level of significance can be lowered. This improved statistical sensitivity is illustrated by the analysis of an actual event related functional magnetic resonance data set, and its limitations are tested by determining the false positive rate with experimental MR noise data. The grid of estimated threshold values as well as the interpolation algorithm to derive thresholds for arbitrary parameter settings are made
Semenov, Alexander V; Elsas, Jan Dirk; Glandorf, Debora C M; Schilthuizen, Menno; Boer, Willem F
2013-08-01
To fulfill existing guidelines, applicants that aim to place their genetically modified (GM) insect-resistant crop plants on the market are required to provide data from field experiments that address the potential impacts of the GM plants on nontarget organisms (NTO's). Such data may be based on varied experimental designs. The recent EFSA guidance document for environmental risk assessment (2010) does not provide clear and structured suggestions that address the statistics of field trials on effects on NTO's. This review examines existing practices in GM plant field testing such as the way of randomization, replication, and pseudoreplication. Emphasis is placed on the importance of design features used for the field trials in which effects on NTO's are assessed. The importance of statistical power and the positive and negative aspects of various statistical models are discussed. Equivalence and difference testing are compared, and the importance of checking the distribution of experimental data is stressed to decide on the selection of the proper statistical model. While for continuous data (e.g., pH and temperature) classical statistical approaches - for example, analysis of variance (ANOVA) - are appropriate, for discontinuous data (counts) only generalized linear models (GLM) are shown to be efficient. There is no golden rule as to which statistical test is the most appropriate for any experimental situation. In particular, in experiments in which block designs are used and covariates play a role GLMs should be used. Generic advice is offered that will help in both the setting up of field testing and the interpretation and data analysis of the data obtained in this testing. The combination of decision trees and a checklist for field trials, which are provided, will help in the interpretation of the statistical analyses of field trials and to assess whether such analyses were correctly applied. We offer generic advice to risk assessors and applicants that will
Hamilton, Martin A; Hamilton, Gordon Cord; Goeres, Darla M; Parker, Albert E
2013-01-01
This paper presents statistical techniques suitable for analyzing a collaborative study (multilaboratory study or ring trial) of a laboratory disinfectant product performance test (DPPT) method. Emphasis is on the assessment of the repeatability, reproducibility, resemblance, and responsiveness of the DPPT method. The suggested statistical techniques are easily modified for application to a single laboratory study. The presentation includes descriptions of the plots and tables that should be constructed during initial examination of the data, including a discussion of outliers and QA checks. The statistical recommendations deal with evaluations of prevailing types of DPPTs, including both quantitative and semiquantitative tests. The presentation emphasizes tests in which the disinfectant treatment is applied to surface-associated microbes and the outcome is a viable cell count; however, the statistical guidelines are appropriate for suspension tests and other test systems. The recommendations also are suitable for disinfectant tests using any microbe (vegetative bacteria, virus, spores, etc.) or any disinfectant treatment. The descriptions of the statistical techniques include either examples of calculations based on published data or citations to published calculations. Computer code is provided in an appendix.
KURETZKI, Carlos Henrique; CAMPOS, Antônio Carlos Ligocki; MALAFAIA, Osvaldo; SOARES, Sandramara Scandelari Kusano de Paula; TENÓRIO, Sérgio Bernardo; TIMI, Jorge Rufino Ribas
2016-01-01
Background: The use of information technology is often applied in healthcare. With regard to scientific research, the SINPE(c) - Integrated Electronic Protocols was created as a tool to support researchers, offering clinical data standardization. By the time, SINPE(c) lacked statistical tests obtained by automatic analysis. Aim: Add to SINPE(c) features for automatic realization of the main statistical methods used in medicine . Methods: The study was divided into four topics: check the interest of users towards the implementation of the tests; search the frequency of their use in health care; carry out the implementation; and validate the results with researchers and their protocols. It was applied in a group of users of this software in their thesis in the strict sensu master and doctorate degrees in one postgraduate program in surgery. To assess the reliability of the statistics was compared the data obtained both automatically by SINPE(c) as manually held by a professional in statistics with experience with this type of study. Results: There was concern for the use of automatic statistical tests, with good acceptance. The chi-square, Mann-Whitney, Fisher and t-Student were considered as tests frequently used by participants in medical studies. These methods have been implemented and thereafter approved as expected. Conclusion: The incorporation of the automatic SINPE(c) Statistical Analysis was shown to be reliable and equal to the manually done, validating its use as a research tool for medical research. PMID:27120732
ERIC Educational Resources Information Center
Hambleton, Ronald K.; And Others
Four item bias methods were studied. The methods compared include the Mantel-Haenszel statistic, the plot method, the route mean squared difference method, and the total area method; the latter two methods are based on item response theory. The test consisted of item responses of 451 male and 486 female ninth graders to 75 test items on the 1985…
Chlorine-36 data at Yucca Mountain: Statistical tests of conceptual models for unsaturated-zone flow
Campbell, K.; Wolfsberg, A.; Fabryka-Martin, J.; Sweetkind, D.
2003-01-01
An extensive set of chlorine-36 (36Cl) data has been collected in the Exploratory Studies Facility (ESF), an 8-km-long tunnel at Yucca Mountain, Nevada, for the purpose of developing and testing conceptual models of flow and transport in the unsaturated zone (UZ) at this site. At several locations, the measured values of 36Cl/Cl ratios for salts leached from rock samples are high enough to provide strong evidence that at least a small component of bomb-pulse 36Cl, fallout from atmospheric testing of nuclear devices in the 1950s and 1960s, was measured, implying that some fraction of the water traveled from the ground surface through 200-300 m of unsaturated rock to the level of the ESF during the last 50 years. These data are analyzed here using a formal statistical approach based on log-linear models to evaluate alternative conceptual models for the distribution of such fast flow paths. The most significant determinant of the presence of bomb-pulse 36Cl in a sample from the welded Topopah Spring unit (TSw) is the structural setting from which the sample was collected. Our analysis generally supports the conceptual model that a fault that cuts through the nonwelded Paintbrush tuff unit (PTn) that overlies the TSw is required in order for bomb-pulse 36Cl to be transmitted to the sample depth in less than 50 years. Away from PTn-cutting faults, the ages of water samples at the ESF appear to be a strong function of the thickness of the nonwelded tuff between the ground surface and the ESF, due to slow matrix flow in that unit. ?? 2002 Elsevier Science B.V. All rights reserved.
Ramus, Claire; Hovasse, Agnès; Marcellin, Marlène; Hesse, Anne-Marie; Mouton-Barbosa, Emmanuelle; Bouyssié, David; Vaca, Sebastian; Carapito, Christine; Chaoui, Karima; Bruley, Christophe; Garin, Jérôme; Cianférani, Sarah; Ferro, Myriam; Dorssaeler, Alain Van; Burlet-Schiltz, Odile; Schaeffer, Christine; Couté, Yohann; Gonzalez de Peredo, Anne
2016-03-01
This data article describes a controlled, spiked proteomic dataset for which the "ground truth" of variant proteins is known. It is based on the LC-MS analysis of samples composed of a fixed background of yeast lysate and different spiked amounts of the UPS1 mixture of 48 recombinant proteins. It can be used to objectively evaluate bioinformatic pipelines for label-free quantitative analysis, and their ability to detect variant proteins with good sensitivity and low false discovery rate in large-scale proteomic studies. More specifically, it can be useful for tuning software tools parameters, but also testing new algorithms for label-free quantitative analysis, or for evaluation of downstream statistical methods. The raw MS files can be downloaded from ProteomeXchange with identifier PXD001819. Starting from some raw files of this dataset, we also provide here some processed data obtained through various bioinformatics tools (including MaxQuant, Skyline, MFPaQ, IRMa-hEIDI and Scaffold) in different workflows, to exemplify the use of such data in the context of software benchmarking, as discussed in details in the accompanying manuscript [1]. The experimental design used here for data processing takes advantage of the different spike levels introduced in the samples composing the dataset, and processed data are merged in a single file to facilitate the evaluation and illustration of software tools results for the detection of variant proteins with different absolute expression levels and fold change values.
The Effects of Pre-Lecture Quizzes on Test Anxiety and Performance in a Statistics Course
ERIC Educational Resources Information Center
Brown, Michael J.; Tallon, Jennifer
2015-01-01
The purpose of our study was to examine the effects of pre-lecture quizzes in a statistics course. Students (N = 70) from 2 sections of an introductory statistics course served as participants in this study. One section completed pre-lecture quizzes whereas the other section did not. Completing pre-lecture quizzes was associated with improved exam…
The T(ea) Test: Scripted Stories Increase Statistical Method Selection Skills
ERIC Educational Resources Information Center
Hackathorn, Jana; Ashdown, Brien
2015-01-01
To teach statistics, teachers must attempt to overcome pedagogical obstacles, such as dread, anxiety, and boredom. There are many options available to teachers that facilitate a pedagogically conducive environment in the classroom. The current study examined the effectiveness of incorporating scripted stories and humor into statistical method…
ERIC Educational Resources Information Center
Jones, Andrew T.
2011-01-01
Practitioners often depend on item analysis to select items for exam forms and have a variety of options available to them. These include the point-biserial correlation, the agreement statistic, the B index, and the phi coefficient. Although research has demonstrated that these statistics can be useful for item selection, no research as of yet has…
ERIC Educational Resources Information Center
Fidalgo, Angel M.; Alavi, Seyed Mohammad; Amirian, Seyed Mohammad Reza
2014-01-01
This study examines three controversial aspects in differential item functioning (DIF) detection by logistic regression (LR) models: first, the relative effectiveness of different analytical strategies for detecting DIF; second, the suitability of the Wald statistic for determining the statistical significance of the parameters of interest; and…
Brown, Geoffrey W.; Sandstrom, Mary M.; Preston, Daniel N.; Pollard, Colin J.; Warner, Kirstin F.; Sorensen, Daniel N.; Remmers, Daniel L.; Phillips, Jason J.; Shelley, Timothy J.; Reyes, Jose A.; et al
2014-11-17
In this study, the Integrated Data Collection Analysis (IDCA) program has conducted a proficiency test for small-scale safety and thermal (SSST) testing of homemade explosives (HMEs). Described here are statistical analyses of the results from this test for impact, friction, electrostatic discharge, and differential scanning calorimetry analysis of the RDX Class 5 Type II standard. The material was tested as a well-characterized standard several times during the proficiency test to assess differences among participants and the range of results that may arise for well-behaved explosive materials.
NASA Astrophysics Data System (ADS)
Shiraishi, Maresuke; Hikage, Chiaki; Namba, Ryo; Namikawa, Toshiya; Hazumi, Masashi
2016-08-01
The B -mode polarization in the cosmic microwave background (CMB) anisotropies at large angular scales provides compelling evidence for the primordial gravitational waves (GWs). It is often stated that a discovery of the GWs establishes the quantum fluctuation of vacuum during the cosmic inflation. Since the GWs could also be generated by source fields, however, we need to check if a sizable signal exists due to such source fields before reaching a firm conclusion when the B mode is discovered. Source fields of particular types can generate non-Gaussianity (NG) in the GWs. Testing statistics of the B mode is a powerful way of detecting such NG. As a concrete example, we show a model in which gauge field sources chiral GWs via a pseudoscalar coupling and forecast the detection significance at the future CMB satellite LiteBIRD. Effects of residual foregrounds and lensing B mode are both taken into account. We find the B -mode bispectrum "BBB" is in particular sensitive to the source-field NG, which is detectable at LiteBIRD with a >3 σ significance. Therefore the search for the BBB will be indispensable toward unambiguously establishing quantum fluctuation of vacuum when the B mode is discovered. We also introduced the Minkowski functional to detect the NGs. While we find that the Minkowski functional is less efficient than the harmonic-space bispectrum estimator, it still serves as a useful cross-check. Finally, we also discuss the possibility of extracting clean information on parity violation of GWs and new types of parity-violating observables induced by lensing.
An objective statistical test for eccentricity forcing of Oligo-Miocene climate
NASA Astrophysics Data System (ADS)
Proistosescu, C.; Huybers, P.; Maloof, A. C.
2008-12-01
We seek a maximally objective test for the presence of orbital features in Oligocene and Miocene δ18O records from marine sediments. Changes in Earth's orbital eccentricity are thought to be an important control on the long term variability of climate during the Oligocene and Miocene Epochs. However, such an important control from eccentricity is surprising because eccentricity has relatively little influence on Earth's annual average insolation budget. Nevertheless, if significant eccentricity variability is present, it would provide important insight into the operation of the climate system at long timescales. Here we use previously published data, but using a chronology which is initially independent of orbital assumptions, to test for the presence of eccentricity period variability in the Oligocene/Miocene sediment records. In contrast to the sawtooth climate record of the Pleistocene, the Oligocene and Miocene climate record appears smooth and symmetric and does not reset itself every hundred thousand years. This smooth variation, as well as the time interval spanning many eccentricity periods makes Oligocene and Miocene paleorecords very suitable for evaluating the importance of eccentricity forcing. First, we construct time scales depending only upon the ages of geomagnetic reversals with intervening ages linearly interpolated with depth. Such a single age-depth relationship is, however, too uncertain to assess whether orbital features are present. Thus, we construct a second depth-derived age-model by averaging ages across multiple sediment cores which have, at least partly, independent accumulation rate histories. But ages are still too uncertain to permit unambiguous detection of orbital variability. Thus we employ limited tuning assumptions and measure the degree by orbital period variability increases using spectral power estimates. By tuning we know that we are biasing the record toward showing orbital variations, but we account for this bias in our
Using the {delta}{sub 3} statistic to test for missed levels in neutron resonance data
Mulhall, Declan
2009-03-31
The {delta}{sub 3}(L) statistic is studied as a possible tool to detect missing levels in the neutron resonance data of odd-A nuclei. A {delta}{sub 3}(L) analysis of neutron resonance data is compared with the results of a maximum likelihood method applied to the level spacing distribution. The {delta}{sub 3}(L) statistic compares favorably with the level spacing distribution as a tool to gauge the completeness of the data.
ERIC Educational Resources Information Center
Oshima, T. C.; Raju, Nambury S.; Nanda, Alice O.
2006-01-01
A new item parameter replication method is proposed for assessing the statistical significance of the noncompensatory differential item functioning (NCDIF) index associated with the differential functioning of items and tests framework. In this new method, a cutoff score for each item is determined by obtaining a (1-alpha ) percentile rank score…
NASA Astrophysics Data System (ADS)
Berti, Matteo; Corsini, Alessandro; Franceschini, Silvia; Iannacone, Jean Pascal
2013-04-01
The application of space borne synthetic aperture radar interferometry has progressed, over the last two decades, from the pioneer use of single interferograms for analyzing changes on the earth's surface to the development of advanced multi-interferogram techniques to analyze any sort of natural phenomena which involves movements of the ground. The success of multi-interferograms techniques in the analysis of natural hazards such as landslides and subsidence is widely documented in the scientific literature and demonstrated by the consensus among the end-users. Despite the great potential of this technique, radar interpretation of slope movements is generally based on the sole analysis of average displacement velocities, while the information embraced in multi interferogram time series is often overlooked if not completely neglected. The underuse of PS time series is probably due to the detrimental effect of residual atmospheric errors, which make the PS time series characterized by erratic, irregular fluctuations often difficult to interpret, and also to the difficulty of performing a visual, supervised analysis of the time series for a large dataset. In this work is we present a procedure for automatic classification of PS time series based on a series of statistical characterization tests. The procedure allows to classify the time series into six distinctive target trends (0=uncorrelated; 1=linear; 2=quadratic; 3=bilinear; 4=discontinuous without constant velocity; 5=discontinuous with change in velocity) and retrieve for each trend a series of descriptive parameters which can be efficiently used to characterize the temporal changes of ground motion. The classification algorithms were developed and tested using an ENVISAT datasets available in the frame of EPRS-E project (Extraordinary Plan of Environmental Remote Sensing) of the Italian Ministry of Environment (track "Modena", Northern Apennines). This dataset was generated using standard processing, then the
Semenov, Alexander V; Elsas, Jan Dirk; Glandorf, Debora C M; Schilthuizen, Menno; Boer, Willem F
2013-08-01
To fulfill existing guidelines, applicants that aim to place their genetically modified (GM) insect-resistant crop plants on the market are required to provide data from field experiments that address the potential impacts of the GM plants on nontarget organisms (NTO's). Such data may be based on varied experimental designs. The recent EFSA guidance document for environmental risk assessment (2010) does not provide clear and structured suggestions that address the statistics of field trials on effects on NTO's. This review examines existing practices in GM plant field testing such as the way of randomization, replication, and pseudoreplication. Emphasis is placed on the importance of design features used for the field trials in which effects on NTO's are assessed. The importance of statistical power and the positive and negative aspects of various statistical models are discussed. Equivalence and difference testing are compared, and the importance of checking the distribution of experimental data is stressed to decide on the selection of the proper statistical model. While for continuous data (e.g., pH and temperature) classical statistical approaches - for example, analysis of variance (ANOVA) - are appropriate, for discontinuous data (counts) only generalized linear models (GLM) are shown to be efficient. There is no golden rule as to which statistical test is the most appropriate for any experimental situation. In particular, in experiments in which block designs are used and covariates play a role GLMs should be used. Generic advice is offered that will help in both the setting up of field testing and the interpretation and data analysis of the data obtained in this testing. The combination of decision trees and a checklist for field trials, which are provided, will help in the interpretation of the statistical analyses of field trials and to assess whether such analyses were correctly applied. We offer generic advice to risk assessors and applicants that will
Semenov, Alexander V; Elsas, Jan Dirk; Glandorf, Debora C M; Schilthuizen, Menno; Boer, Willem F
2013-01-01
Abstract To fulfill existing guidelines, applicants that aim to place their genetically modified (GM) insect-resistant crop plants on the market are required to provide data from field experiments that address the potential impacts of the GM plants on nontarget organisms (NTO's). Such data may be based on varied experimental designs. The recent EFSA guidance document for environmental risk assessment (2010) does not provide clear and structured suggestions that address the statistics of field trials on effects on NTO's. This review examines existing practices in GM plant field testing such as the way of randomization, replication, and pseudoreplication. Emphasis is placed on the importance of design features used for the field trials in which effects on NTO's are assessed. The importance of statistical power and the positive and negative aspects of various statistical models are discussed. Equivalence and difference testing are compared, and the importance of checking the distribution of experimental data is stressed to decide on the selection of the proper statistical model. While for continuous data (e.g., pH and temperature) classical statistical approaches – for example, analysis of variance (ANOVA) – are appropriate, for discontinuous data (counts) only generalized linear models (GLM) are shown to be efficient. There is no golden rule as to which statistical test is the most appropriate for any experimental situation. In particular, in experiments in which block designs are used and covariates play a role GLMs should be used. Generic advice is offered that will help in both the setting up of field testing and the interpretation and data analysis of the data obtained in this testing. The combination of decision trees and a checklist for field trials, which are provided, will help in the interpretation of the statistical analyses of field trials and to assess whether such analyses were correctly applied. We offer generic advice to risk assessors and
ERIC Educational Resources Information Center
Adams, David R.
1977-01-01
Discusses the application of the Kolmogorov-Smirnov two-sample tests, as an alternative to the Chi-square test, for survey research problems in business education and includes a computer program written for the convenience of researchers. The two-sample test is recommended for differentiating independent distributions. (MF)
Festing, Michael F. W.
2014-01-01
The safety of chemicals, drugs, novel foods and genetically modified crops is often tested using repeat-dose sub-acute toxicity tests in rats or mice. It is important to avoid misinterpretations of the results as these tests are used to help determine safe exposure levels in humans. Treated and control groups are compared for a range of haematological, biochemical and other biomarkers which may indicate tissue damage or other adverse effects. However, the statistical analysis and presentation of such data poses problems due to the large number of statistical tests which are involved. Often, it is not clear whether a “statistically significant” effect is real or a false positive (type I error) due to sampling variation. The author's conclusions appear to be reached somewhat subjectively by the pattern of statistical significances, discounting those which they judge to be type I errors and ignoring any biomarker where the p-value is greater than p = 0.05. However, by using standardised effect sizes (SESs) a range of graphical methods and an over-all assessment of the mean absolute response can be made. The approach is an extension, not a replacement of existing methods. It is intended to assist toxicologists and regulators in the interpretation of the results. Here, the SES analysis has been applied to data from nine published sub-acute toxicity tests in order to compare the findings with those of the author's. Line plots, box plots and bar plots show the pattern of response. Dose-response relationships are easily seen. A “bootstrap” test compares the mean absolute differences across dose groups. In four out of seven papers where the no observed adverse effect level (NOAEL) was estimated by the authors, it was set too high according to the bootstrap test, suggesting that possible toxicity is under-estimated. PMID:25426843
NASA Astrophysics Data System (ADS)
Hilborn, Robert C.
1997-04-01
The connection between the spin of particles and the permutation symmetry ("statistics") of multiparticle states lies at the heart of much of atomic, molecular, condensed matter, and nuclear physics. The spin-statistics theorem of relativistic quantum field theory seems to provide a theoretical basis for this connection. There are, however, loopholes (O. W. Greenberg, Phys. Rev. D 43, 4111 (1991).) that allow for a field theory of identical particles whose statistics interpolate smoothly between that of bosons and fermions. Thus, it is up to experiment to reveal how closely nature follows the usual spin- statistics connection. After reviewing experiments that provide stringent limits on possible violations of the spin-statistics connection for electrons, I shall describe recent analogous experiments for spin-0 particles (R. C. Hilborn and C. L. Yuca, Phys. Rev. Lett. 76, 2844 (1996).) using diode laser spectroscopy of the A-band of molecular oxygen near 760 nm. These experiments show that the probability of finding two ^16O nuclei (spin-0 particles) in an antisymmetric state is less than 1ppm. I shall also discuss proposals to test the spin-statistics connection for photons.
Residuals and the Residual-Based Statistic for Testing Goodness of Fit of Structural Equation Models
ERIC Educational Resources Information Center
Foldnes, Njal; Foss, Tron; Olsson, Ulf Henning
2012-01-01
The residuals obtained from fitting a structural equation model are crucial ingredients in obtaining chi-square goodness-of-fit statistics for the model. The authors present a didactic discussion of the residuals, obtaining a geometrical interpretation by recognizing the residuals as the result of oblique projections. This sheds light on the…
The Adequacy of Different Robust Statistical Tests in Comparing Two Independent Groups
ERIC Educational Resources Information Center
Pero-Cebollero, Maribel; Guardia-Olmos, Joan
2013-01-01
In the current study, we evaluated various robust statistical methods for comparing two independent groups. Two scenarios for simulation were generated: one of equality and another of population mean differences. In each of the scenarios, 33 experimental conditions were used as a function of sample size, standard deviation and asymmetry. For each…
Basic Mathematics Test Predicts Statistics Achievement and Overall First Year Academic Success
ERIC Educational Resources Information Center
Fonteyne, Lot; De Fruyt, Filip; Dewulf, Nele; Duyck, Wouter; Erauw, Kris; Goeminne, Katy; Lammertyn, Jan; Marchant, Thierry; Moerkerke, Beatrijs; Oosterlinck, Tom; Rosseel, Yves
2015-01-01
In the psychology and educational science programs at Ghent University, only 36.1% of the new incoming students in 2011 and 2012 passed all exams. Despite availability of information, many students underestimate the scientific character of social science programs. Statistics courses are a major obstacle in this matter. Not all enrolling students…
A Statistical Analysis of Infrequent Events on Multiple-Choice Tests that Indicate Probable Cheating
ERIC Educational Resources Information Center
Sundermann, Michael J.
2008-01-01
A statistical analysis of multiple-choice answers is performed to identify anomalies that can be used as evidence of student cheating. The ratio of exact errors in common (EEIC: two students put the same wrong answer for a question) to differences (D: two students get different answers) was found to be a good indicator of cheating under a wide…
Accuracy of Estimates and Statistical Power for Testing Meditation in Latent Growth Curve Modeling
ERIC Educational Resources Information Center
Cheong, JeeWon
2011-01-01
The latent growth curve modeling (LGCM) approach has been increasingly utilized to investigate longitudinal mediation. However, little is known about the accuracy of the estimates and statistical power when mediation is evaluated in the LGCM framework. A simulation study was conducted to address these issues under various conditions including…
Carvajal-Rodríguez, Antonio; de Uña-Alvarez, Jacobo; Rolán-Alvarez, Emilio
2009-01-01
Background The detection of true significant cases under multiple testing is becoming a fundamental issue when analyzing high-dimensional biological data. Unfortunately, known multitest adjustments reduce their statistical power as the number of tests increase. We propose a new multitest adjustment, based on a sequential goodness of fit metatest (SGoF), which increases its statistical power with the number of tests. The method is compared with Bonferroni and FDR-based alternatives by simulating a multitest context via two different kinds of tests: 1) one-sample t-test, and 2) homogeneity G-test. Results It is shown that SGoF behaves especially well with small sample sizes when 1) the alternative hypothesis is weakly to moderately deviated from the null model, 2) there are widespread effects through the family of tests, and 3) the number of tests is large. Conclusion Therefore, SGoF should become an important tool for multitest adjustment when working with high-dimensional biological data. PMID:19586526
Statistical Detection of Multiple-Choice Test Answer Copying: State of the Art.
ERIC Educational Resources Information Center
Frary, Robert B.
Practical and effective methods for detecting copying of multiple-choice test responses have been available for many years. These methods have been used routinely by large admissions and licensing testing programs. However, these methods are seldom applied in the areas of standardized or classroom testing in schools or colleges, and knowledge…
ERIC Educational Resources Information Center
Alexandrowicz, Rainer W.
2011-01-01
The linear logistic test model (LLTM) is a valuable and approved tool in educational research, as it allows for modelling cognitive components involved in a cognitive task. It allows for a rigorous assessment of fit by means of a Likelihood Ratio Test (LRT). This approach is genuine to the Rasch family of models, yet it suffers from the unsolved…
Method for nondestructive testing using multiple-energy CT and statistical pattern classification
NASA Astrophysics Data System (ADS)
Homem, Murillo R. P.; Mascarenhas, Nelson D. A.; Cruvinel, Paulo E.
1999-10-01
This paper reports on how multiple energy techniques in X and gamma-ray CT scanning are able to provide good results with the use of Statistical Pattern Classification theory. We obtained a set of four images with different energies (40, 60, 85 and 662 keV) containing aluminum, phosphorus, calcium, water and plexiglass, with a minitomograph scanner for soil science. We analyzed those images through both a supervised classifier based on the maximum-likelihood criterion under the multivariate Gaussian model and a supervised contextual classifier based on the ICM (iterated conditional modes) algorithm using an a priori Potts-Strauss model. A comparison between them was performed through the statistical kappa coefficient. A feature selection procedure using the Jeffries- Matusita (J-M) Distance was also performed. Both the classification and the feature selection procedures were found to be in agreement with the predicted discrimination given by the separation of the linear attenuation coefficient curves for different materials.
Consistency in statistical moments as a test for bubble cloud clustering.
Weber, Thomas C; Lyons, Anthony P; Bradley, David L
2011-11-01
Frequency dependent measurements of attenuation and/or sound speed through clouds of gas bubbles in liquids are often inverted to find the bubble size distribution and the void fraction of gas. The inversions are often done using an effective medium theory as a forward model under the assumption that the bubble positions are Poisson distributed (i.e., statistically independent). Under circumstances in which single scattering does not adequately describe the pressure field, the assumption of independence in position can yield large errors when clustering is present, leading to errors in the inverted bubble size distribution. It is difficult, however, to determine the existence of clustering in bubble clouds without the use of specialized acoustic or optical imaging equipment. A method is described here in which the existence of bubble clustering can be identified by examining the consistency between the first two statistical moments of multiple frequency acoustic measurements.
Consistency in statistical moments as a test for bubble cloud clustering.
Weber, Thomas C; Lyons, Anthony P; Bradley, David L
2011-11-01
Frequency dependent measurements of attenuation and/or sound speed through clouds of gas bubbles in liquids are often inverted to find the bubble size distribution and the void fraction of gas. The inversions are often done using an effective medium theory as a forward model under the assumption that the bubble positions are Poisson distributed (i.e., statistically independent). Under circumstances in which single scattering does not adequately describe the pressure field, the assumption of independence in position can yield large errors when clustering is present, leading to errors in the inverted bubble size distribution. It is difficult, however, to determine the existence of clustering in bubble clouds without the use of specialized acoustic or optical imaging equipment. A method is described here in which the existence of bubble clustering can be identified by examining the consistency between the first two statistical moments of multiple frequency acoustic measurements. PMID:22088013
Weber, Benjamin; Lee, Sau L; Delvadia, Renishkumar; Lionberger, Robert; Li, Bing V; Tsong, Yi; Hochhaus, Guenther
2015-03-01
Equivalence testing of aerodynamic particle size distribution (APSD) through multi-stage cascade impactors (CIs) is important for establishing bioequivalence of orally inhaled drug products. Recent work demonstrated that the median of the modified chi-square ratio statistic (MmCSRS) is a promising metric for APSD equivalence testing of test (T) and reference (R) products as it can be applied to a reduced number of CI sites that are more relevant for lung deposition. This metric is also less sensitive to the increased variability often observed for low-deposition sites. A method to establish critical values for the MmCSRS is described here. This method considers the variability of the R product by employing a reference variance scaling approach that allows definition of critical values as a function of the observed variability of the R product. A stepwise CI equivalence test is proposed that integrates the MmCSRS as a method for comparing the relative shapes of CI profiles and incorporates statistical tests for assessing equivalence of single actuation content and impactor sized mass. This stepwise CI equivalence test was applied to 55 published CI profile scenarios, which were classified as equivalent or inequivalent by members of the Product Quality Research Institute working group (PQRI WG). The results of the stepwise CI equivalence test using a 25% difference in MmCSRS as an acceptance criterion provided the best matching with those of the PQRI WG as decisions of both methods agreed in 75% of the 55 CI profile scenarios.
Statistical considerations of the random selection process in a drug testing program
Burtis, C.A.; Owings, J.H.; Leete, R.S. Jr.
1987-01-01
In a prospective drug testing program, individuals whose job classifications have been defined as sensitive are placed in a selection pool. On a periodic basis, individuals are chosen from this pool for drug testing. Random selection is a fair and impartial approach. A random selection process generates a Poisson distribution of probabilities that can be used to predict how many times an individual will be selected during a specific time interval. This information can be used to model the selection part of a drug testing program to determine whether specific conditions of testing are met. For example, the probability of being selected a given number of times during the testing period can be minimized or maximized by varying the frequency of the sampling process. Consequently, the Poisson distribution and the mathematics governing it can be used to structure a drug testing program to meet the needs and dictates of any given situation.
NASA Technical Reports Server (NTRS)
Hughes, William O.; McNelis, Anne M.
2010-01-01
The Earth Observing System (EOS) Terra spacecraft was launched on an Atlas IIAS launch vehicle on its mission to observe planet Earth in late 1999. Prior to launch, the new design of the spacecraft's pyroshock separation system was characterized by a series of 13 separation ground tests. The analysis methods used to evaluate this unusually large amount of shock data will be discussed in this paper, with particular emphasis on population distributions and finding statistically significant families of data, leading to an overall shock separation interface level. The wealth of ground test data also allowed a derivation of a Mission Assurance level for the flight. All of the flight shock measurements were below the EOS Terra Mission Assurance level thus contributing to the overall success of the EOS Terra mission. The effectiveness of the statistical methodology for characterizing the shock interface level and for developing a flight Mission Assurance level from a large sample size of shock data is demonstrated in this paper.
ERIC Educational Resources Information Center
Woodruff, David; Wu, Yi-Fang
2012-01-01
The purpose of this paper is to illustrate alpha's robustness and usefulness, using actual and simulated educational test data. The sampling properties of alpha are compared with the sampling properties of several other reliability coefficients: Guttman's lambda[subscript 2], lambda[subscript 4], and lambda[subscript 6]; test-retest reliability;…
ERIC Educational Resources Information Center
Deacon, S. Helene; Leung, Dilys
2013-01-01
This study tested the diverging predictions of recent theories of children's learning of spelling regularities. We asked younger (Grades 1 and 2) and older (Grades 3 and 4) elementary school-aged children to choose the correct endings for words that varied in their morphological structure. We tested the impacts of semantic frequency by…
Hybrid Statistical Testing for Nuclear Material Accounting Data and/or Process Monitoring Data
Ticknor, Lawrence O.; Hamada, Michael Scott; Sprinkle, James K.; Burr, Thomas Lee
2015-04-14
The two tests employed in the hybrid testing scheme are Page’s cumulative sums for all streams within a Balance Period (maximum of the maximums and average of the maximums) and Crosier’s multivariate cumulative sum applied to incremental cumulative sums across Balance Periods. The role of residuals for both kinds of data is discussed.
Multilevel Factor Analysis by Model Segregation: New Applications for Robust Test Statistics
ERIC Educational Resources Information Center
Schweig, Jonathan
2014-01-01
Measures of classroom environments have become central to policy efforts that assess school and teacher quality. This has sparked a wide interest in using multilevel factor analysis to test measurement hypotheses about classroom-level variables. One approach partitions the total covariance matrix and tests models separately on the…
Statistical tests for analysing directed movement of self-organising animal groups.
Merrifield, A; Myerscough, Mary R; Weber, N
2006-09-01
We discuss some theory concerning directional data and introduce a suite of statistical tools that researchers interested in the directional movement of animal groups can use to analyse results from their models. We illustrate these tools by analysing the results of a model of groups moving under the duress of certain informed indistinguishable individuals, that arises in the context of honeybee (Apis mellifera) swarming behaviour. We modify an existing model of collective motion, based on inter-individual social interactions, allowing knowledgeable individuals to guide group members to the goal by travelling through the group in a direct line aligned with the goal direction.
Divine, George; Norton, H James; Hunt, Ronald; Dienemann, Jacqueline
2013-09-01
When a study uses an ordinal outcome measure with unknown differences in the anchors and a small range such as 4 or 7, use of the Wilcoxon rank sum test or the Wilcoxon signed rank test may be most appropriate. However, because nonparametric methods are at best indirect functions of standard measures of location such as means or medians, the choice of the most appropriate summary measure can be difficult. The issues underlying use of these tests are discussed. The Wilcoxon-Mann-Whitney odds directly reflects the quantity that the rank sum procedure actually tests, and thus it can be a superior summary measure. Unlike the means and medians, its value will have a one-to-one correspondence with the Wilcoxon rank sum test result. The companion article appearing in this issue of Anesthesia & Analgesia ("Aromatherapy as Treatment for Postoperative Nausea: A Randomized Trial") illustrates these issues and provides an example of a situation for which the medians imply no difference between 2 groups, even though the groups are, in fact, quite different. The trial cited also provides an example of a single sample that has a median of zero, yet there is a substantial shift for much of the nonzero data, and the Wilcoxon signed rank test is quite significant. These examples highlight the potential discordance between medians and Wilcoxon test results. Along with the issues surrounding the choice of a summary measure, there are considerations for the computation of sample size and power, confidence intervals, and multiple comparison adjustment. In addition, despite the increased robustness of the Wilcoxon procedures relative to parametric tests, some circumstances in which the Wilcoxon tests may perform poorly are noted, along with alternative versions of the procedures that correct for such limitations. PMID:23456667
On statistical properties of test functions in nonparametric methods for periodogram analysis.
NASA Astrophysics Data System (ADS)
Andronov, I. L.; Chinarova, L. L.
Periodogram analysis methods in the modifications by Lafler and Kinman (1965), Burke et al. (1970), Deeming (1970), Renson (1978), and Dworetsky (1983) are compared. Mean values, variances, skewness, and excesses of test functions are determined for some numerical models, and correlations between them are discussed. Analytical estimates are obtained for the mathematical expectation of test functions in different methods and for the variance of the test function by Lafler and Kinman (1965). An algorithm of choosing the optimum period is discussed, the technique proposed is used to determine the orbital period of the eclipsing binary star HBV 426 = V1147 Cyg; the period is found to be 1.097383d.
Denton, Debra L; Diamond, Jerry; Zheng, Lei
2011-05-01
The U.S. Environmental Protection Agency (U.S. EPA) and state agencies implement the Clean Water Act, in part, by evaluating the toxicity of effluent and surface water samples. A common goal for both regulatory authorities and permittees is confidence in an individual test result (e.g., no-observed-effect concentration [NOEC], pass/fail, 25% effective concentration [EC25]), which is used to make regulatory decisions, such as reasonable potential determinations, permit compliance, and watershed assessments. This paper discusses an additional statistical approach (test of significant toxicity [TST]), based on bioequivalence hypothesis testing, or, more appropriately, test of noninferiority, which examines whether there is a nontoxic effect at a single concentration of concern compared with a control. Unlike the traditional hypothesis testing approach in whole effluent toxicity (WET) testing, TST is designed to incorporate explicitly both α and β error rates at levels of toxicity that are unacceptable and acceptable, given routine laboratory test performance for a given test method. Regulatory management decisions are used to identify unacceptable toxicity levels for acute and chronic tests, and the null hypothesis is constructed such that test power is associated with the ability to declare correctly a truly nontoxic sample as acceptable. This approach provides a positive incentive to generate high-quality WET data to make informed decisions regarding regulatory decisions. This paper illustrates how α and β error rates were established for specific test method designs and tests the TST approach using both simulation analyses and actual WET data. In general, those WET test endpoints having higher routine (e.g., 50th percentile) within-test control variation, on average, have higher method-specific α values (type I error rate), to maintain a desired type II error rate. This paper delineates the technical underpinnings of this approach and demonstrates the benefits
NASA Technical Reports Server (NTRS)
Dimitri, P. S.; Wall, C. 3rd; Oas, J. G.; Rauch, S. D.
2001-01-01
Meniere's disease (MD) and migraine associated dizziness (MAD) are two disorders that can have similar symptomatologies, but differ vastly in treatment. Vestibular testing is sometimes used to help differentiate between these disorders, but the inefficiency of a human interpreter analyzing a multitude of variables independently decreases its utility. Our hypothesis was that we could objectively discriminate between patients with MD and those with MAD using select variables from the vestibular test battery. Sinusoidal harmonic acceleration test variables were reduced to three vestibulo-ocular reflex physiologic parameters: gain, time constant, and asymmetry. A combination of these parameters plus a measurement of reduced vestibular response from caloric testing allowed us to achieve a joint classification rate of 91%, independent quadratic classification algorithm. Data from posturography were not useful for this type of differentiation. Overall, our classification function can be used as an unbiased assistant to discriminate between MD and MAD and gave us insight into the pathophysiologic differences between the two disorders.
A statistical analysis of effects of test methods on spun carbon nanotube yarn
NASA Astrophysics Data System (ADS)
Veliky, Kenneth Blake
Carbon nanotube (CNT) fibers are very promising materials for many applications. Strong interactions among individual CNTs could produce a dense yarn results in exceptional properties. These properties are used in the application of high-performance reinforcement for composites. . As the reinforcement, the primary function is to provide outstanding load bearing capability. Currently literatures use a variety of measurement techniques and gauge lengths that have not been uniform for CNT yarn tests. The need for a standardized testing method for characterization is necessary in generating reproducible and comparable data for CNT yarn or fiber materials. In this work, the strength of CNT fibers was characterized using three different types of tensile test method: the film and fiber test fixtures from dynamics mechanic analysis (DMA), and --TS 600 tensile fixture. Samples that underwent the film and TS 600 tensile fixture were attached with a thick paper tabbing methodology based on ASTM standard D3379. As for the fiber fixture was performed with the test material attached directly to the fixture based on the fiber test instruction from TA Instrument. The results of the three different methods provided distinct variance in stress, strain, and modulus. A design of experiment (DoE) was established and performed on the DMA film fixture as determined from the preliminary experiment. The DoE was successful in quantifying the critical parameters' ranges that attributed to standard deviation of average stress. These parameters were then tested on 30 more samples with an improved additive manufactured tab. The results significantly decreased all mechanical testing parameters' standard deviations. Most importantly, the results prove the probability of a valid gauge break increased to more than 400%.
Downward, L.; Booth, C.H.; Lukens, W.W.; Bridges, F.
2006-07-25
A general problem when fitting EXAFS data is determining whether particular parameters are statistically significant. The F-test is an excellent way of determining relevancy in EXAFS because it only relies on the ratio of the fit residual of two possible models, and therefore the data errors approximately cancel. Although this test is widely used in crystallography (there, it is often called a 'Hamilton test') and has been properly applied to EXAFS data in the past, it is very rarely applied in EXAFS analysis. We have implemented a variation of the F-test adapted for EXAFS data analysis in the RSXAP analysis package, and demonstrate its applicability with a few examples, including determining whether a particular scattering shell is warranted, and differentiating between two possible species or two possible structures in a given shell.
ERIC Educational Resources Information Center
Glas, C. A. W.
In a previous study (1998), how to evaluate whether adaptive testing data used for online calibration sufficiently fit the item response model used by C. Glas was studied. Three approaches were suggested, based on a Lagrange multiplier (LM) statistic, a Wald statistic, and a cumulative sum (CUMSUM) statistic respectively. For all these methods,…
A Statistical Test of Walrasian Equilibrium by Means of Complex Networks Theory
NASA Astrophysics Data System (ADS)
Bargigli, Leonardo; Viaggiu, Stefano; Lionetto, Andrea
2016-09-01
We represent an exchange economy in terms of statistical ensembles for complex networks by introducing the concept of market configuration. This is defined as a sequence of nonnegative discrete random variables {w_{ij}} describing the flow of a given commodity from agent i to agent j. This sequence can be arranged in a nonnegative matrix W which we can regard as the representation of a weighted and directed network or digraph G. Our main result consists in showing that general equilibrium theory imposes highly restrictive conditions upon market configurations, which are in most cases not fulfilled by real markets. An explicit example with reference to the e-MID interbank credit market is provided.
A Statistical Test of Walrasian Equilibrium by Means of Complex Networks Theory
NASA Astrophysics Data System (ADS)
Bargigli, Leonardo; Viaggiu, Stefano; Lionetto, Andrea
2016-10-01
We represent an exchange economy in terms of statistical ensembles for complex networks by introducing the concept of market configuration. This is defined as a sequence of nonnegative discrete random variables {w_{ij}} describing the flow of a given commodity from agent i to agent j. This sequence can be arranged in a nonnegative matrix W which we can regard as the representation of a weighted and directed network or digraph G. Our main result consists in showing that general equilibrium theory imposes highly restrictive conditions upon market configurations, which are in most cases not fulfilled by real markets. An explicit example with reference to the e-MID interbank credit market is provided.
Goedhart, Paul W; van der Voet, Hilko; Baldacchino, Ferdinando; Arpaia, Salvatore
2014-01-01
Genetic modification of plants may result in unintended effects causing potentially adverse effects on the environment. A comparative safety assessment is therefore required by authorities, such as the European Food Safety Authority, in which the genetically modified plant is compared with its conventional counterpart. Part of the environmental risk assessment is a comparative field experiment in which the effect on non-target organisms is compared. Statistical analysis of such trials come in two flavors: difference testing and equivalence testing. It is important to know the statistical properties of these, for example, the power to detect environmental change of a given magnitude, before the start of an experiment. Such prospective power analysis can best be studied by means of a statistical simulation model. This paper describes a general framework for simulating data typically encountered in environmental risk assessment of genetically modified plants. The simulation model, available as Supplementary Material, can be used to generate count data having different statistical distributions possibly with excess-zeros. In addition the model employs completely randomized or randomized block experiments, can be used to simulate single or multiple trials across environments, enables genotype by environment interaction by adding random variety effects, and finally includes repeated measures in time following a constant, linear or quadratic pattern in time possibly with some form of autocorrelation. The model also allows to add a set of reference varieties to the GM plants and its comparator to assess the natural variation which can then be used to set limits of concern for equivalence testing. The different count distributions are described in some detail and some examples of how to use the simulation model to study various aspects, including a prospective power analysis, are provided. PMID:24834325
Goedhart, Paul W; van der Voet, Hilko; Baldacchino, Ferdinando; Arpaia, Salvatore
2014-04-01
Genetic modification of plants may result in unintended effects causing potentially adverse effects on the environment. A comparative safety assessment is therefore required by authorities, such as the European Food Safety Authority, in which the genetically modified plant is compared with its conventional counterpart. Part of the environmental risk assessment is a comparative field experiment in which the effect on non-target organisms is compared. Statistical analysis of such trials come in two flavors: difference testing and equivalence testing. It is important to know the statistical properties of these, for example, the power to detect environmental change of a given magnitude, before the start of an experiment. Such prospective power analysis can best be studied by means of a statistical simulation model. This paper describes a general framework for simulating data typically encountered in environmental risk assessment of genetically modified plants. The simulation model, available as Supplementary Material, can be used to generate count data having different statistical distributions possibly with excess-zeros. In addition the model employs completely randomized or randomized block experiments, can be used to simulate single or multiple trials across environments, enables genotype by environment interaction by adding random variety effects, and finally includes repeated measures in time following a constant, linear or quadratic pattern in time possibly with some form of autocorrelation. The model also allows to add a set of reference varieties to the GM plants and its comparator to assess the natural variation which can then be used to set limits of concern for equivalence testing. The different count distributions are described in some detail and some examples of how to use the simulation model to study various aspects, including a prospective power analysis, are provided.
NASA Astrophysics Data System (ADS)
Andronov, I. L.; Chinarova, L. L.
1997-12-01
Numerical comparison of methods for the periodogram analysis is carried out for modifications by Lafler and Kinman (1965), Burke et al. (1970), Deeming (1970), Renson (1978) and Dworetsky (1983). For some numerical models the values of the mean, variance, asymmetry, and excess of the test functions are determined, the correlations between them are discussed. Analytic estimates of the mathematical expectation of the test function for different methods and of the dispersion of the test function by Lafler and Kinman (1965) are obtained. The algorithm of choosing the optimum period is discussed. By using the proposed method, the orbital period of the eclipsing binary star HBV 426 = V1147 Cyg is determined, which is 1.097383d.
Garbarino, J.R.; Jones, B.E.; Stein, G.P.
1985-01-01
In an interlaboratory test, inductively coupled plasma atomic emission spectrometry (ICP-AES) was compared with flame atomic absorption spectrometry and molecular absorption spectrophotometry for the determination of 17 major and trace elements in 100 filtered natural water samples. No unacceptable biases were detected. The analysis precision of ICP-AES was found to be equal to or better than alternative methods. Known-addition recovery experiments demonstrated that the ICP-AES determinations are accurate to between plus or minus 2 and plus or minus 10 percent; four-fifths of the tests yielded average recoveries of 95-105 percent, with an average relative standard deviation of about 5 percent.
Brain morphometry measurements are required in test guidelines proposed by the USEPA to screen chemicals for developmental neurotoxicity. Because the DNT is a screening battery, the analysis of this data should be sensitive to dose-related changes in the pattern of brain growt...
ERIC Educational Resources Information Center
Godleski, Stephanie A.; Ostrov, Jamie M.
2010-01-01
The present study used both categorical and dimensional approaches to test the association between relational and physical aggression and hostile intent attributions for both relational and instrumental provocation situations using the National Institute of Child Health and Human Development longitudinal Study of Early Child Care and Youth…
ERIC Educational Resources Information Center
Twiste, Tara L.
2011-01-01
The identification of patterned responding in unmotivated test takers was investigated through the formation of a novel method. The proposed method relied on marginal proportions of answer choice options as well as the transitional proportions between responses on item pairs. A chi square analysis was used to determine the degree of significance…
On the Adaptive Control of the False Discovery Rate in Multiple Testing with Independent Statistics.
ERIC Educational Resources Information Center
Benjamini, Yoav; Hochberg, Yosef
2000-01-01
Presents an adaptive approach to multiple significance testing based on the procedure of Y. Benjamini and Y. Hochberg (1995) that first estimates the number of true null hypotheses and then uses that estimate in the Benjamini and Hochberg procedure. Uses the new procedure in examples from educational and behavioral studies and shows its control of…
Tests of Mediation: Paradoxical Decline in Statistical Power as a Function of Mediator Collinearity
ERIC Educational Resources Information Center
Beasley, T. Mark
2014-01-01
Increasing the correlation between the independent variable and the mediator ("a" coefficient) increases the effect size ("ab") for mediation analysis; however, increasing a by definition increases collinearity in mediation models. As a result, the standard error of product tests increase. The variance inflation caused by…
The Probability of Exceedance as a Nonparametric Person-Fit Statistic for Tests of Moderate Length
ERIC Educational Resources Information Center
Tendeiro, Jorge N.; Meijer, Rob R.
2013-01-01
To classify an item score pattern as not fitting a nonparametric item response theory (NIRT) model, the probability of exceedance (PE) of an observed response vector x can be determined as the sum of the probabilities of all response vectors that are, at most, as likely as x, conditional on the test's total score. Vector x is to be considered…
Statistical Indexes for Monitoring Item Behavior under Computer Adaptive Testing Environment.
ERIC Educational Resources Information Center
Zhu, Renbang; Yu, Feng; Liu, Su
A computerized adaptive test (CAT) administration usually requires a large supply of items with accurately estimated psychometric properties, such as item response theory (IRT) parameter estimates, to ensure the precision of examinee ability estimation. However, an estimated IRT model of a given item in any given pool does not always correctly…
V/V_max_ statistics and neo-classic cosmological tests.
NASA Astrophysics Data System (ADS)
van Waerbeke, L.; Mathez, G.; Mellier, Y.; Bonnet, H.; Lachieze-Rey, M.
1996-12-01
A new cosmological test is derived, based on the distribution of individual V/V_max_ in a complete redshift-limited sample of distant objects. The fundamental assumption is that, in any range of absolute luminosity, individual V/V_max_ are required to be uniformly spread over the [0,1] range. Under the assumption of Pure Luminosity Evolution, this gives rise to a natural partition of the sample into high luminosity, redshift-limited and low luminosity magnitude-limited quasars. The behavior of V/V_max_ versus evolution and cosmology differs substantially in the two subsamples. This condition of uniformity is probed in any absolute magnitude bin, allowing a likelihood function to be computed from the Kolmogorov-Smirnov probabilities of each bin. Monte-Carlo simulations show that the test is mostly sensitive to the density parameter, but, under certain conditions, it also sets constraints on the space curvature and, to a lower extent, on the cosmological constant. Cross-tests between power law and exponential luminosity evolution laws are performed, showing that the functional form of luminosity evolution does not affect substantially the probabilities in the parameter space ({OMEGA}_0_, {LAMBDA}). The efficiency of the test applied to two kinds of simulated quasar samples is examined: large number QSO sample, but limited to redshifts z<2.2 or smaller in QSO number, but with higher a redshift limit. Two observational strategies are compared, aimed at the construction of such samples with the future instrumentation of the VLT. Finally, the test is applied to the UVX sample of Boyle et al. (1990MNRAS.243....1B). A low matter density, and a flat Universe without cosmological constant, are rejected: 0.2<{OMEGA}<0.8 within the 95% confidence level.
An improved classification of foci for carcinogenicity testing by statistical descriptors.
Callegaro, Giulia; Stefanini, Federico Mattia; Colacci, Annamaria; Vaccari, Monica; Urani, Chiara
2015-10-01
Carcinogenesis is a multi-step process involving genetic alterations and non-genotoxic mechanisms. The in vitro cell transformation assay (CTA) is a promising tool for both genotoxic and non-genotoxic carcinogenesis. CTA relies on the ability of cells (e.g. BALB/c 3T3 mouse embryo fibroblasts) to develop a transformed phenotype after the treatment with suspected carcinogens. The classification of the transformed phenotype is based on coded morphological features, which are scored under a light microscope by trained experts. This procedure is time-consuming and somewhat prone to subjectivity. Herewith we provide a promising approach based on image analysis to support the scoring of malignant foci in BALB/c 3T3 CTA. The image analysis system is a quantitative approach, based on measuring features of malignant foci: dimension, multilayered growth, and invasivity into the surrounding monolayer of non-transformed cells. A logistic regression model was developed to estimate the probability for each focus to be transformed as a function of three statistical image descriptors. The estimated sensitivity of the derived classifier (untransformed against Type III) was 0.9, with an Area Under the Curve (AUC) value equal to 0.90 under the Receiver Operating Characteristics (ROC) curve. PMID:26183914
NASA Astrophysics Data System (ADS)
Pater, Liana; Miclea, Şerban; Izvercian, Monica
2016-06-01
This paper considers the impact of SMEs' annual turnover upon its marketing activities (in terms of marketing responsibility, strategic planning and budgeting). Empirical results and literature reviews unveil that SMEs managers incline to partake in planned and profitable marketing activities, depending on their turnover's level. Thus, using the collected data form 131 Romanian SMEs managers, we have applied the Chi-Square Test in order to validate or invalidate three research assumptions (hypotheses), created starting from the empirical and literature findings.
Cohn, T.A.; England, J.F.; Berenbrock, C.E.; Mason, R.R.; Stedinger, J.R.; Lamontagne, J.R.
2013-01-01
he Grubbs-Beck test is recommended by the federal guidelines for detection of low outliers in flood flow frequency computation in the United States. This paper presents a generalization of the Grubbs-Beck test for normal data (similar to the Rosner (1983) test; see also Spencer and McCuen (1996)) that can provide a consistent standard for identifying multiple potentially influential low flows. In cases where low outliers have been identified, they can be represented as “less-than” values, and a frequency distribution can be developed using censored-data statistical techniques, such as the Expected Moments Algorithm. This approach can improve the fit of the right-hand tail of a frequency distribution and provide protection from lack-of-fit due to unimportant but potentially influential low flows (PILFs) in a flood series, thus making the flood frequency analysis procedure more robust.
Lew, Bartosz
2008-08-15
We introduce and analyze a method for testing statistical isotropy and Gaussianity and apply it to the Wilkinson Microwave Anisotropy Probe (WMAP) cosmic microwave background (CMB) foreground reduced temperature maps. We also test cross-channel difference maps to constrain levels of residual foreground contamination and systematic uncertainties. We divide the sky into regions of varying size and shape and measure the first four moments of the one-point distribution within these regions, and using their simulated spatial distributions we test the statistical isotropy and Gaussianity hypotheses. By randomly varying orientations of these regions, we sample the underlying CMB field in a new manner, that offers a richer exploration of the data content, and avoids possible biasing due to a single choice of sky division. In our analysis we account for all two-point correlations between different regions and also show the impact on the results when these correlations are neglected. The statistical significance is assessed via comparison with realistic Monte Carlo simulations. We find the three-year WMAP maps to agree well with the isotropic, Gaussian random field simulations as probed by regions corresponding to the angular scales ranging from 6 Degree-Sign to 30 Degree-Sign at 68% confidence level (CL). We report a strong, anomalous (99.8% CL) dipole 'excess' in the V band of the three-year WMAP data and also in the V band of the WMAP five-year data (99.3% CL). Using our statistics, we notice large scale hemispherical power asymmetry, and find that it is not highly statistically significant in the WMAP three-year data ( Less-Than-Or-Equivalent-To 97%) at scales l{<=}40. The significance is even smaller if multipoles up to l=1024 are considered ({approx}90% CL). We give constraints on the amplitude of the previously proposed CMB dipole modulation field parameter. We find some hints of foreground contamination in the form of a locally strong, anomalous kurtosis excess in
Davis-Sharts, J
1986-10-01
Maslow's hierarchy of basic human needs provides a major theoretical framework in nursing science. The purpose of this study was to empirically test Maslow's need theory, specifically at the levels of physiological and security needs, using a hologeistic comparative method. Thirty cultures taken from the 60 cultural units in the Health Relations Area Files (HRAF) Probability Sample were found to have data available for examining hypotheses about thermoregulatory (physiological) and protective (security) behaviors practiced prior to sleep onset. The findings demonstrate there is initial worldwide empirical evidence to support Maslow's need hierarchy.
Innan, Hideki; Zhang, Kangyu; Marjoram, Paul; Tavaré, Simon; Rosenberg, Noah A.
2005-01-01
Several tests of neutral evolution employ the observed number of segregating sites and properties of the haplotype frequency distribution as summary statistics and use simulations to obtain rejection probabilities. Here we develop a “haplotype configuration test” of neutrality (HCT) based on the full haplotype frequency distribution. To enable exact computation of rejection probabilities for small samples, we derive a recursion under the standard coalescent model for the joint distribution of the haplotype frequencies and the number of segregating sites. For larger samples, we consider simulation-based approaches. The utility of the HCT is demonstrated in simulations of alternative models and in application to data from Drosophila melanogaster. PMID:15654103
NASA Astrophysics Data System (ADS)
Verschuur, Gerrit L.
2014-06-01
The archive of IRIS, PLANCK and WMAP data available at the IRSA website of IPAC allows the apparent associations between galactic neutral hydrogen (HI) features and small-scale structure in WMAP and PLANCK data to be closely examined. In addition, HI new observations made with the Green Bank Telescope are used to perform a statistical test of putative associations. It is concluded that attention should be paid to the possibility that some of the small-scale structure found in WMAP and PLANCK data harbors the signature of a previously unrecognized source of high-frequency continuum emission in the Galaxy.
NASA Astrophysics Data System (ADS)
Nosedal-Sanchez, Alvaro; Jackson, Charles S.; Huerta, Gabriel
2016-07-01
A new test statistic for climate model evaluation has been developed that potentially mitigates some of the limitations that exist for observing and representing field and space dependencies of climate phenomena. Traditionally such dependencies have been ignored when climate models have been evaluated against observational data, which makes it difficult to assess whether any given model is simulating observed climate for the right reasons. The new statistic uses Gaussian Markov random fields for estimating field and space dependencies within a first-order grid point neighborhood structure. We illustrate the ability of Gaussian Markov random fields to represent empirical estimates of field and space covariances using "witch hat" graphs. We further use the new statistic to evaluate the tropical response of a climate model (CAM3.1) to changes in two parameters important to its representation of cloud and precipitation physics. Overall, the inclusion of dependency information did not alter significantly the recognition of those regions of parameter space that best approximated observations. However, there were some qualitative differences in the shape of the response surface that suggest how such a measure could affect estimates of model uncertainty.
Nosedal-Sanchez, Alvaro; Jackson, Charles S.; Huerta, Gabriel
2016-07-20
A new test statistic for climate model evaluation has been developed that potentially mitigates some of the limitations that exist for observing and representing field and space dependencies of climate phenomena. Traditionally such dependencies have been ignored when climate models have been evaluated against observational data, which makes it difficult to assess whether any given model is simulating observed climate for the right reasons. The new statistic uses Gaussian Markov random fields for estimating field and space dependencies within a first-order grid point neighborhood structure. We illustrate the ability of Gaussian Markov random fields to represent empirical estimates of fieldmore » and space covariances using "witch hat" graphs. We further use the new statistic to evaluate the tropical response of a climate model (CAM3.1) to changes in two parameters important to its representation of cloud and precipitation physics. Overall, the inclusion of dependency information did not alter significantly the recognition of those regions of parameter space that best approximated observations. However, there were some qualitative differences in the shape of the response surface that suggest how such a measure could affect estimates of model uncertainty.« less
Statistically small effects of the Implicit Association Test can have societally large effects.
Greenwald, Anthony G; Banaji, Mahzarin R; Nosek, Brian A
2015-04-01
Greenwald, Poehlman, Uhlmann, and Banaji (2009; GPUB hereafter) reported an average predictive validity correlation of r̄ = .236 for Implicit Association Test (IAT) measures involving Black-White racial attitudes and stereotypes. Oswald, Mitchell, Blanton, Jaccard, and Tetlock (2013; OMBJT) reported a lower aggregate figure for correlations involving IAT measures (r̄ = .148). The difference between the estimates of the 2 reviews was due mostly to their use of different policies for including effect sizes. GPUB limited their study to findings that assessed theoretically expected attitude-behavior and stereotype-judgment correlations along with others that the authors expected to show positive correlations. OMBJT included a substantial minority of correlations for which there was no theoretical expectation of a predictive relationship. Regardless of inclusion policy, both meta-analyses estimated aggregate correlational effect sizes that were large enough to explain discriminatory impacts that are societally significant either because they can affect many people simultaneously or because they can repeatedly affect single persons. PMID:25402677
Statistically small effects of the Implicit Association Test can have societally large effects.
Greenwald, Anthony G; Banaji, Mahzarin R; Nosek, Brian A
2015-04-01
Greenwald, Poehlman, Uhlmann, and Banaji (2009; GPUB hereafter) reported an average predictive validity correlation of r̄ = .236 for Implicit Association Test (IAT) measures involving Black-White racial attitudes and stereotypes. Oswald, Mitchell, Blanton, Jaccard, and Tetlock (2013; OMBJT) reported a lower aggregate figure for correlations involving IAT measures (r̄ = .148). The difference between the estimates of the 2 reviews was due mostly to their use of different policies for including effect sizes. GPUB limited their study to findings that assessed theoretically expected attitude-behavior and stereotype-judgment correlations along with others that the authors expected to show positive correlations. OMBJT included a substantial minority of correlations for which there was no theoretical expectation of a predictive relationship. Regardless of inclusion policy, both meta-analyses estimated aggregate correlational effect sizes that were large enough to explain discriminatory impacts that are societally significant either because they can affect many people simultaneously or because they can repeatedly affect single persons.
Edwards, T.B.
2000-01-20
The Chemical and Hydrogen Technology Section (CHT) of the Savannah River Technology Center (SRTC) has conducted a series of gas generation tests in support of the revision of the safety analysis report for packaging (SARP) for the 9975 container, developed at the Savannah River Site (SRS). The Packaging and Transportation Group of SRTC is coordinating the revision to this SARP. A Task Technical and Quality Assurance Plan directing this work was issued by CHT in February 1999. Initially, the primary interest in this testing was hydrogen generation. From these ``gas generation tests can be tracked in real-time by measuring the pressure of a sealed container of the materials being studied. Because multiple gas phase reactions are produced in the radiation field of the sample, material pressure measurements do not necessarily define the quantity of H{sub 2} generated. However, the change in total molecules of gas can be calculated using the ideal gas law from the pressure measurement, known container volume and sample temperature. A measurement of the actual headspace gases must be completed to calculate the H{sub 2} generation rate for a particular sample.'' As the results from these tests were reviewed, however, questions arose regarding the oxygen in the headspace gases. Specifically, do the data from some tests indicate that oxygen was generated for those tests? And do the data for other tests indicate that the oxygen was depleted for them? A statistical analysis of the oxygen data derived from these tests is provided in this report to help answer these questions.
Burr, Tom; Hamada, Michael S.; Ticknor, Larry; Sprinkle, James
2015-01-01
The aim of nuclear safeguards is to ensure that special nuclear material is used for peaceful purposes. Historically, nuclear material accounting (NMA) has provided the quantitative basis for monitoring for nuclear material loss or diversion, and process monitoring (PM) data is collected by the operator to monitor the process. PM data typically support NMA in various ways, often by providing a basis to estimate some of the in-process nuclear material inventory. We develop options for combining PM residuals and NMA residuals (residual = measurement - prediction), using a hybrid of period-driven and data-driven hypothesis testing. The modified statistical tests canmore » be used on time series of NMA residuals (the NMA residual is the familiar material balance), or on a combination of PM and NMA residuals. The PM residuals can be generated on a fixed time schedule or as events occur.« less
Burr, Tom; Hamada, Michael S.; Ticknor, Larry; Sprinkle, James
2015-01-01
The aim of nuclear safeguards is to ensure that special nuclear material is used for peaceful purposes. Historically, nuclear material accounting (NMA) has provided the quantitative basis for monitoring for nuclear material loss or diversion, and process monitoring (PM) data is collected by the operator to monitor the process. PM data typically support NMA in various ways, often by providing a basis to estimate some of the in-process nuclear material inventory. We develop options for combining PM residuals and NMA residuals (residual = measurement - prediction), using a hybrid of period-driven and data-driven hypothesis testing. The modified statistical tests can be used on time series of NMA residuals (the NMA residual is the familiar material balance), or on a combination of PM and NMA residuals. The PM residuals can be generated on a fixed time schedule or as events occur.
Long-term trend in patch test reactions: a 32-year statistical overview (1970-2002), part II.
Tudela, Emilie; MacPherson, Cora; Maibach, Howard I
2008-01-01
Allergic contact dermatitis remains an important problem worldwide. The objective of this study was to analyze patch test positivity trends of the North American Contact Dermatitis Group. Publications from 1970 to 2002 were reviewed and re-analyzed. Statistical significance was determined with a Cochran-Armitage trend test. We observed a significant increase in positive reactions with carbamates, balsam of Peru, thimerosal, formaldehyde, imidazolidinyl urea, and methyldibromoglutaronitrile. The rates of positive reactions to Dimethylol dimethyl (DMDM) hydantoin, diazolidinyl urea, and methylchloroisothiazolone/methylisothiazolone remained unchanged. We showed a significant decrease in positive reactions for all other allergens. These data provide challenges in public health--for industry, government, and medicine--to decrease the frequency of allergic contact dermatitis. However, the complexities of evaluating a 32-year analysis are numerous, so the data should be interpreted with caution and within the context of this work.
NASA Technical Reports Server (NTRS)
Matney, Mark
2011-01-01
A number of statistical tools have been developed over the years for assessing the risk of reentering objects to human populations. These tools make use of the characteristics (e.g., mass, material, shape, size) of debris that are predicted by aerothermal models to survive reentry. The statistical tools use this information to compute the probability that one or more of the surviving debris might hit a person on the ground and cause one or more casualties. The statistical portion of the analysis relies on a number of assumptions about how the debris footprint and the human population are distributed in latitude and longitude, and how to use that information to arrive at realistic risk numbers. Because this information is used in making policy and engineering decisions, it is important that these assumptions be tested using empirical data. This study uses the latest database of known uncontrolled reentry locations measured by the United States Department of Defense. The predicted ground footprint distributions of these objects are based on the theory that their orbits behave basically like simple Kepler orbits. However, there are a number of factors in the final stages of reentry - including the effects of gravitational harmonics, the effects of the Earth s equatorial bulge on the atmosphere, and the rotation of the Earth and atmosphere - that could cause them to diverge from simple Kepler orbit behavior and possibly change the probability of reentering over a given location. In this paper, the measured latitude and longitude distributions of these objects are directly compared with the predicted distributions, providing a fundamental empirical test of the model assumptions.
Xiao, Qingtai; Xu, Jianxin; Wang, Hua
2016-08-16
A new index, the estimate of the error variance, which can be used to quantify the evolution of the flow patterns when multiphase components or tracers are difficultly distinguishable, was proposed. The homogeneity degree of the luminance space distribution behind the viewing windows in the direct contact boiling heat transfer process was explored. With image analysis and a linear statistical model, the F-test of the statistical analysis was used to test whether the light was uniform, and a non-linear method was used to determine the direction and position of a fixed source light. The experimental results showed that the inflection point of the new index was approximately equal to the mixing time. The new index has been popularized and applied to a multiphase macro mixing process by top blowing in a stirred tank. Moreover, a general quantifying model was introduced for demonstrating the relationship between the flow patterns of the bubble swarms and heat transfer. The results can be applied to investigate other mixing processes that are very difficult to recognize the target.
NASA Astrophysics Data System (ADS)
Xiao, Qingtai; Xu, Jianxin; Wang, Hua
2016-08-01
A new index, the estimate of the error variance, which can be used to quantify the evolution of the flow patterns when multiphase components or tracers are difficultly distinguishable, was proposed. The homogeneity degree of the luminance space distribution behind the viewing windows in the direct contact boiling heat transfer process was explored. With image analysis and a linear statistical model, the F-test of the statistical analysis was used to test whether the light was uniform, and a non-linear method was used to determine the direction and position of a fixed source light. The experimental results showed that the inflection point of the new index was approximately equal to the mixing time. The new index has been popularized and applied to a multiphase macro mixing process by top blowing in a stirred tank. Moreover, a general quantifying model was introduced for demonstrating the relationship between the flow patterns of the bubble swarms and heat transfer. The results can be applied to investigate other mixing processes that are very difficult to recognize the target.
Xiao, Qingtai; Xu, Jianxin; Wang, Hua
2016-01-01
A new index, the estimate of the error variance, which can be used to quantify the evolution of the flow patterns when multiphase components or tracers are difficultly distinguishable, was proposed. The homogeneity degree of the luminance space distribution behind the viewing windows in the direct contact boiling heat transfer process was explored. With image analysis and a linear statistical model, the F-test of the statistical analysis was used to test whether the light was uniform, and a non-linear method was used to determine the direction and position of a fixed source light. The experimental results showed that the inflection point of the new index was approximately equal to the mixing time. The new index has been popularized and applied to a multiphase macro mixing process by top blowing in a stirred tank. Moreover, a general quantifying model was introduced for demonstrating the relationship between the flow patterns of the bubble swarms and heat transfer. The results can be applied to investigate other mixing processes that are very difficult to recognize the target. PMID:27527065
Chen, W M; Deng, H W
2001-07-01
Transmission disequilibrium test (TDT) is a nuclear family-based analysis that can test linkage in the presence of association. It has gained extensive attention in theoretical investigation and in practical application; in both cases, the accuracy and generality of the power computation of the TDT are crucial. Despite extensive investigations, previous approaches for computing the statistical power of the TDT are neither accurate nor general. In this paper, we develop a general and highly accurate approach to analytically compute the power of the TDT. We compare the results from our approach with those from several other recent papers, all against the results obtained from computer simulations. We show that the results computed from our approach are more accurate than or at least the same as those from other approaches. More importantly, our approach can handle various situations, which include (1) families that consist of one or more children and that have any configuration of affected and nonaffected sibs; (2) families ascertained through the affection status of parent(s); (3) any mixed sample with different types of families in (1) and (2); (4) the marker locus is not a disease susceptibility locus; and (5) existence of allelic heterogeneity. We implement this approach in a user-friendly computer program: TDT Power Calculator. Its applications are demonstrated. The approach and the program developed here should be significant for theoreticians to accurately investigate the statistical power of the TDT in various situations, and for empirical geneticists to plan efficient studies using the TDT.
Xiao, Qingtai; Xu, Jianxin; Wang, Hua
2016-01-01
A new index, the estimate of the error variance, which can be used to quantify the evolution of the flow patterns when multiphase components or tracers are difficultly distinguishable, was proposed. The homogeneity degree of the luminance space distribution behind the viewing windows in the direct contact boiling heat transfer process was explored. With image analysis and a linear statistical model, the F-test of the statistical analysis was used to test whether the light was uniform, and a non-linear method was used to determine the direction and position of a fixed source light. The experimental results showed that the inflection point of the new index was approximately equal to the mixing time. The new index has been popularized and applied to a multiphase macro mixing process by top blowing in a stirred tank. Moreover, a general quantifying model was introduced for demonstrating the relationship between the flow patterns of the bubble swarms and heat transfer. The results can be applied to investigate other mixing processes that are very difficult to recognize the target. PMID:27527065
NASA Astrophysics Data System (ADS)
Pedretti, D.; Fernandez-Garcia, D.; Bolster, D.; Sanchez-Vila, X.; Benson, D.
2012-04-01
For risk assessment and adequate decision making regarding remediation strategies in contaminated aquifers, solute fate in the subsurface must be modeled correctly. In practical situations, hydrodynamic transport parameters are obtained by fitting procedures, that aim to mathematically reproduce solute breakthrough (BTC) observed in the field during tracer tests. In recent years, several methods have been proposed (curve-types, moments, nonlocal formulations) but none of them combine the two main characteristic effects of convergent flow tracer tests (which are the most used tests in the practice): the intrinsic non-stationarity of the convergent flow to a well and the ubiquitous multiscale hydraulic heterogeneity of geological formations. These two effects separately have been accounted for by a lot of methods that appear to work well. Here, we investigate both effects at the same time via numerical analysis. We focus on the influence that measurable statistical properties of the aquifers (such as the variance and the statistical geometry of correlation scales) have on the shape of BTCs measured at the pumping well during convergent flow tracer tests. We built synthetic multigaussian 3D fields of heterogeneous hydraulic conductivity fields with variable statistics. A well is located in the center of the domain to reproduce a forced gradient towards it. Constant-head values are imposed on the boundaries of the domains, which have 251x251x100 cells. Injections of solutes take place by releasing particles at different distances from the well and using a random walk particle tracking scheme with constant local coefficient of dispersivity. The results show that BTCs partially display the typical anomalous behavior that has been commonly referred to as the effect of heterogeneity and connectivity (early and late arrival times of solute differ from the one predicted by local formulations). Among the most salient features, the behaviors of BTCs after the peak (the slope
Kontos, Despina; Megalooikonomou, Vasileios; Gee, James C.
2009-01-01
Summary Objective We evaluate the feasibility of applying dynamic recursive partitioning (DRP), an image analysis technique, to perform morphometric analysis. We apply DRP to detect and characterize discriminative morphometric characteristics between anatomical brain structures from different groups of subjects. Our method reduces the number of statistical tests, commonly required by pixel-wise statistics, alleviating the effect of the multiple comparison problem. Methods and Materials The main idea of DRP is to partition the two-dimensional (2D) image adaptively into progressively smaller sub-regions until statistically significant discriminative regions are detected. The partitioning process is guided by statistical tests applied on groups of pixels. By performing statistical tests on groups of pixels rather than on individual pixels, the number of statistical tests is effectively reduced. This reduction of statistical tests restricts the effect of the multiple comparison problem (i.e. type-I error). We demonstrate an application of DRP for detecting gender-related morphometric differentiation of the corpus callosum. DRP was applied to template deformation fields computed from registered magnetic resonance images of the corpus callosum in order to detect regions of significant expansion or contraction between female and male subjects. Results DRP was able to detect regions comparable to those of pixel-wise analysis, while reducing the number of required statistical tests up to almost 50%. The detected regions were in agreement with findings previously reported in the literature. Statistically significant discriminative morphological variability was detected in the posterior corpus callosum region, the isthmus and the anterior corpus callosum. In addition, by operating on groups of pixels, DRP appears to be less prone to detecting spatially diffused and isolated outlier pixels as significant. Conclusion DRP can be a viable approach for detecting discriminative
Kawamura, Kunio; Abe, Hiroshi
2004-01-01
It is obvious that, in the media fill test and process simulation test, positive numbers in total fills should not have any significant difference from zero or asepsis. There are many reports concerning the definition of "sterility" or "asepsis." However, any scientific and practical methods to demonstrate "no significant difference from zero" have not been reported up to now. The existing criteria, such as "less than 0.1%," "less than 0.05%," and "less than two positives" are not appropriate to assure the integrity of processes, and sometimes lead to erroneous results. The purpose of this report is to demonstrate novel, reasonable and practical methods and criteria based on scientific and statistical consideration. According to the ISO 13408-1 Aseptic Processing of Health Care Products, Part 1 (1998), General Requirement for Aseptic Processing, the action level for the number of positive units in media fill tests is specified as 0.1%, and the alert level is 0.05%. In this paper it is shown that the existing ISO standard and other official methods are inappropriate in that zero contaminated units (sterile product) is outside the confidence range of probable distribution of contaminated units, even though the contaminated units are less than 0.1% in larger numbers of fills, and even less than 0.05%. This indicates that the limit of 0.1% or 0.05% is inappropriate in cases of larger numbers of fills. For sterile products, the number of contaminated units other than "zero" at the statistical confidence range must be judged to be contaminated units in process and as non-sterile. In order to harmonize this criteria-"no significant difference from zero"-with the existing criteria, the new criteria may be combined with only the existing criteria of 0.05% in smaller number of fills.
Zhang Shuangnan; Xie Yi
2012-10-01
We test models for the evolution of neutron star (NS) magnetic fields (B). Our model for the evolution of the NS spin is taken from an analysis of pulsar timing noise presented by Hobbs et al.. We first test the standard model of a pulsar's magnetosphere in which B does not change with time and magnetic dipole radiation is assumed to dominate the pulsar's spin-down. We find that this model fails to predict both the magnitudes and signs of the second derivatives of the spin frequencies ({nu}-double dot). We then construct a phenomenological model of the evolution of B, which contains a long-term decay (LTD) modulated by short-term oscillations; a pulsar's spin is thus modified by its B-evolution. We find that an exponential LTD is not favored by the observed statistical properties of {nu}-double dot for young pulsars and fails to explain the fact that {nu}-double dot is negative for roughly half of the old pulsars. A simple power-law LTD can explain all the observed statistical properties of {nu}-double dot. Finally, we discuss some physical implications of our results to models of the B-decay of NSs and suggest reliable determination of the true ages of many young NSs is needed, in order to constrain further the physical mechanisms of their B-decay. Our model can be further tested with the measured evolutions of {nu}-dot and {nu}-double dot for an individual pulsar; the decay index, oscillation amplitude, and period can also be determined this way for the pulsar.
NASA Technical Reports Server (NTRS)
Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James
2014-01-01
Do you have elevated p-values? Is the data analysis process getting you down? Do you experience anxiety when you need to respond to criticism of statistical methods in your manuscript? You may be suffering from Insufficient Statistical Support Syndrome (ISSS). For symptomatic relief of ISSS, come for a free consultation with JSC biostatisticians at our help desk during the poster sessions at the HRP Investigators Workshop. Get answers to common questions about sample size, missing data, multiple testing, when to trust the results of your analyses and more. Side effects may include sudden loss of statistics anxiety, improved interpretation of your data, and increased confidence in your results.
ERIC Educational Resources Information Center
Meijer, Rob R.; van Krimpen-Stoop, Edith M. L. A.
In this study a cumulative-sum (CUSUM) procedure from the theory of Statistical Process Control was modified and applied in the context of person-fit analysis in a computerized adaptive testing (CAT) environment. Six person-fit statistics were proposed using the CUSUM procedure, and three of them could be used to investigate the CAT in online test…
Mulhall, Declan
2009-09-15
The {delta}{sub 3}(L) statistic is studied as a tool to detect missing levels in the neutron resonance data where two sequences are present. These systems are problematic because there is no level repulsion, and the resonances can be too close to resolve. {delta}{sub 3}(L) is a measure of the fluctuations in the number of levels in an interval of length L on the energy axis. The method used is tested on ensembles of mixed Gaussian orthogonal ensemble spectra, with a known fraction of levels (x%) randomly depleted, and can accurately return x. The accuracy of the method as a function of spectrum size is established. The method is used on neutron resonance data for 11 isotopes with either s-wave neutrons on odd-A isotopes, or p-wave neutrons on even-A isotopes. The method compares favorably with a maximum likelihood method applied to the level spacing distribution. Nuclear data ensembles were made from 20 isotopes in total, and their {delta}{sub 3}(L) statistics are discussed in the context of random matrix theory.
NASA Astrophysics Data System (ADS)
Doubrovine, Pavel V.; Steinberger, Bernhard; Torsvik, Trond H.
2016-03-01
Absolute reconstructions of large igneous provinces (LIPs) for the past 300 Ma reveal a remarkable spatial pattern suggesting that almost all LIPs have erupted over the margins of the two large-scale structures in the Earth's lower mantle commonly referred to as the Large Low Shear-wave Velocity Provinces (LLSVPs). This correlation suggests that mantle plumes that have triggered LIP eruptions rose from the margins of LLSVPs, implying long-term stability of these structures and suggesting that they may be chemically distinct from the bulk of the mantle. Yet, some researchers consider the LLSVPs to be purely thermal upwellings, arguing that the observed distribution of LIPs can be explained by plumes randomly forming over the entire areas of LLSVPs. Here we examine the correlation between the LIPs and LLSVPs using nonparametric statistical tests, updated plate reconstructions, and a large number of alternative definitions of LLSVPs based on seismic tomography. We show that probability models assuming plume sources originating at the margins of LLSVPs adequately explain the observed distribution of reconstructed LIPs. In contrast, we find strong evidence against the models seeking to link LIPs with plumes randomly forming over the entire LLSVP areas. However, the hypothesis proposing that the correlation can be explained by plumes randomly forming over a larger area of slower-than-average shear wave velocities in the lowermost mantle cannot be ruled out formally. Our analysis suggests that there is no statistically sound reason for questioning the hypothesis that the LIPs correlate with the margins of LLSVP globally.
NASA Astrophysics Data System (ADS)
Evans, Mark
2016-10-01
A new parametric approach, termed the Wilshire equations, offers the realistic potential of being able to accurately lift materials operating at in-service conditions from accelerated test results lasting no more than 5000 hours. The success of this approach can be attributed to a well-defined linear relationship that appears to exist between various creep properties and a log transformation of the normalized stress. However, these linear trends are subject to discontinuities, the number of which appears to differ from material to material. These discontinuities have until now been (1) treated as abrupt in nature and (2) identified by eye from an inspection of simple graphical plots of the data. This article puts forward a statistical test for determining the correct number of discontinuities present within a creep data set and a method for allowing these discontinuities to occur more gradually, so that the methodology is more in line with the accepted view as to how creep mechanisms evolve with changing test conditions. These two developments are fully illustrated using creep data sets on two steel alloys. When these new procedures are applied to these steel alloys, not only do they produce more accurate and realistic looking long-term predictions of the minimum creep rate, but they also lead to different conclusions about the mechanisms determining the rates of creep from those originally put forward by Wilshire.
Singh, K.P.; Iulianetti, K.M.; Scott, B.H.
1994-12-31
This paper describes the methodology to ascertain the heat transfer capability of a tubular heat exchanger from steady state field test data. Periodic assessment of the heat duty capability of heat exchangers utilizing a fluid stream capable of inducing appreciable fouling and deemed to be critical to safety in operating nuclear power plants has become a common practice in the wake of USNRC`s issuance of the Generic Letter 89-13. Since the measured test data invariably have a measure of uncertainty due to bias in the measurement instrumentation and errors in the measuring process and the heat transfer coefficient can only be calculated as an approximate value with an associated uncertainty, the calculation of the fouling factor must utilize concepts from statistics of multivariate random phenomena. For simplicity, and without loss of appreciable accuracy, all variables and measurement parameters are assumed to follow Gaussian probability distribution. The solution process permits and utilizes redundant measurements to improve the quality of the result. Although work was specifically carried out to deal with the thermal performance safety issues raised by the US Nuclear Regulatory Commission in 1989, it can be utilized in the performance assessment of any heat exchanger in any industrial application where in-situ testing is carried out. The methodology described herein is implemented in the computer code ST{_}XPERT, whose features are also described in this paper.
Forbes, Valery E; Aufderheide, John; Warbritton, Ryan; van der Hoeven, Nelly; Caspers, Norbert
2007-03-01
This study presents results of the effects of bisphenol A (BPA) on adult egg production, egg hatchability, egg development rates and juvenile growth rates in the freshwater gastropod, Marisa cornuarietis. We observed no adult mortality, substantial inter-snail variability in reproductive output, and no effects of BPA on reproduction during 12 weeks of exposure to 0, 0.1, 1.0, 16, 160 or 640 microg/L BPA. We observed no effects of BPA on egg hatchability or timing of egg hatching. Juveniles showed good growth in the control and all treatments, and there were no significant effects of BPA on this endpoint. Our results do not support previous claims of enhanced reproduction in Marisa cornuarietis in response to exposure to BPA. Statistical power analysis indicated high levels of inter-snail variability in the measured endpoints and highlighted the need for sufficient replication when testing treatment effects on reproduction in M. cornuarietis with adequate power.
NASA Astrophysics Data System (ADS)
Zhao, J. Q.; Yang, J.; Li, P. X.; Liu, M. Y.; Shi, Y. M.
2016-06-01
Accurate and timely change detection of Earth's surface features is extremely important for understanding relationships and interactions between people and natural phenomena. Many traditional methods of change detection only use a part of polarization information and the supervised threshold selection. Those methods are insufficiency and time-costing. In this paper, we present a novel unsupervised change-detection method based on quad-polarimetric SAR data and automatic threshold selection to solve the problem of change detection. First, speckle noise is removed for the two registered SAR images. Second, the similarity measure is calculated by the test statistic, and automatic threshold selection of KI is introduced to obtain the change map. The efficiency of the proposed method is demonstrated by the quad-pol SAR images acquired by Radarsat-2 over Wuhan of China.
ERIC Educational Resources Information Center
Qasem, Mamun Ali Naji; Altrairy, Abdulrhman; Govil, Punita
2012-01-01
This research has aimed at constructing Criterion Referenced Test to measure the statistical competencies of the Post-graduate Students in Education Colleges in Yemeni Universities, at examining the validity of the test's grades (the descriptive validity and the Domain Selection Validity), at examining the test's grades Reliability according to…
Andersen, C E; Ulbak, K; Damkjaer, A; Kirkegaard, P; Gravesen, P
2001-05-14
In Denmark, a new survey of indoor radon-222 has been carried out, 1-year alpha track measurements (CR-39) have been made in 3019 single-family houses. There are from 3 to 23 house measurements in each of the 275 municipalities. Within each municipality, houses have been selected randomly. One important outcome of the survey is the prediction of the fraction of houses in each municipality with an annual average radon concentration above 200 Bq m(-3). To obtain the most accurate estimate and to assess the associated uncertainties, a statistical model has been developed. The purpose of this paper is to describe the design of this model, and to report results of model tests. The model is based on a transformation of the data to normality and on analytical (conditionally) unbiased estimators of the quantities of interest. Bayesian statistics are used to minimize the effect of small sample size. In each municipality, the correction is dependent on the fraction of area where sand and gravel is a dominating surface geology. The uncertainty analysis is done with a Monte-Carlo technique. It is demonstrated that the weighted sum of all municipality model estimates of fractions above 200 Bq m(-3) (3.9% with 95%-confidence interval = [3.4,4.5]) is consistent with the weighted sum of the observations for Denmark taken as a whole (4.6% with 95%-confidence interval = [3.8,5.6]). The total number of single-family houses within each municipality is used as weight. Model estimates are also found to be consistent with observations at the level of individual counties. These typically include a few hundred house measurements. These tests indicate that the model is well suited for its purpose.
Wellek, S; Dunkelberg, H
1981-12-01
In Section 1 we discuss the fundamental point that the overall tumour incidence rates observed in long-term tests for carcinogenesis typically are biased by differences in intercurrent mortality. In view of some more recent results from theoretical statistics an application of the random censorship model provides an especially powerful approach to getting along with this difficulty. The main assumptions making up the random censorship model as to be applied to the special case of long-term carcinogenesis assay data are carefully described. A consistent and unbiased method for calculating tumour incidence rates corrected for tumour independent intercurrent mortality from the data of an experiment which satisfies the aforementioned assumptions is provided by the Kaplan-Meier technique. Full computational details of the Kaplan-Meier procedure are presented in Section 2. Section 3 is concerned with significance tests for judging dose effects on standardized tumour induction rates. The stepwise procedure recently developed by Holm is adapted to the multiple comparison of several single doses of a possibly carcinogenic compound to the same control. A significance test specifically designed for the assessment of an increasing dose dependent trend is due to Cox and Tarone. Formulas enabling to an easy performance of the Cox-Tarone test are also explicitly written down. In Section 4 we show how to take advantage of Cox's "proportional hazards model" in establishing approximate dose-response relationships.--In each case the general description of the computational procedure is illustrated by an elaborate real data example from a study (published in the same issue of this journal) on the carcinogenicity of ethylene oxide and 1,2-propylene oxide after subcutaneous administration in mice.
CAP,JEROME S.; TRACEY,BRIAN
1999-11-15
Aerospace payloads, such as satellites, are subjected to vibroacoustic excitation during launch. Sandia's MTI satellite has recently been certified to this environment using a combination of base input random vibration and reverberant acoustic noise. The initial choices for the acoustic and random vibration test specifications were obtained from the launch vehicle Interface Control Document (ICD). In order to tailor the random vibration levels for the laboratory certification testing, it was necessary to determine whether vibration energy was flowing across the launch vehicle interface from the satellite to the launch vehicle or the other direction. For frequencies below 120 Hz this issue was addressed using response limiting techniques based on results from the Coupled Loads Analysis (CLA). However, since the CLA Finite Element Analysis FEA model was only correlated for frequencies below 120 Hz, Statistical Energy Analysis (SEA) was considered to be a better choice for predicting the direction of the energy flow for frequencies above 120 Hz. The existing SEA model of the launch vehicle had been developed using the VibroAcoustic Payload Environment Prediction System (VAPEPS) computer code [1]. Therefore, the satellite would have to be modeled using VAPEPS as well. As is the case for any computational model, the confidence in its predictive capability increases if one can correlate a sample prediction against experimental data. Fortunately, Sandia had the ideal data set for correlating an SEA model of the MTI satellite--the measured response of a realistic assembly to a reverberant acoustic test that was performed during MTI's qualification test series. The first part of this paper will briefly describe the VAPEPS modeling effort and present the results of the correlation study for the VAPEPS model. The second part of this paper will present the results from a study that used a commercial SEA software package [2] to study the effects of in-plane modes and to
Huh, Iksoo; Kwon, Min-Seok; Park, Taesung
2015-01-01
Recent advances in genotyping methodologies have allowed genome-wide association studies (GWAS) to accurately identify genetic variants that associate with common or pathological complex traits. Although most GWAS have focused on associations with single genetic variants, joint identification of multiple genetic variants, and how they interact, is essential for understanding the genetic architecture of complex phenotypic traits. Here, we propose an efficient stepwise method based on the Cochran-Mantel-Haenszel test (for stratified categorical data) to identify causal joint multiple genetic variants in GWAS. This method combines the CMH statistic with a stepwise procedure to detect multiple genetic variants associated with specific categorical traits, using a series of associated I × J contingency tables and a null hypothesis of no phenotype association. Through a new stratification scheme based on the sum of minor allele count criteria, we make the method more feasible for GWAS data having sample sizes of several thousands. We also examine the properties of the proposed stepwise method via simulation studies, and show that the stepwise CMH test performs better than other existing methods (e.g., logistic regression and detection of associations by Markov blanket) for identifying multiple genetic variants. Finally, we apply the proposed approach to two genomic sequencing datasets to detect linked genetic variants associated with bipolar disorder and obesity, respectively. PMID:26406920
Moukadem, Ali; Schmidt, Samuel; Dieterlen, Alain
2015-01-01
This paper considers the problem of classification of the first and the second heart sounds (S1 and S2) under cardiac stress test. The main objective is to classify these sounds without electrocardiogram (ECG) reference and without taking into consideration the systolic and the diastolic time intervals criterion which can become problematic and useless in several real life settings as severe tachycardia and tachyarrhythmia or in the case of subjects being under cardiac stress activity. First, the heart sounds are segmented by using a modified time-frequency based envelope. Then, to distinguish between the first and the second heart sounds, new features, named αopt, β, and γ, based on high order statistics and energy concentration measures of the Stockwell transform (S-transform) are proposed in this study. A study of the variation of the high frequency content of S1 and S2 over the HR (heart rate) is also discussed. The proposed features are validated on a database that contains 2636 S1 and S2 sounds corresponding to 62 heart signals and 8 subjects under cardiac stress test collected from healthy subjects. Results and comparisons with existing methods in the literature show a large superiority for our proposed features. PMID:26089957
NASA Astrophysics Data System (ADS)
Auchmann, Renate; Brönnimann, Stefan; Croci-Maspoli, Mischa
2016-04-01
For the correction of inhomogeneities in sub-daily temperature series, Auchmann and Brönnimann (2012) developed a physics-based model for one specific type of break, i.e. the transition from a Wild screen to a Stevenson screen at one specific station in Basel, Switzerland. The model is based solely on physical considerations, no relationships of the covariates to the differences between the parallel measurements have been investigated. The physics-based model requires detailed information on the screen geometry, the location, and includes a variety of covariates in the model. The model is mainly based on correcting the radiation error, including a modification by ambient wind. In this study we test the application of the model to another station, Zurich, experiencing the same type of transition. Furthermore we compare the performance of the physics based correction to purely statistical correction approaches (constant correction, correcting for annual cycle using spline). In Zurich the Wild screen was replaced in 1954 by the Stevenson screen, from 1954-1960 parallel temperature measurements in both screens were taken, which will be used to assess the performance of the applied corrections. For Zurich the required model input is available (i.e. three times daily observations of wind, cloud cover, pressure and humidity measurements, local times of sunset and sunrise). However, a large number of stations do not measure these additional input data required for the model, which hampers the transferability and applicability of the model to other stations. Hence, we test possible simplifications and generalizations of the model to make it more easily applicable to stations with the same type of inhomogeneity. In a last step we test whether other types of transitions (e.g., from a Stevenson screen to an automated weather system) can be corrected using the principle of a physics-based approach.
Kossobokov, V.G.; Romashkova, L.L.; Keilis-Borok, V. I.; Healy, J.H.
1999-01-01
Algorithms M8 and MSc (i.e., the Mendocino Scenario) were used in a real-time intermediate-term research prediction of the strongest earthquakes in the Circum-Pacific seismic belt. Predictions are made by M8 first. Then, the areas of alarm are reduced by MSc at the cost that some earthquakes are missed in the second approximation of prediction. In 1992-1997, five earthquakes of magnitude 8 and above occurred in the test area: all of them were predicted by M8 and MSc identified correctly the locations of four of them. The space-time volume of the alarms is 36% and 18%, correspondingly, when estimated with a normalized product measure of empirical distribution of epicenters and uniform time. The statistical significance of the achieved results is beyond 99% both for M8 and MSc. For magnitude 7.5 + , 10 out of 19 earthquakes were predicted by M8 in 40% and five were predicted by M8-MSc in 13% of the total volume considered. This implies a significance level of 81% for M8 and 92% for M8-MSc. The lower significance levels might result from a global change in seismic regime in 1993-1996, when the rate of the largest events has doubled and all of them become exclusively normal or reversed faults. The predictions are fully reproducible; the algorithms M8 and MSc in complete formal definitions were published before we started our experiment [Keilis-Borok, V.I., Kossobokov, V.G., 1990. Premonitory activation of seismic flow: Algorithm M8, Phys. Earth and Planet. Inter. 61, 73-83; Kossobokov, V.G., Keilis-Borok, V.I., Smith, S.W., 1990. Localization of intermediate-term earthquake prediction, J. Geophys. Res., 95, 19763-19772; Healy, J.H., Kossobokov, V.G., Dewey, J.W., 1992. A test to evaluate the earthquake prediction algorithm, M8. U.S. Geol. Surv. OFR 92-401]. M8 is available from the IASPEI Software Library [Healy, J.H., Keilis-Borok, V.I., Lee, W.H.K. (Eds.), 1997. Algorithms for Earthquake Statistics and Prediction, Vol. 6. IASPEI Software Library]. ?? 1999 Elsevier
Validity of the Eating Attitude Test among Exercisers.
Lane, Helen J; Lane, Andrew M; Matheson, Hilary
2004-12-01
Theory testing and construct measurement are inextricably linked. To date, no published research has looked at the factorial validity of an existing eating attitude inventory for use with exercisers. The Eating Attitude Test (EAT) is a 26-item measure that yields a single index of disordered eating attitudes. The original factor analysis showed three interrelated factors: Dieting behavior (13-items), oral control (7-items), and bulimia nervosa-food preoccupation (6-items). The primary purpose of the study was to examine the factorial validity of the EAT among a sample of exercisers. The second purpose was to investigate relationships between eating attitudes scores and selected psychological constructs. In stage one, 598 regular exercisers completed the EAT. Confirmatory factor analysis (CFA) was used to test the single-factor, a three-factor model, and a four-factor model, which distinguished bulimia from food pre-occupation. CFA of the single-factor model (RCFI = 0.66, RMSEA = 0.10), the three-factor-model (RCFI = 0.74; RMSEA = 0.09) showed poor model fit. There was marginal fit for the 4-factor model (RCFI = 0.91, RMSEA = 0.06). Results indicated five-items showed poor factor loadings. After these 5-items were discarded, the three models were re-analyzed. CFA results indicated that the single-factor model (RCFI = 0.76, RMSEA = 0.10) and three-factor model (RCFI = 0.82, RMSEA = 0.08) showed poor fit. CFA results for the four-factor model showed acceptable fit indices (RCFI = 0.98, RMSEA = 0.06). Stage two explored relationships between EAT scores, mood, self-esteem, and motivational indices toward exercise in terms of self-determination, enjoyment and competence. Correlation results indicated that depressed mood scores positively correlated with bulimia and dieting scores. Further, dieting was inversely related with self-determination toward exercising. Collectively, findings suggest that a 21-item four-factor model shows promising validity coefficients among
Hollenbeck, John R; DeRue, D Scott; Mannor, Michael
2006-01-01
Comments on the original article "The impact of chief executive officer personality on top management team dynamics: One mechanism by which leadership affects organizational performance", by R. S. Peterson et al.. This comment illustrates how small sample sizes, when combined with many statistical tests, can generate unstable parameter estimates and invalid inferences. Although statistical power for 1 test in a small-sample context is too low, the experimentwise power is often high when many tests are conducted, thus leading to Type I errors that will not replicate when retested. This comment's results show how radically the specific conclusions and inferences in R. S. Peterson, D. B. Smith, P. V. Martorana, and P. D. Owens's (2003) study changed with the inclusion or exclusion of 1 data point. When a more appropriate experimentwise statistical test was applied, the instability in the inferences was eliminated, but all the inferences become nonsignificant, thus changing the positive conclusions.
NASA Astrophysics Data System (ADS)
Chae, Kyu-Hyun; Gong, In-Taek
2015-08-01
Modified Newtonian dynamics (MOND) proposed by Milgrom provides a paradigm alternative to dark matter (DM) that has been successful in fitting and predicting the rich phenomenology of rotating disc galaxies. There have also been attempts to test MOND in dispersion-supported spheroidal early-type galaxies, but it remains unclear whether MOND can fit the various empirical properties of early-type galaxies for the whole ranges of mass and radius. As a way of rigorously testing MOND in elliptical galaxies we calculate the MOND-predicted velocity dispersion profiles (VDPs) in the inner regions of ˜2000 nearly round Sloan Digital Sky Survey elliptical galaxies under a variety of assumptions on velocity dispersion (VD) anisotropy, and then compare the predicted distribution of VDP slopes with the observed distribution in 11 ATLAS3D galaxies selected with essentially the same criteria. We find that the MOND model parametrized with an interpolating function that works well for rotating galaxies can also reproduce the observed distribution of VDP slopes based only on the observed stellar mass distribution without DM or any other galaxy-to-galaxy varying factor. This is remarkable in view that Newtonian dynamics with DM requires a specific amount and/or profile of DM for each galaxy in order to reproduce the observed distribution of VDP slopes. When we analyse non-round galaxy samples using the MOND-based spherical Jeans equation, we do not find any systematic difference in the mean property of the VDP slope distribution compared with the nearly round sample. However, in line with previous studies of MOND through individual analyses of elliptical galaxies, varying MOND interpolating function or VD anisotropy can lead to systematic change in the VDP slope distribution, indicating that a statistical analysis of VDPs can be used to constrain specific MOND models with an accurate measurement of VDP slopes or a prior constraint on VD anisotropy.
Distribution of the two-sample t-test statistic following blinded sample size re-estimation.
Lu, Kaifeng
2016-05-01
We consider the blinded sample size re-estimation based on the simple one-sample variance estimator at an interim analysis. We characterize the exact distribution of the standard two-sample t-test statistic at the final analysis. We describe a simulation algorithm for the evaluation of the probability of rejecting the null hypothesis at given treatment effect. We compare the blinded sample size re-estimation method with two unblinded methods with respect to the empirical type I error, the empirical power, and the empirical distribution of the standard deviation estimator and final sample size. We characterize the type I error inflation across the range of standardized non-inferiority margin for non-inferiority trials, and derive the adjusted significance level to ensure type I error control for given sample size of the internal pilot study. We show that the adjusted significance level increases as the sample size of the internal pilot study increases. Copyright © 2016 John Wiley & Sons, Ltd.
Suner, Aslı; Karakülah, Gökhan; Koşaner, Özgün; Dicle, Oğuz
2015-01-01
The improper use of statistical methods is common in analyzing and interpreting research data in biological and medical sciences. The objective of this study was to develop a decision support tool encompassing the commonly used statistical tests in biomedical research by combining and updating the present decision trees for appropriate statistical test selection. First, the decision trees in textbooks, published articles, and online resources were scrutinized, and a more comprehensive unified one was devised via the integration of 10 distinct decision trees. The questions also in the decision steps were revised by simplifying and enriching of the questions with examples. Then, our decision tree was implemented into the web environment and the tool titled StatXFinder was developed. Finally, usability and satisfaction questionnaires were applied to the users of the tool, and StatXFinder was reorganized in line with the feedback obtained from these questionnaires. StatXFinder provides users with decision support in the selection of 85 distinct parametric and non-parametric statistical tests by directing 44 different yes-no questions. The accuracy rate of the statistical test recommendations obtained by 36 participants, with the cases applied, were 83.3 % for "difficult" tests, and 88.9 % for "easy" tests. The mean system usability score of the tool was found 87.43 ± 10.01 (minimum: 70-maximum: 100). A statistically significant difference could not be seen between total system usability score and participants' attributes (p value >0.05). The User Satisfaction Questionnaire showed that 97.2 % of the participants appreciated the tool, and almost all of the participants (35 of 36) thought of recommending the tool to the others. In conclusion, StatXFinder, can be utilized as an instructional and guiding tool for biomedical researchers with limited statistics knowledge. StatXFinder is freely available at http://webb.deu.edu.tr/tb/statxfinder. PMID:26543767
NASA Astrophysics Data System (ADS)
Wang, H. J.; Shi, W. L.; Chen, X. H.
2006-05-01
The West Development Policy being implemented in China is causing significant land use and land cover (LULC) changes in West China. With the up-to-date satellite database of the Global Land Cover Characteristics Database (GLCCD) that characterizes the lower boundary conditions, the regional climate model RIEMS-TEA is used to simulate possible impacts of the significant LULC variation. The model was run for five continuous three-month periods from 1 June to 1 September of 1993, 1994, 1995, 1996, and 1997, and the results of the five groups are examined by means of a student t-test to identify the statistical significance of regional climate variation. The main results are: (1) The regional climate is affected by the LULC variation because the equilibrium of water and heat transfer in the air-vegetation interface is changed. (2) The integrated impact of the LULC variation on regional climate is not only limited to West China where the LULC varies, but also to some areas in the model domain where the LULC does not vary at all. (3) The East Asian monsoon system and its vertical structure are adjusted by the large scale LULC variation in western China, where the consequences axe the enhancement of the westward water vapor transfer from the east east and the relevant increase of wet-hydrostatic energy in the middle-upper atmospheric layers. (4) The ecological engineering in West China affects significantly the regional climate in Northwest China, North China and the middle-lower reaches of the Yangtze River; there are obvious effects in South, Northeast, and Southwest China, but minor effects in Tibet.
Brethauer, G.E.; Magner, J.E.; Miller, D.R.
1980-05-01
The US Geological Survey/Defense Nuclear Agency Physical-Properties Storage and Retrieval System was used to generate tables displaying the basic statistics of physical-properties data sets sorted according to geologic identification and tunnel complex in Rainier and Aqueduct Mesas. An approximate procedure to statistically evaluate the significance of geologic identifier versus physical-property average value was developed. Results of this procedure indicate that no conclusive consistent relation exists between geologic identifier and physical-properties average value.
Pasaniuc, Bogdan; Zaitlen, Noah; Lettre, Guillaume; Chen, Gary K.; Tandon, Arti; Kao, W. H. Linda; Ruczinski, Ingo; Fornage, Myriam; Siscovick, David S.; Zhu, Xiaofeng; Larkin, Emma; Lange, Leslie A.; Cupples, L. Adrienne; Yang, Qiong; Akylbekova, Ermeg L.; Musani, Solomon K.; Divers, Jasmin; Mychaleckyj, Joe; Li, Mingyao; Papanicolaou, George J.; Millikan, Robert C.; Ambrosone, Christine B.; John, Esther M.; Bernstein, Leslie; Zheng, Wei; Hu, Jennifer J.; Ziegler, Regina G.; Nyante, Sarah J.; Bandera, Elisa V.; Ingles, Sue A.; Press, Michael F.; Chanock, Stephen J.; Deming, Sandra L.; Rodriguez-Gil, Jorge L.; Palmer, Cameron D.; Buxbaum, Sarah; Ekunwe, Lynette; Hirschhorn, Joel N.; Henderson, Brian E.; Myers, Simon; Haiman, Christopher A.; Reich, David; Patterson, Nick; Wilson, James G.; Price, Alkes L.
2011-01-01
While genome-wide association studies (GWAS) have primarily examined populations of European ancestry, more recent studies often involve additional populations, including admixed populations such as African Americans and Latinos. In admixed populations, linkage disequilibrium (LD) exists both at a fine scale in ancestral populations and at a coarse scale (admixture-LD) due to chromosomal segments of distinct ancestry. Disease association statistics in admixed populations have previously considered SNP association (LD mapping) or admixture association (mapping by admixture-LD), but not both. Here, we introduce a new statistical framework for combining SNP and admixture association in case-control studies, as well as methods for local ancestry-aware imputation. We illustrate the gain in statistical power achieved by these methods by analyzing data of 6,209 unrelated African Americans from the CARe project genotyped on the Affymetrix 6.0 chip, in conjunction with both simulated and real phenotypes, as well as by analyzing the FGFR2 locus using breast cancer GWAS data from 5,761 African-American women. We show that, at typed SNPs, our method yields an 8% increase in statistical power for finding disease risk loci compared to the power achieved by standard methods in case-control studies. At imputed SNPs, we observe an 11% increase in statistical power for mapping disease loci when our local ancestry-aware imputation framework and the new scoring statistic are jointly employed. Finally, we show that our method increases statistical power in regions harboring the causal SNP in the case when the causal SNP is untyped and cannot be imputed. Our methods and our publicly available software are broadly applicable to GWAS in admixed populations. PMID:21541012
ERIC Educational Resources Information Center
Osler, James Edward, II
2015-01-01
This monograph provides an epistemological rational for the Accumulative Manifold Validation Analysis [also referred by the acronym "AMOVA"] statistical methodology designed to test psychometric instruments. This form of inquiry is a form of mathematical optimization in the discipline of linear stochastic modelling. AMOVA is an in-depth…
ERIC Educational Resources Information Center
Gómez-Benito, Juana; Hidalgo, Maria Dolores; Zumbo, Bruno D.
2013-01-01
The objective of this article was to find an optimal decision rule for identifying polytomous items with large or moderate amounts of differential functioning. The effectiveness of combining statistical tests with effect size measures was assessed using logistic discriminant function analysis and two effect size measures: R[superscript 2] and…
Trickey, Amber W.; Crosby, Moira E.; Singh, Monika; Dort, Jonathan M.
2014-01-01
Background The application of evidence-based medicine to patient care requires unique skills of the physician. Advancing residents' abilities to accurately evaluate the quality of evidence is built on understanding of fundamental research concepts. The American Board of Surgery In-Training Examination (ABSITE) provides a relevant measure of surgical residents' knowledge of research design and statistics. Objective We implemented a research education curriculum in an independent academic medical center general residency program, and assessed the effect on ABSITE scores. Methods The curriculum consisted of five 1-hour monthly research and statistics lectures. The lectures were presented before the 2012 and 2013 examinations. Forty residents completing ABSITE examinations from 2007 to 2013 were included in the study. Two investigators independently identified research-related item topics from examination summary reports. Correct and incorrect responses were compared precurriculum and postcurriculum. Regression models were calculated to estimate improvement in postcurriculum scores, adjusted for individuals' scores over time and postgraduate year level. Results Residents demonstrated significant improvement in postcurriculum examination scores for research and statistics items. Correct responses increased 27% (P < .001). Residents were 5 times more likely to achieve a perfect score on research and statistics items postcurriculum (P < .001). Conclusions Residents at all levels demonstrated improved research and statistics scores after receiving the curriculum. Because the ABSITE includes a wide spectrum of research topics, sustained improvements suggest a genuine level of understanding that will promote lifelong evaluation and clinical application of the surgical literature. PMID:26140115
ERIC Educational Resources Information Center
Hsiung, Tung-Hsing; Olejnik, Stephen
This study investigated the robustness of the James second-order test (James 1951; Wilcox, 1989) and the univariate F test under a two-factor fixed-effect analysis of variance (ANOVA) model in which cell variances were heterogeneous and/or distributions were nonnormal. With computer-simulated data, Type I error rates and statistical power for the…
Simonson, K.M.
1998-08-01
The rate at which a mine detection system falsely identifies man-made or natural clutter objects as mines is referred to as the system's false alarm rate (FAR). Generally expressed as a rate per unit area or time, the FAR is one of the primary metrics used to gauge system performance. In this report, an overview is given of statistical methods appropriate for the analysis of data relating to FAR. Techniques are presented for determining a suitable size for the clutter collection area, for summarizing the performance of a single sensor, and for comparing different sensors. For readers requiring more thorough coverage of the topics discussed, references to the statistical literature are provided. A companion report addresses statistical issues related to the estimation of mine detection probabilities.
ERIC Educational Resources Information Center
Chalmers, R. Philip; Counsell, Alyssa; Flora, David B.
2016-01-01
Differential test functioning, or DTF, occurs when one or more items in a test demonstrate differential item functioning (DIF) and the aggregate of these effects are witnessed at the test level. In many applications, DTF can be more important than DIF when the overall effects of DIF at the test level can be quantified. However, optimal statistical…
ERIC Educational Resources Information Center
Nevitt, Jonathan; Hancock, Gregory R.
2001-01-01
Evaluated the bootstrap method under varying conditions of nonnormality, sample size, model specification, and number of bootstrap samples drawn from the resampling space. Results for the bootstrap suggest the resampling-based method may be conservative in its control over model rejections, thus having an impact on the statistical power associated…
Henn, Julian; Meindl, Kathrin
2015-03-01
Statistical tests are applied for the detection of systematic errors in data sets from least-squares refinements or other residual-based reconstruction processes. Samples of the residuals of the data are tested against the hypothesis that they belong to the same distribution. For this it is necessary that they show the same mean values and variances within the limits given by statistical fluctuations. When the samples differ significantly from each other, they are not from the same distribution within the limits set by the significance level. Therefore they cannot originate from a single Gaussian function in this case. It is shown that a significance cutoff results in exactly this case. Significance cutoffs are still frequently used in charge-density studies. The tests are applied to artificial data with and without systematic errors and to experimental data from the literature.
ERIC Educational Resources Information Center
Wilkins, M. Elaine
2012-01-01
In 2001, No Child Left Behind introduced the highly qualified status for k-12 teachers, which mandated the successful scores on a series of high-stakes test; within this series is the Pre-Professional Skills Test (PPST) or PRAXIS I. The PPST measures basic k-12 skills for reading, writing, and mathematics. The mathematics sub-test is a national…
Test of the statistical model in Mo96 with the BaF2γ calorimeter DANCE array
NASA Astrophysics Data System (ADS)
Sheets, S. A.; Agvaanluvsan, U.; Becker, J. A.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Parker, W.; Reifarth, R.; Rundberg, R. S.; Sharapov, E. I.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Wu, C. Y.
2009-02-01
The γ-ray cascades following the Mo95(n,γ)Mo96 reaction were studied with the γ calorimeter DANCE (Detector for Advanced Neutron Capture Experiments) consisting of 160 BaF2 scintillation detectors at the Los Alamos Neutron Science Center. The γ-ray energy spectra for different multiplicities were measured for s- and p-wave resonances below 2 keV. The shapes of these spectra were found to be in very good agreement with simulations using the DICEBOX statistical model code. The relevant model parameters used for the level density and photon strength functions were identical with those that provided the best fit of the data from a recent measurement of the thermal Mo95(n,γ)Mo96 reaction with the two-step-cascade method. The reported results strongly suggest that the extreme statistical model works very well in the mass region near A=100.
Test of the statistical model in {sup 96}Mo with the BaF{sub 2}{gamma} calorimeter DANCE array
Sheets, S. A.; Mitchell, G. E.; Agvaanluvsan, U.; Becker, J. A.; Parker, W.; Wu, C. Y.; Becvar, F.; Krticka, M.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Sharapov, E. I.
2009-02-15
The {gamma}-ray cascades following the {sup 95}Mo(n,{gamma}){sup 96}Mo reaction were studied with the {gamma} calorimeter DANCE (Detector for Advanced Neutron Capture Experiments) consisting of 160 BaF{sub 2} scintillation detectors at the Los Alamos Neutron Science Center. The {gamma}-ray energy spectra for different multiplicities were measured for s- and p-wave resonances below 2 keV. The shapes of these spectra were found to be in very good agreement with simulations using the DICEBOX statistical model code. The relevant model parameters used for the level density and photon strength functions were identical with those that provided the best fit of the data from a recent measurement of the thermal {sup 95}Mo(n,{gamma}){sup 96}Mo reaction with the two-step-cascade method. The reported results strongly suggest that the extreme statistical model works very well in the mass region near A=100.
Hsiao, Chiaowen; Liu, Mengya; Stanton, Rick; McGee, Monnie; Qian, Yu; Scheuermann, Richard H
2016-01-01
Flow cytometry (FCM) is a fluorescence-based single-cell experimental technology that is routinely applied in biomedical research for identifying cellular biomarkers of normal physiological responses and abnormal disease states. While many computational methods have been developed that focus on identifying cell populations in individual FCM samples, very few have addressed how the identified cell populations can be matched across samples for comparative analysis. This article presents FlowMap-FR, a novel method for cell population mapping across FCM samples. FlowMap-FR is based on the Friedman-Rafsky nonparametric test statistic (FR statistic), which quantifies the equivalence of multivariate distributions. As applied to FCM data by FlowMap-FR, the FR statistic objectively quantifies the similarity between cell populations based on the shapes, sizes, and positions of fluorescence data distributions in the multidimensional feature space. To test and evaluate the performance of FlowMap-FR, we simulated the kinds of biological and technical sample variations that are commonly observed in FCM data. The results show that FlowMap-FR is able to effectively identify equivalent cell populations between samples under scenarios of proportion differences and modest position shifts. As a statistical test, FlowMap-FR can be used to determine whether the expression of a cellular marker is statistically different between two cell populations, suggesting candidates for new cellular phenotypes by providing an objective statistical measure. In addition, FlowMap-FR can indicate situations in which inappropriate splitting or merging of cell populations has occurred during gating procedures. We compared the FR statistic with the symmetric version of Kullback-Leibler divergence measure used in a previous population matching method with both simulated and real data. The FR statistic outperforms the symmetric version of KL-distance in distinguishing equivalent from nonequivalent cell
Hsiao, Chiaowen; Liu, Mengya; Stanton, Rick; McGee, Monnie; Qian, Yu
2015-01-01
Abstract Flow cytometry (FCM) is a fluorescence‐based single‐cell experimental technology that is routinely applied in biomedical research for identifying cellular biomarkers of normal physiological responses and abnormal disease states. While many computational methods have been developed that focus on identifying cell populations in individual FCM samples, very few have addressed how the identified cell populations can be matched across samples for comparative analysis. This article presents FlowMap‐FR, a novel method for cell population mapping across FCM samples. FlowMap‐FR is based on the Friedman–Rafsky nonparametric test statistic (FR statistic), which quantifies the equivalence of multivariate distributions. As applied to FCM data by FlowMap‐FR, the FR statistic objectively quantifies the similarity between cell populations based on the shapes, sizes, and positions of fluorescence data distributions in the multidimensional feature space. To test and evaluate the performance of FlowMap‐FR, we simulated the kinds of biological and technical sample variations that are commonly observed in FCM data. The results show that FlowMap‐FR is able to effectively identify equivalent cell populations between samples under scenarios of proportion differences and modest position shifts. As a statistical test, FlowMap‐FR can be used to determine whether the expression of a cellular marker is statistically different between two cell populations, suggesting candidates for new cellular phenotypes by providing an objective statistical measure. In addition, FlowMap‐FR can indicate situations in which inappropriate splitting or merging of cell populations has occurred during gating procedures. We compared the FR statistic with the symmetric version of Kullback–Leibler divergence measure used in a previous population matching method with both simulated and real data. The FR statistic outperforms the symmetric version of KL‐distance in distinguishing
NASA Astrophysics Data System (ADS)
Zhang, Youcai; Springel, Volker; Yang, Xiaohu
2010-10-01
We study the topology of cosmic large-scale structure through the genus statistics, using galaxy catalogs generated from the Millennium Simulation and observational data from the latest Sloan Digital Sky Survey Data Release (SDSS DR7). We introduce a new method for constructing galaxy density fields and for measuring the genus statistics of its isodensity surfaces. It is based on a Delaunay tessellation field estimation (DTFE) technique that allows the definition of a piece-wise continuous density field and the exact computation of the topology of its polygonal isodensity contours, without introducing any free numerical parameter. Besides this new approach, we also employ the traditional approaches of smoothing the galaxy distribution with a Gaussian of fixed width, or by adaptively smoothing with a kernel that encloses a constant number of neighboring galaxies. Our results show that the Delaunay-based method extracts the largest amount of topological information. Unlike the traditional approach for genus statistics, it is able to discriminate between the different theoretical galaxy catalogs analyzed here, both in real space and in redshift space, even though they are based on the same underlying simulation model. In particular, the DTFE approach detects with high confidence a discrepancy of one of the semi-analytic models studied here compared with the SDSS data, while the other models are found to be consistent.
Rivas-Ruiz, Rodolfo; Pérez-Rodríguez, Marcela; Talavera, Juan O
2013-01-01
Among the test to show differences between means, the Student t test is the most characteristic. Its basic algebraic structure shows the difference between two means weighted by their dispersion. In this way, you can estimate the p value and the 95 % confidence interval of the mean difference. An essential feature is that the variable from which the mean is going to be calculated must have a normal distribution. The Student t test is used to compare two unrelated means (compared between two maneuvers), this is known as t test for independent samples. It is also used to compare two related means (a comparison before and after a maneuver in just one group), what is called paired t test. When the comparison is between more than two means (three or more dependent means, or three or more independent means) an ANOVA test (or an analysis of variance) it is used to perform the analysis.
Cosmic statistics of statistics
NASA Astrophysics Data System (ADS)
Szapudi, István; Colombi, Stéphane; Bernardeau, Francis
1999-12-01
The errors on statistics measured in finite galaxy catalogues are exhaustively investigated. The theory of errors on factorial moments by Szapudi & Colombi is applied to cumulants via a series expansion method. All results are subsequently extended to the weakly non-linear regime. Together with previous investigations this yields an analytic theory of the errors for moments and connected moments of counts in cells from highly non-linear to weakly non-linear scales. For non-linear functions of unbiased estimators, such as the cumulants, the phenomenon of cosmic bias is identified and computed. Since it is subdued by the cosmic errors in the range of applicability of the theory, correction for it is inconsequential. In addition, the method of Colombi, Szapudi & Szalay concerning sampling effects is generalized, adapting the theory for inhomogeneous galaxy catalogues. While previous work focused on the variance only, the present article calculates the cross-correlations between moments and connected moments as well for a statistically complete description. The final analytic formulae representing the full theory are explicit but somewhat complicated. Therefore we have made available a fortran program capable of calculating the described quantities numerically (for further details e-mail SC at colombi@iap.fr). An important special case is the evaluation of the errors on the two-point correlation function, for which this should be more accurate than any method put forward previously. This tool will be immensely useful in the future for assessing the precision of measurements from existing catalogues, as well as aiding the design of new galaxy surveys. To illustrate the applicability of the results and to explore the numerical aspects of the theory qualitatively and quantitatively, the errors and cross-correlations are predicted under a wide range of assumptions for the future Sloan Digital Sky Survey. The principal results concerning the cumulants ξ, Q3 and Q4 is that
A Classroom Note on the "Spirit" of Statistics or the Effects of Self-Healing in Hypothesis Testing.
ERIC Educational Resources Information Center
Zirkel, Gene
1998-01-01
Discusses the effects on healing of attitude, positive thinking, and affirmations. Presents a mathematical example of hypothesis testing. Results point to the desirability of discussing such ideas with students to emphasize that the use of hypothesis testing is not simply a mechanical procedure. (ASK)
Durak, Sibel; Ercan, Eyup Sabri; Ardic, Ulku Akyol; Yuce, Deniz; Ercan, Elif; Ipci, Melis
2014-08-01
The aims of this study were to evaluate the neuropsychological characteristics of the restrictive (R) subtype according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition and the attention-deficit/hyperactivity disorder (ADHD) combined (CB) type and predominantly inattentive (PI) type subtypes and to evaluate whether methylphenidate (MPH) affects neurocognitive test battery scores according to these subtypes. This study included 360 children and adolescents (277 boys, 83 girls) between 7 and 15 years of age who had been diagnosed with ADHD and compared the neuropsychological characteristics and MPH treatment responses of patients with the R subtype-which has been suggested for inclusion among the ADHD subtypes in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-with those of patients with the PI and CB subtypes. They did not differ from the control subjects in the complex attention domain, which includes Continuous Performance Test, Stroop test, and Shifting Attention Test, which suggests that the R subtype displayed a lower level of deterioration in these domains compared with the PI and CB subtypes. The patients with the CB and PI subtypes did not differ from the control subjects in the Continuous Performance Test correct response domain, whereas those with the R subtype presented a poorer performance than the control subjects. The R subtype requires a more detailed evaluation because it presented similar results in the remaining neuropsychological evaluations and MPH responses.
Tempelman, R J
2004-01-01
Genetically modified (GM) corn hybrids have been recently compared against their isogenic reference counterparts in order to establish proof of safety as feedstuffs for dairy cattle. Most such studies have been based on the classical hypothesis test, whereby the null hypothesis is that of equivalence. Because the null hypothesis cannot be accepted, bioequivalence-testing procedures in which the alternative hypothesis is specified to be the equivalence hypothesis are proposed for these trials. Given a Type I error rate of 5%, this procedure is simply based on determining whether the 90% confidence interval on the GM vs. reference hybrid mean difference falls between two limits defining equivalence. Classical and bioequivalence power of test are determined for 4 x 4 Latin squares and double-reversal designs, the latter of which are ideally suited to bioequivalence studies. Although sufficient power likely exists for classical hypothesis testing in recent GM vs. reference hybrid studies, the same may not be true for bioequivalence testing depending on the equivalence limits chosen. The utility of observed or retrospective power to provide indirect evidence of bioequivalence is also criticized. Design and analysis issues pertain to Latin square and crossover studies in dairy nutrition studies are further reviewed. It is recommended that future studies should place greater emphasis on the use of confidence intervals relative to P-values to unify inference in both classical and bioequivalence-testing frameworks.
NASA Astrophysics Data System (ADS)
Woolley, Thomas W.; Dawson, George O.
It has been two decades since the first power analysis of a psychological journal and 10 years since the Journal of Research in Science Teaching made its contribution to this debate. One purpose of this article is to investigate what power-related changes, if any, have occurred in science education research over the past decade as a result of the earlier survey. In addition, previous recommendations are expanded and expounded upon within the context of more recent work in this area. The absence of any consistent mode of presenting statistical results, as well as little change with regard to power-related issues are reported. Guidelines for reporting the minimal amount of information demanded for clear and independent evaluation of research results by readers are also proposed.
Statistics 101 for Radiologists.
Anvari, Arash; Halpern, Elkan F; Samir, Anthony E
2015-10-01
Diagnostic tests have wide clinical applications, including screening, diagnosis, measuring treatment effect, and determining prognosis. Interpreting diagnostic test results requires an understanding of key statistical concepts used to evaluate test efficacy. This review explains descriptive statistics and discusses probability, including mutually exclusive and independent events and conditional probability. In the inferential statistics section, a statistical perspective on study design is provided, together with an explanation of how to select appropriate statistical tests. Key concepts in recruiting study samples are discussed, including representativeness and random sampling. Variable types are defined, including predictor, outcome, and covariate variables, and the relationship of these variables to one another. In the hypothesis testing section, we explain how to determine if observed differences between groups are likely to be due to chance. We explain type I and II errors, statistical significance, and study power, followed by an explanation of effect sizes and how confidence intervals can be used to generalize observed effect sizes to the larger population. Statistical tests are explained in four categories: t tests and analysis of variance, proportion analysis tests, nonparametric tests, and regression techniques. We discuss sensitivity, specificity, accuracy, receiver operating characteristic analysis, and likelihood ratios. Measures of reliability and agreement, including κ statistics, intraclass correlation coefficients, and Bland-Altman graphs and analysis, are introduced. PMID:26466186
Statistics 101 for Radiologists.
Anvari, Arash; Halpern, Elkan F; Samir, Anthony E
2015-10-01
Diagnostic tests have wide clinical applications, including screening, diagnosis, measuring treatment effect, and determining prognosis. Interpreting diagnostic test results requires an understanding of key statistical concepts used to evaluate test efficacy. This review explains descriptive statistics and discusses probability, including mutually exclusive and independent events and conditional probability. In the inferential statistics section, a statistical perspective on study design is provided, together with an explanation of how to select appropriate statistical tests. Key concepts in recruiting study samples are discussed, including representativeness and random sampling. Variable types are defined, including predictor, outcome, and covariate variables, and the relationship of these variables to one another. In the hypothesis testing section, we explain how to determine if observed differences between groups are likely to be due to chance. We explain type I and II errors, statistical significance, and study power, followed by an explanation of effect sizes and how confidence intervals can be used to generalize observed effect sizes to the larger population. Statistical tests are explained in four categories: t tests and analysis of variance, proportion analysis tests, nonparametric tests, and regression techniques. We discuss sensitivity, specificity, accuracy, receiver operating characteristic analysis, and likelihood ratios. Measures of reliability and agreement, including κ statistics, intraclass correlation coefficients, and Bland-Altman graphs and analysis, are introduced.
NASA Technical Reports Server (NTRS)
Feiveson, Alan H.; Ploutz-Snyder, Robert; Fiedler, James
2011-01-01
In their 2009 Annals of Statistics paper, Gavrilov, Benjamini, and Sarkar report the results of a simulation assessing the robustness of their adaptive step-down procedure (GBS) for controlling the false discovery rate (FDR) when normally distributed test statistics are serially correlated. In this study we extend the investigation to the case of multiple comparisons involving correlated non-central t-statistics, in particular when several treatments or time periods are being compared to a control in a repeated-measures design with many dependent outcome measures. In addition, we consider several dependence structures other than serial correlation and illustrate how the FDR depends on the interaction between effect size and the type of correlation structure as indexed by Foerstner s distance metric from an identity. The relationship between the correlation matrix R of the original dependent variables and R, the correlation matrix of associated t-statistics is also studied. In general R depends not only on R, but also on sample size and the signed effect sizes for the multiple comparisons.
Cap, J.S.
1997-11-01
Defining the maximum expected shock and vibration responses for an on-road truck transportation environment is strongly dependent on the amount of response data that can be obtained. One common test scheme consists of measuring response data over a relatively short prescribed road course and then reviewing that data to obtain the maximum response levels. The more mathematically rigorous alternative is to collect an unbiased ensemble of response data during a long road trip. This paper compares data gathered both ways during a recent on-road certification test for a tractor trailer van being designed by Sandia.
Velasco-Tapia, Fernando
2014-01-01
Magmatic processes have usually been identified and evaluated using qualitative or semiquantitative geochemical or isotopic tools based on a restricted number of variables. However, a more complete and quantitative view could be reached applying multivariate analysis, mass balance techniques, and statistical tests. As an example, in this work a statistical and quantitative scheme is applied to analyze the geochemical features for the Sierra de las Cruces (SC) volcanic range (Mexican Volcanic Belt). In this locality, the volcanic activity (3.7 to 0.5 Ma) was dominantly dacitic, but the presence of spheroidal andesitic enclaves and/or diverse disequilibrium features in majority of lavas confirms the operation of magma mixing/mingling. New discriminant-function-based multidimensional diagrams were used to discriminate tectonic setting. Statistical tests of discordancy and significance were applied to evaluate the influence of the subducting Cocos plate, which seems to be rather negligible for the SC magmas in relation to several major and trace elements. A cluster analysis following Ward's linkage rule was carried out to classify the SC volcanic rocks geochemical groups. Finally, two mass-balance schemes were applied for the quantitative evaluation of the proportion of the end-member components (dacitic and andesitic magmas) in the comingled lavas (binary mixtures). PMID:24737994
Velasco-Tapia, Fernando
2014-01-01
Magmatic processes have usually been identified and evaluated using qualitative or semiquantitative geochemical or isotopic tools based on a restricted number of variables. However, a more complete and quantitative view could be reached applying multivariate analysis, mass balance techniques, and statistical tests. As an example, in this work a statistical and quantitative scheme is applied to analyze the geochemical features for the Sierra de las Cruces (SC) volcanic range (Mexican Volcanic Belt). In this locality, the volcanic activity (3.7 to 0.5 Ma) was dominantly dacitic, but the presence of spheroidal andesitic enclaves and/or diverse disequilibrium features in majority of lavas confirms the operation of magma mixing/mingling. New discriminant-function-based multidimensional diagrams were used to discriminate tectonic setting. Statistical tests of discordancy and significance were applied to evaluate the influence of the subducting Cocos plate, which seems to be rather negligible for the SC magmas in relation to several major and trace elements. A cluster analysis following Ward's linkage rule was carried out to classify the SC volcanic rocks geochemical groups. Finally, two mass-balance schemes were applied for the quantitative evaluation of the proportion of the end-member components (dacitic and andesitic magmas) in the comingled lavas (binary mixtures). PMID:24737994
Velasco-Tapia, Fernando
2014-01-01
Magmatic processes have usually been identified and evaluated using qualitative or semiquantitative geochemical or isotopic tools based on a restricted number of variables. However, a more complete and quantitative view could be reached applying multivariate analysis, mass balance techniques, and statistical tests. As an example, in this work a statistical and quantitative scheme is applied to analyze the geochemical features for the Sierra de las Cruces (SC) volcanic range (Mexican Volcanic Belt). In this locality, the volcanic activity (3.7 to 0.5 Ma) was dominantly dacitic, but the presence of spheroidal andesitic enclaves and/or diverse disequilibrium features in majority of lavas confirms the operation of magma mixing/mingling. New discriminant-function-based multidimensional diagrams were used to discriminate tectonic setting. Statistical tests of discordancy and significance were applied to evaluate the influence of the subducting Cocos plate, which seems to be rather negligible for the SC magmas in relation to several major and trace elements. A cluster analysis following Ward's linkage rule was carried out to classify the SC volcanic rocks geochemical groups. Finally, two mass-balance schemes were applied for the quantitative evaluation of the proportion of the end-member components (dacitic and andesitic magmas) in the comingled lavas (binary mixtures).
Ramos Verri, Fellippo; Santiago Junior, Joel Ferreira; de Faria Almeida, Daniel Augusto; de Oliveira, Guilherme Bérgamo Brandão; de Souza Batista, Victor Eduardo; Marques Honório, Heitor; Noritomi, Pedro Yoshito; Pellizzer, Eduardo Piza
2015-01-01
The study of short implants is relevant to the biomechanics of dental implants, and research on crown increase has implications for the daily clinic. The aim of this study was to analyze the biomechanical interactions of a singular implant-supported prosthesis of different crown heights under vertical and oblique force, using the 3-D finite element method. Six 3-D models were designed with Invesalius 3.0, Rhinoceros 3D 4.0, and Solidworks 2010 software. Each model was constructed with a mandibular segment of bone block, including an implant supporting a screwed metal-ceramic crown. The crown height was set at 10, 12.5, and 15 mm. The applied force was 200 N (axial) and 100 N (oblique). We performed an ANOVA statistical test and Tukey tests; p<0.05 was considered statistically significant. The increase of crown height did not influence the stress distribution on screw prosthetic (p>0.05) under axial load. However, crown heights of 12.5 and 15 mm caused statistically significant damage to the stress distribution of screws and to the cortical bone (p<0.001) under oblique load. High crown to implant (C/I) ratio harmed microstrain distribution on bone tissue under axial and oblique loads (p<0.001). Crown increase was a possible deleterious factor to the screws and to the different regions of bone tissue.
NASA Astrophysics Data System (ADS)
Calderon, Christopher P.; Weiss, Lucien E.; Moerner, W. E.
2014-05-01
Experimental advances have improved the two- (2D) and three-dimensional (3D) spatial resolution that can be extracted from in vivo single-molecule measurements. This enables researchers to quantitatively infer the magnitude and directionality of forces experienced by biomolecules in their native environment. Situations where such force information is relevant range from mitosis to directed transport of protein cargo along cytoskeletal structures. Models commonly applied to quantify single-molecule dynamics assume that effective forces and velocity in the x ,y (or x ,y,z) directions are statistically independent, but this assumption is physically unrealistic in many situations. We present a hypothesis testing approach capable of determining if there is evidence of statistical dependence between positional coordinates in experimentally measured trajectories; if the hypothesis of independence between spatial coordinates is rejected, then a new model accounting for 2D (3D) interactions can and should be considered. Our hypothesis testing technique is robust, meaning it can detect interactions, even if the noise statistics are not well captured by the model. The approach is demonstrated on control simulations and on experimental data (directed transport of intraflagellar transport protein 88 homolog in the primary cilium).
Calderon, Christopher P; Weiss, Lucien E; Moerner, W E
2014-05-01
Experimental advances have improved the two- (2D) and three-dimensional (3D) spatial resolution that can be extracted from in vivo single-molecule measurements. This enables researchers to quantitatively infer the magnitude and directionality of forces experienced by biomolecules in their native environment. Situations where such force information is relevant range from mitosis to directed transport of protein cargo along cytoskeletal structures. Models commonly applied to quantify single-molecule dynamics assume that effective forces and velocity in the x,y (or x,y,z) directions are statistically independent, but this assumption is physically unrealistic in many situations. We present a hypothesis testing approach capable of determining if there is evidence of statistical dependence between positional coordinates in experimentally measured trajectories; if the hypothesis of independence between spatial coordinates is rejected, then a new model accounting for 2D (3D) interactions can and should be considered. Our hypothesis testing technique is robust, meaning it can detect interactions, even if the noise statistics are not well captured by the model. The approach is demonstrated on control simulations and on experimental data (directed transport of intraflagellar transport protein 88 homolog in the primary cilium). PMID:25353827
ERIC Educational Resources Information Center
Klein, Ariel; Badia, Toni
2015-01-01
In this study we show how complex creative relations can arise from fairly frequent semantic relations observed in everyday language. By doing this, we reflect on some key cognitive aspects of linguistic and general creativity. In our experimentation, we automated the process of solving a battery of Remote Associates Test tasks. By applying…
ERIC Educational Resources Information Center
Cheng, Ying-Yao; Wang, Wen-Chung; Ho, Yi-Hui
2009-01-01
Educational and psychological tests are often composed of multiple short subtests, each measuring a distinct latent trait. Unfortunately, short subtests suffer from low measurement precision, which makes the bandwidth-fidelity dilemma inevitable. In this study, the authors demonstrate how a multidimensional Rasch analysis can be employed to take…
Boareto, Marcelo; Caticha, Nestor
2014-01-01
Microarray data analysis typically consists in identifying a list of differentially expressed genes (DEG), i.e., the genes that are differentially expressed between two experimental conditions. Variance shrinkage methods have been considered a better choice than the standard t-test for selecting the DEG because they correct the dependence of the error with the expression level. This dependence is mainly caused by errors in background correction, which more severely affects genes with low expression values. Here, we propose a new method for identifying the DEG that overcomes this issue and does not require background correction or variance shrinkage. Unlike current methods, our methodology is easy to understand and implement. It consists of applying the standard t-test directly on the normalized intensity data, which is possible because the probe intensity is proportional to the gene expression level and because the t-test is scale- and location-invariant. This methodology considerably improves the sensitivity and robustness of the list of DEG when compared with the t-test applied to preprocessed data and to the most widely used shrinkage methods, Significance Analysis of Microarrays (SAM) and Linear Models for Microarray Data (LIMMA). Our approach is useful especially when the genes of interest have small differences in expression and therefore get ignored by standard variance shrinkage methods.
ERIC Educational Resources Information Center
Lange, Matthew; Dawson, Andrew
2009-01-01
To test claims that postcolonial civil violence is a common legacy of colonialism, we create a dataset on the colonial heritage of 160 countries and explore whether a history of colonialism is related to indicators of inter-communal conflict, political rebellion and civil war in the years 1960-1999. The analysis provides evidence against sweeping…
NASA Technical Reports Server (NTRS)
Alston, D. W.
1981-01-01
The considered research had the objective to design a statistical model that could perform an error analysis of curve fits of wind tunnel test data using analysis of variance and regression analysis techniques. Four related subproblems were defined, and by solving each of these a solution to the general research problem was obtained. The capabilities of the evolved true statistical model are considered. The least squares fit is used to determine the nature of the force, moment, and pressure data. The order of the curve fit is increased in order to delete the quadratic effect in the residuals. The analysis of variance is used to determine the magnitude and effect of the error factor associated with the experimental data.
NASA Astrophysics Data System (ADS)
Hilborn, Robert C.
2002-03-01
Using the q-deformed commutator formalism (``q mutators''), we have calculated the two-photon transition amplitude connecting a J=0 atomic ground state to a J=1 atomic excited state of the same parity. We find, in agreement with a semiclassical calculation, that this transition amplitude vanishes for two equal-frequency photons if the photons are traditional bosons with q=1. If q<1 (i.e., if the spin-statistics connection is violated for photons), then the amplitude is nonzero and is proportional to (1-q). Thus such an experiment, originally proposed by Budker and DeMille, provides a sensitive test of the spin-statistics connection for photons within the q-mutator formalism.
Zainal-Abideen, M; Aris, A; Yusof, F; Abdul-Majid, Z; Selamat, A; Omar, S I
2012-01-01
In this study of coagulation operation, a comparison was made between the optimum jar test values for pH, coagulant and coagulant aid obtained from traditional methods (an adjusted one-factor-at-a-time (OFAT) method) and with central composite design (the standard design of response surface methodology (RSM)). Alum (coagulant) and polymer (coagulant aid) were used to treat a water source with very low pH and high aluminium concentration at Sri-Gading water treatment plant (WTP) Malaysia. The optimum conditions for these factors were chosen when the final turbidity, pH after coagulation and residual aluminium were within 0-5 NTU, 6.5-7.5 and 0-0.20 mg/l respectively. Traditional and RSM jar tests were conducted to find their respective optimum coagulation conditions. It was observed that the optimum dose for alum obtained through the traditional method was 12 mg/l, while the value for polymer was set constant at 0.020 mg/l. Through RSM optimization, the optimum dose for alum was 7 mg/l and for polymer was 0.004 mg/l. Optimum pH for the coagulation operation obtained through traditional methods and RSM was 7.6. The final turbidity, pH after coagulation and residual aluminium recorded were all within acceptable limits. The RSM method was demonstrated to be an appropriate approach for the optimization and was validated by a further test.
NASA Astrophysics Data System (ADS)
Markowitz, A.
2015-09-01
We summarize two papers providing the first X-ray-derived statistical constraints for both clumpy-torus model parameters and cloud ensemble properties. In Markowitz, Krumpe, & Nikutta (2014), we explored multi-timescale variability in line-of-sight X-ray absorbing gas as a function of optical classification. We examined 55 Seyferts monitored with the Rossi X-ray Timing Explorer, and found in 8 objects a total of 12 eclipses, with durations between hours and years. Most clouds are commensurate with the outer portions of the BLR, or the inner regions of infrared-emitting dusty tori. The detection of eclipses in type Is disfavors sharp-edged tori. We provide probabilities to observe a source undergoing an absorption event for both type Is and IIs, yielding constraints in [N_0, sigma, i] parameter space. In Nikutta et al., in prep., we infer that the small cloud angular sizes, as seen from the SMBH, imply the presence of >10^7 clouds in BLR+torus to explain observed covering factors. Cloud size is roughly proportional to distance from the SMBH, hinting at the formation processes (e.g. disk fragmentation). All observed clouds are sub-critical with respect to tidal disruption; self-gravity alone cannot contain them. External forces (e.g. magnetic fields, ambient pressure) are needed to contain them, or otherwise the clouds must be short-lived. Finally, we infer that the radial cloud density distribution behaves as 1/r^{0.7}, compatible with VLTI observations. Our results span both dusty and non-dusty clumpy media, and probe model parameter space complementary to that for short-term eclipses observed with XMM-Newton, Suzaku, and Chandra.
Paybins, Katherine S.; Nishikawa, Tracy; Izbicki, John A.; Reichard, Eric G.
1998-01-01
To better understand flow processes, solute-transport processes, and ground-water/surface-water interactions on the Santa Clara River in Ventura County, California, a 24-hour fluorescent-dye tracer study was performed under steady-state flow conditions on a 28-mile reach of the river. The study reach includes perennial (uppermost and lowermost) subreaches and ephemeral subreaches of the lower Piru Creek and the middle Santa Clara River. Dye was injected at a site on Piru Creek, and fluorescence of river water was measured continuously at four sites and intermittently at two sites. Discharge measurements were also made at the six sites. The time of travel of the dye, peak dye concentration, and time-variance of time-concentration curves were obtained at each site. The long tails of the time-concentration curves are indicative of sources/sinks within the river, such as riffles and pools, or transient bank storage. A statistical analysis of the data indicates that, in general, the transport characteristics follow Fickian theory. These data and previously collected discharge data were used to calibrate a one-dimensional flow model (DAFLOW) and a solute-transport model (BLTM). DAFLOW solves a simplified form of the diffusion-wave equation and uses empirical relations between flow rate and cross-sectional area, and flow rate and channel width. BLTM uses the velocity data from DAFLOW and solves the advection-dispersion transport equation, including first-order decay. The simulations of dye transport indicated that (1) ground-water recharge explains the loss of dye mass in the middle, ephemeral, subreaches, and (2) ground-water recharge does not explain the loss of dye mass in the uppermost and lowermost, perennial, subreaches. This loss of mass was simulated using a linear decay term. The loss of mass in the perennial subreaches may be caused by a combination of photodecay or adsorption/desorption.
Ronco, A; Gagnon, P; Diaz-Baez, M C; Arkhipchuk, V; Castillo, G; Castillo, L E; Dutka, B J; Pica-Granados, Y; Ridal, J; Srivastava, R C; Sánchez, A
2002-01-01
There is an urgent need to evaluate the presence of toxicants in waters used for human consumption and to develop strategies to reduce and prevent their contamination. The International Development Research Centre undertook an intercalibration project to develop and validate a battery of bioassays for toxicity testing of water samples. The project was carried out in two phases by research institutions from eight countries that formed the WaterTox network. Results for the first phase were reported in the special September 2000 issue of Environmental Toxicology. Phase II involved toxicity screening tests of environmental and blind samples (chemical solutions of unknown composition to participating laboratories) using the following battery: Daphnia magna, Hydra attenuata, seed root inhibition with Lactuca sativa, and Selenastrum capricornutum. This battery was also used to assess potential toxicity in concentrated (10x) water samples. Results are presented for a set of six blind samples sent to the participating laboratories over a 1-year period. Analyses were performed for each bioassay to evaluate variations among laboratories of responses to negative controls, violations of test quality control criteria, false positive responses induced by sample concentration, and variability within and between labs of responses to toxic samples. Analyses of the data from all bioassays and labs provided comparisons of false positive rates (based on blind negative samples), test sensitivities to a metal or organic toxicant, and interlaboratory test variability. Results indicate that the battery was reliable in detecting toxicity when present. However, some false positives were identified with a concentrated soft-water sample and with the Lactuca and Hydra (sublethal end-point) tests. Probabilities of detecting false positives for individual and combined toxic responses of the four bioassays are presented. Overall, interlaboratory comparisons indicate a good reliability of the
NASA Astrophysics Data System (ADS)
Brazhnik, Olga D.; Freed, Karl F.
1996-07-01
The lattice cluster theory (LCT) is extended to enable inclusion of longer range correlation contributions to the partition function of lattice model polymers in the athermal limit. A diagrammatic technique represents the expansion of the partition function in powers of the inverse lattice coordination number. Graph theory is applied to sort, classify, and evaluate the numerous diagrams appearing in higher orders. New general theorems are proven that provide a significant reduction in the computational labor required to evaluate the contributions from higher order correlations. The new algorithm efficiently generates the correction to the Flory mean field approximation from as many as eight sterically interacting bonds. While the new results contain the essential ingredients for treating a system of flexible chains with arbitrary lengths and concentrations, the complexity of our new algorithm motivates us to test the theory here for the simplest case of a system of lattice dimers by comparison to the dimer packing entropies from the work of Gaunt. This comparison demonstrates that the eight bond LCT is exact through order φ5 for dimers in one through three dimensions, where φ is the volume fraction of dimers. A subsequent work will use the contracted diagrams, derived and tested here, to treat the packing entropy for a system of flexible N-mers at a volume fraction of φ on hypercubic lattices.
NASA Astrophysics Data System (ADS)
Markowitz, Alex; Krumpe, Mirko; Nikutta, R.
2016-06-01
In two papers (Markowitz, Krumpe, & Nikutta 2014, and Nikutta et al., in prep.), we derive the first X-ray statistical constraints for clumpy-torus models in Seyfert AGN by quantifying multi-timescale variability in line of-sight X-ray absorbing gas as a function of optical classification.We systematically search for discrete absorption events in the vast archive of RXTE monitoring of 55 nearby type Is and Compton-thin type IIs. We are sensitive to discrete absorption events due to clouds of full-covering, neutral/mildly ionized gas transiting the line of sight. Our results apply to both dusty and non-dusty clumpy media, and probe model parameter space complementary to that for eclipses observed with XMM-Newton, Suzaku, and Chandra.We detect twelve eclipse events in eight Seyferts, roughly tripling the number previously published from this archive. Event durations span hours to years. Most of our detected clouds are Compton-thin, and most clouds' distances from the black hole are inferred to be commensurate with the outer portions of the BLR or the inner regions of infrared-emitting dusty tori.We present the density profiles of the highest-quality eclipse events; the column density profile for an eclipsing cloud in NGC 3783 is doubly spiked, possibly indicating a cloud that is being tidallysheared. We discuss implications for cloud distributions in the context of clumpy-torus models. We calculate eclipse probabilities for orientation-dependent Type I/II unification schemes.We present constraints on cloud sizes, stability, and radial distribution. We infer that clouds' small angular sizes as seen from the SMBH imply 107 clouds required across the BLR + torus. Cloud size is roughly proportional to distance from the black hole, hinting at the formation processes (e.g., disk fragmentation). All observed clouds are sub-critical with respect to tidal disruption; self-gravity alone cannot contain them. External forces, such as magnetic fields or ambient pressure, are
Dziak, John J.; Lanza, Stephanie T.; Tan, Xianming
2014-01-01
Selecting the number of different classes which will be assumed to exist in the population is an important step in latent class analysis (LCA). The bootstrap likelihood ratio test (BLRT) provides a data-driven way to evaluate the relative adequacy of a (K −1)-class model compared to a K-class model. However, very little is known about how to predict the power or the required sample size for the BLRT in LCA. Based on extensive Monte Carlo simulations, we provide practical effect size measures and power curves which can be used to predict power for the BLRT in LCA given a proposed sample size and a set of hypothesized population parameters. Estimated power curves and tables provide guidance for researchers wishing to size a study to have sufficient power to detect hypothesized underlying latent classes. PMID:25328371
NASA Astrophysics Data System (ADS)
Lee, Lopaka; Helsel, Dennis
2007-05-01
Analysis of low concentrations of trace contaminants in environmental media often results in left-censored data that are below some limit of analytical precision. Interpretation of values becomes complicated when there are multiple detection limits in the data—perhaps as a result of changing analytical precision over time. Parametric and semi-parametric methods, such as maximum likelihood estimation and robust regression on order statistics, can be employed to model distributions of multiply censored data and provide estimates of summary statistics. However, these methods are based on assumptions about the underlying distribution of data. Nonparametric methods provide an alternative that does not require such assumptions. A standard nonparametric method for estimating summary statistics of multiply-censored data is the Kaplan-Meier (K-M) method. This method has seen widespread usage in the medical sciences within a general framework termed "survival analysis" where it is employed with right-censored time-to-failure data. However, K-M methods are equally valid for the left-censored data common in the geosciences. Our S-language software provides an analytical framework based on K-M methods that is tailored to the needs of the earth and environmental sciences community. This includes routines for the generation of empirical cumulative distribution functions, prediction or exceedance probabilities, and related confidence limits computation. Additionally, our software contains K-M-based routines for nonparametric hypothesis testing among an unlimited number of grouping variables. A primary characteristic of K-M methods is that they do not perform extrapolation and interpolation. Thus, these routines cannot be used to model statistics beyond the observed data range or when linear interpolation is desired. For such applications, the aforementioned parametric and semi-parametric methods must be used.
Lee, L.; Helsel, D.
2007-01-01
Analysis of low concentrations of trace contaminants in environmental media often results in left-censored data that are below some limit of analytical precision. Interpretation of values becomes complicated when there are multiple detection limits in the data-perhaps as a result of changing analytical precision over time. Parametric and semi-parametric methods, such as maximum likelihood estimation and robust regression on order statistics, can be employed to model distributions of multiply censored data and provide estimates of summary statistics. However, these methods are based on assumptions about the underlying distribution of data. Nonparametric methods provide an alternative that does not require such assumptions. A standard nonparametric method for estimating summary statistics of multiply-censored data is the Kaplan-Meier (K-M) method. This method has seen widespread usage in the medical sciences within a general framework termed "survival analysis" where it is employed with right-censored time-to-failure data. However, K-M methods are equally valid for the left-censored data common in the geosciences. Our S-language software provides an analytical framework based on K-M methods that is tailored to the needs of the earth and environmental sciences community. This includes routines for the generation of empirical cumulative distribution functions, prediction or exceedance probabilities, and related confidence limits computation. Additionally, our software contains K-M-based routines for nonparametric hypothesis testing among an unlimited number of grouping variables. A primary characteristic of K-M methods is that they do not perform extrapolation and interpolation. Thus, these routines cannot be used to model statistics beyond the observed data range or when linear interpolation is desired. For such applications, the aforementioned parametric and semi-parametric methods must be used.
Explorations in statistics: statistical facets of reproducibility.
Curran-Everett, Douglas
2016-06-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This eleventh installment of Explorations in Statistics explores statistical facets of reproducibility. If we obtain an experimental result that is scientifically meaningful and statistically unusual, we would like to know that our result reflects a general biological phenomenon that another researcher could reproduce if (s)he repeated our experiment. But more often than not, we may learn this researcher cannot replicate our result. The National Institutes of Health and the Federation of American Societies for Experimental Biology have created training modules and outlined strategies to help improve the reproducibility of research. These particular approaches are necessary, but they are not sufficient. The principles of hypothesis testing and estimation are inherent to the notion of reproducibility in science. If we want to improve the reproducibility of our research, then we need to rethink how we apply fundamental concepts of statistics to our science.
Smith, Alwyn
1969-01-01
This paper is based on an analysis of questionnaires sent to the health ministries of Member States of WHO asking for information about the extent, nature, and scope of morbidity statistical information. It is clear that most countries collect some statistics of morbidity and many countries collect extensive data. However, few countries relate their collection to the needs of health administrators for information, and many countries collect statistics principally for publication in annual volumes which may appear anything up to 3 years after the year to which they refer. The desiderata of morbidity statistics may be summarized as reliability, representativeness, and relevance to current health problems. PMID:5306722
Statistical Inference at Work: Statistical Process Control as an Example
ERIC Educational Resources Information Center
Bakker, Arthur; Kent, Phillip; Derry, Jan; Noss, Richard; Hoyles, Celia
2008-01-01
To characterise statistical inference in the workplace this paper compares a prototypical type of statistical inference at work, statistical process control (SPC), with a type of statistical inference that is better known in educational settings, hypothesis testing. Although there are some similarities between the reasoning structure involved in…
Explorations in Statistics: Power
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2010-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This fifth installment of "Explorations in Statistics" revisits power, a concept fundamental to the test of a null hypothesis. Power is the probability that we reject the null hypothesis when it is false. Four things affect…
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2012-01-01
The term "data snooping" refers to the practice of choosing which statistical analyses to apply to a set of data after having first looked at those data. Data snooping contradicts a fundamental precept of applied statistics, that the scheme of analysis is to be planned in advance. In this column, the authors shall elucidate the statistical…
NSTec Environmental Restoration
2009-04-20
A statistical analysis and geologic evaluation of recently acquired laboratory-derived physical property data are being performed to better understand and more precisely correlate physical properties with specific geologic parameters associated with non-zeolitized tuffs at the Nevada Test Site. Physical property data include wet and dry bulk density, grain density (i.e., specific gravity), total porosity, and effective porosity. Geologic parameters utilized include degree of welding, lithology, stratigraphy, geographic area, and matrix mineralogy (i.e., vitric versus devitrified). Initial results indicate a very good correlation between physical properties and geologic parameters such as degree of welding, lithology, and matrix mineralogy. However, physical properties appear to be independent of stratigraphy and geographic area, suggesting that the data are transferrable with regards to these two geologic parameters. Statistical analyses also indicate that the assumed grain density of 2.65 grams per cubic centimeter used to calculate porosity in some samples is too high. This results in corresponding calculated porosity values approximately 5 percent too high (e.g., 45 percent versus 40 percent), which can be significant in the lower porosity rocks. Similar analyses and evaluations of zeolitic tuffs and carbonate rock physical properties data are ongoing as well as comparisons to geophysical log values.
Price-Whelan, Adrian M.; Agüeros, Marcel A.; Fournier, Amanda P.; Street, Rachel; Ofek, Eran O.; Covey, Kevin R.; Levitan, David; Sesar, Branimir; Laher, Russ R.; Surace, Jason
2014-01-20
Many photometric time-domain surveys are driven by specific goals, such as searches for supernovae or transiting exoplanets, which set the cadence with which fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several sub-surveys are conducted in parallel, leading to non-uniform sampling over its ∼20,000 deg{sup 2} footprint. While the median 7.26 deg{sup 2} PTF field has been imaged ∼40 times in the R band, ∼2300 deg{sup 2} have been observed >100 times. We use PTF data to study the trade off between searching for microlensing events in a survey whose footprint is much larger than that of typical microlensing searches, but with far-from-optimal time sampling. To examine the probability that microlensing events can be recovered in these data, we test statistics used on uniformly sampled data to identify variables and transients. We find that the von Neumann ratio performs best for identifying simulated microlensing events in our data. We develop a selection method using this statistic and apply it to data from fields with >10 R-band observations, 1.1 × 10{sup 9} light curves, uncovering three candidate microlensing events. We lack simultaneous, multi-color photometry to confirm these as microlensing events. However, their number is consistent with predictions for the event rate in the PTF footprint over the survey's three years of operations, as estimated from near-field microlensing models. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large data sets, which will be useful to future time-domain surveys, such as that planned with the Large Synoptic Survey Telescope.
NASA Astrophysics Data System (ADS)
Price-Whelan, Adrian M.; Agüeros, Marcel A.; Fournier, Amanda P.; Street, Rachel; Ofek, Eran O.; Covey, Kevin R.; Levitan, David; Laher, Russ R.; Sesar, Branimir; Surace, Jason
2014-01-01
Many photometric time-domain surveys are driven by specific goals, such as searches for supernovae or transiting exoplanets, which set the cadence with which fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several sub-surveys are conducted in parallel, leading to non-uniform sampling over its ~20,000 deg2 footprint. While the median 7.26 deg2 PTF field has been imaged ~40 times in the R band, ~2300 deg2 have been observed >100 times. We use PTF data to study the trade off between searching for microlensing events in a survey whose footprint is much larger than that of typical microlensing searches, but with far-from-optimal time sampling. To examine the probability that microlensing events can be recovered in these data, we test statistics used on uniformly sampled data to identify variables and transients. We find that the von Neumann ratio performs best for identifying simulated microlensing events in our data. We develop a selection method using this statistic and apply it to data from fields with >10 R-band observations, 1.1 × 109 light curves, uncovering three candidate microlensing events. We lack simultaneous, multi-color photometry to confirm these as microlensing events. However, their number is consistent with predictions for the event rate in the PTF footprint over the survey's three years of operations, as estimated from near-field microlensing models. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large data sets, which will be useful to future time-domain surveys, such as that planned with the Large Synoptic Survey Telescope.
Pan, Deyun; Sun, Ning; Cheung, Kei-Hoi; Guan, Zhong; Ma, Ligeng; Holford, Matthew; Deng, Xingwang; Zhao, Hongyu
2003-01-01
Background To date, many genomic and pathway-related tools and databases have been developed to analyze microarray data. In published web-based applications to date, however, complex pathways have been displayed with static image files that may not be up-to-date or are time-consuming to rebuild. In addition, gene expression analyses focus on individual probes and genes with little or no consideration of pathways. These approaches reveal little information about pathways that are key to a full understanding of the building blocks of biological systems. Therefore, there is a need to provide useful tools that can generate pathways without manually building images and allow gene expression data to be integrated and analyzed at pathway levels for such experimental organisms as Arabidopsis. Results We have developed PathMAPA, a web-based application written in Java that can be easily accessed over the Internet. An Oracle database is used to store, query, and manipulate the large amounts of data that are involved. PathMAPA allows its users to (i) upload and populate microarray data into a database; (ii) integrate gene expression with enzymes of the pathways; (iii) generate pathway diagrams without building image files manually; (iv) visualize gene expressions for each pathway at enzyme, locus, and probe levels; and (v) perform statistical tests at pathway, enzyme and gene levels. PathMAPA can be used to examine Arabidopsis thaliana gene expression patterns associated with metabolic pathways. Conclusion PathMAPA provides two unique features for the gene expression analysis of Arabidopsis thaliana: (i) automatic generation of pathways associated with gene expression and (ii) statistical tests at pathway level. The first feature allows for the periodical updating of genomic data for pathways, while the second feature can provide insight into how treatments affect relevant pathways for the selected experiment(s). PMID:14604444
Winters, Ryan; Winters, Andrew; Amedee, Ronald G.
2010-01-01
The Accreditation Council for Graduate Medical Education sets forth a number of required educational topics that must be addressed in residency and fellowship programs. We sought to provide a primer on some of the important basic statistical concepts to consider when examining the medical literature. It is not essential to understand the exact workings and methodology of every statistical test encountered, but it is necessary to understand selected concepts such as parametric and nonparametric tests, correlation, and numerical versus categorical data. This working knowledge will allow you to spot obvious irregularities in statistical analyses that you encounter. PMID:21603381
The Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute works to provide information on cancer statistics in an effort to reduce the burden of cancer among the U.S. population.
... cancer statistics across the world. U.S. Cancer Mortality Trends The best indicator of progress against cancer is ... the number of cancer survivors has increased. These trends show that progress is being made against the ...
Streiner, David L
2015-10-01
Testing many null hypotheses in a single study results in an increased probability of detecting a significant finding just by chance (the problem of multiplicity). Debates have raged over many years with regard to whether to correct for multiplicity and, if so, how it should be done. This article first discusses how multiple tests lead to an inflation of the α level, then explores the following different contexts in which multiplicity arises: testing for baseline differences in various types of studies, having >1 outcome variable, conducting statistical tests that produce >1 P value, taking multiple "peeks" at the data, and unplanned, post hoc analyses (i.e., "data dredging," "fishing expeditions," or "P-hacking"). It then discusses some of the methods that have been proposed for correcting for multiplicity, including single-step procedures (e.g., Bonferroni); multistep procedures, such as those of Holm, Hochberg, and Šidák; false discovery rate control; and resampling approaches. Note that these various approaches describe different aspects and are not necessarily mutually exclusive. For example, resampling methods could be used to control the false discovery rate or the family-wise error rate (as defined later in this article). However, the use of one of these approaches presupposes that we should correct for multiplicity, which is not universally accepted, and the article presents the arguments for and against such "correction." The final section brings together these threads and presents suggestions with regard to when it makes sense to apply the corrections and how to do so. PMID:26245806
NASA Astrophysics Data System (ADS)
Hermann, Claudine
Statistical Physics bridges the properties of a macroscopic system and the microscopic behavior of its constituting particles, otherwise impossible due to the giant magnitude of Avogadro's number. Numerous systems of today's key technologies - such as semiconductors or lasers - are macroscopic quantum objects; only statistical physics allows for understanding their fundamentals. Therefore, this graduate text also focuses on particular applications such as the properties of electrons in solids with applications, and radiation thermodynamics and the greenhouse effect.
Osnes, J.D. ); Winberg, A.; Andersson, J.E.; Larsson, N.A. )
1991-09-27
Statistical and probabilistic methods for estimating the probability that a fracture is nonconductive (or equivalently, the conductive-fracture frequency) and the distribution of the transmissivities of conductive fractures from transmissivity measurements made in single-hole injection (well) tests were developed. These methods were applied to a database consisting of over 1,000 measurements made in nearly 25 km of borehole at five sites in Sweden. The depths of the measurements ranged from near the surface to over 600-m deep, and packer spacings of 20- and 25-m were used. A probabilistic model that describes the distribution of a series of transmissivity measurements was derived. When the parameters of this model were estimated using maximum likelihood estimators, the resulting estimated distributions generally fit the cumulative histograms of the transmissivity measurements very well. Further, estimates of the mean transmissivity of conductive fractures based on the maximum likelihood estimates of the model's parameters were reasonable, both in magnitude and in trend, with respect to depth. The estimates of the conductive fracture probability were generated in the range of 0.5--5.0 percent, with the higher values at shallow depths and with increasingly smaller values as depth increased. An estimation procedure based on the probabilistic model and the maximum likelihood estimators of its parameters was recommended. Some guidelines regarding the design of injection test programs were drawn from the recommended estimation procedure and the parameter estimates based on the Swedish data. 24 refs., 12 figs., 14 tabs.
Schulpen, Sjors H W; Pennings, Jeroen L A; Tonk, Elisa C M; Piersma, Aldert H
2014-03-21
The embryonic stem cell test (EST) is applied as a model system for detection of embryotoxicants. The application of transcriptomics allows a more detailed effect assessment compared to the morphological endpoint. Genes involved in cell differentiation, modulated by chemical exposures, may be useful as biomarkers of developmental toxicity. We describe a statistical approach to obtain a predictive gene set for toxicity potency ranking of compounds within one class. This resulted in a gene set based on differential gene expression across concentration-response series of phthalatic monoesters. We determined the concentration at which gene expression was changed at least 1.5-fold. Genes responding with the same potency ranking in vitro and in vivo embryotoxicity were selected. A leave-one-out cross-validation showed that the relative potency of each phthalate was always predicted correctly. The classical morphological 50% effect level (ID50) in EST was similar to the predicted concentration using gene set expression responses. A general down-regulation of development-related genes and up-regulation of cell-cycle related genes was observed, reminiscent of the differentiation inhibition in EST. This study illustrates the feasibility of applying dedicated gene set selections as biomarkers for developmental toxicity potency ranking on the basis of in vitro testing in the EST.
Cason, J A; Cox, N A; Buhr, R J; Richardson, L J
2010-09-01
Whether a required Salmonella test series is passed or failed depends not only on the presence of the bacteria but also on the methods for taking samples, the methods for culturing samples, and the statistics associated with the sampling plan. The pass-fail probabilities of the 2-class attribute sampling plans used for testing chilled chicken carcasses in the United States and Europe were compared by calculation and simulation. Testing in the United States uses whole-carcass rinses (WCR), with a maximum number of 12 positives out of 51 carcasses in a test set. Those numbers were chosen so that a plant operating with a Salmonella prevalence of 20%, the national baseline result for broiler chicken carcasses, has an approximately 80% probability of passing a test set. The European Union requires taking neck skin samples of approximately 8.3 g each from 150 carcasses, with the neck skins cultured in pools of 3 and with 7 positives as the maximum passing score for a test set of 50 composite samples. For each of these sampling plans, binomial probabilities were calculated and 100,000 complete sampling sets were simulated using a random number generator in a spreadsheet. Calculations indicated that a 20% positive rate in WCR samples was approximately equivalent to an 11.42% positive rate in composite neck skin samples or a 3.96% positive rate in individual neck skin samples within a pool of 3. With 20% as the prevalence rate, 79.3% of the simulated WCR sets passed with 12 or fewer positive carcasses per set, very near the expected 80% rate. Under simulated European conditions, a Salmonella prevalence of 3.96% in individual neck skin samples yielded a passing rate of 79.1%. The 2 sampling plans thus have roughly equivalent outcomes if WCR samples have a Salmonella-positive rate of 20% and individual neck skin samples have a positive rate of 3.96%. Sampling and culturing methods must also be considered in comparing the different standards for Salmonella.
Fox, K
2007-06-12
The Savannah River National Laboratory (SRNL) is part of a consortium that is looking to improve the retention of aluminum, chromium, and sulfate in high level radioactive waste (HLW) glass. Such glass has been produced by the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS) in South Carolina since it began operating in 1996 and is planned to be produced by the River Protection Project-Waste Treatment Plant (WTP) at the Hanford Site in Washington. The consortium conducting this study, which is designated as Task No.6 by the Department of Energy (DOE) Environmental Management (EM) program sponsoring this effort, is made up of personnel from SRNL, the Pacific Northwest National Laboratory (PNNL), and the V.G. Khlopin Radium Institute (KRI). Coordinated glass experimental work will be performed by each member of the consortium. The glasses that are being studied were selected to further the understanding of composition-property relationships within the glass regions of interest to both DWPF and WTP. Forty-five (45) glasses, making up the US test matrix, were batched and fabricated to support the study. The chemical compositions of these glasses were measured by SRNL's Process Science Analytical Laboratory (PSAL) under the auspices of an analytical plan. In addition, two heat treatments (quenched and centerline canister cooled, ccc) of each glass were subjected to the 7-day Product Consistency Test (PCT) to assess their durabilities. More specifically, the Method A of the PCT (ASTM C-1285-2002) was used for these tests. Measurements of the resulting leachate solutions were conducted by PSAL under the auspices of three analytical plans. A statistical review of the PSAL measurements of the chemical compositions and of the PCT results for the glasses making up the US test matrix is provided in this memorandum. Target, measured, and measured bias-corrected compositional views were determined for these glasses. The durability results for the US
ERIC Educational Resources Information Center
Anderson, Paul S.; Hyers, Albert D.
Three descriptive statistics (difficulty, discrimination, and reliability) of multiple-choice (MC) test items were compared to those of a new (1980s) format of machine-scored questions. The new method, answer-bank multi-digit testing (MDT), uses alphabetized lists of up to 1,000 alternatives and approximates the completion style of assessment…
Ren, Xuemei; Yang, Shitong; Hu, Fengchun; He, Bo; Xu, Jinzhang; Tan, Xiaoli; Wang, Xiangke
2013-05-15
Extended X-ray absorption fine structure (EXAFS) spectroscopy combined with statistical F-tests is used to investigate the local atomic structures of Ni(II) adsorbed on Na-rectorite. The EXAFS analysis results of Ni(II) sorption samples indicate that the first coordination shell consists of ~6 O at the Ni-O interatomic distance (R) of ~2.04 Å. The presence of Ni backscattering at R(Ni-Ni) = 3.06 Å in the second coordination shell suggests the formation of Ni(II) precipitate. The results of F-tests show that the Ni(II) precipitate is Ni-Al layered double hydroxide (LDH). Our results demonstrate that Ni(II) ions are retained via different mechanisms depending on solution conditions. At low pH, Ni retention is controlled mainly by the outer-sphere surface complexation. With increasing pH, outer-sphere and inner-sphere surface complexation dominate Ni uptake. Furthermore, Ni surface loading increases with temperature increasing at pH 6.5 due to the formation of inner-sphere surface complexes and Ni-Al LDH. The formation of Ni-Al LDH becomes the dominate mechanism at the elevated pH and temperature. In the presence of humic substances, the sorption of Ni(II) on Na-rectorite is dominated by the formation of ternary surface complexes. These results are important to understand the physicochemical behavior of Ni(II) in the natural environment. PMID:23500786
NASA Astrophysics Data System (ADS)
Lauter, Judith L.; Ninness, Chris
2003-10-01
The Auditory Cross-Section (AXS) Test Battery [J. L. Lauter, Behav. Res. Methods Instrum. Comput. 32, 180-190 (2000)], described in presentations to ASA in 2002 and 2003, is designed to document dynamic relations linking the cortex, brainstem, and body periphery (whether physics, physiology, or behavior) on an individually-specific basis. Data collections using the battery typically employ a within-subject, time-varying, multivariate design, yet conventional group statistics do not provide satisfactory means of treating such data. We have recently developed an approach based on Kohonens (2001) Self-Organizing Maps (SOM) algorithm, which categorizes time-varying profiles across variables, either within- or between-subjects. The treatment entails three steps: (1) z-score transformation of all raw data; (2) employing the SOM to sort the time-varying profiles into groups; and (3) deriving an estimate of the bounds for the Bayes error rate. Our three-step procedure will be briefly described and illustrated with data from a recent study combining otoacoustic emissions, auditory brainstem responses, and cortical qEEG.
Du, Pan; Feng, Gang; Flatow, Jared; Song, Jie; Holko, Michelle; Kibbe, Warren A; Lin, Simon M
2009-06-15
Subjective methods have been reported to adapt a general-purpose ontology for a specific application. For example, Gene Ontology (GO) Slim was created from GO to generate a highly aggregated report of the human-genome annotation. We propose statistical methods to adapt the general purpose, OBO Foundry Disease Ontology (DO) for the identification of gene-disease associations. Thus, we need a simplified definition of disease categories derived from implicated genes. On the basis of the assumption that the DO terms having similar associated genes are closely related, we group the DO terms based on the similarity of gene-to-DO mapping profiles. Two types of binary distance metrics are defined to measure the overall and subset similarity between DO terms. A compactness-scalable fuzzy clustering method is then applied to group similar DO terms. To reduce false clustering, the semantic similarities between DO terms are also used to constrain clustering results. As such, the DO terms are aggregated and the redundant DO terms are largely removed. Using these methods, we constructed a simplified vocabulary list from the DO called Disease Ontology Lite (DOLite). We demonstrated that DOLite results in more interpretable results than DO for gene-disease association tests. The resultant DOLite has been used in the Functional Disease Ontology (FunDO) Web application at http://www.projects.bioinformatics.northwestern.edu/fundo.
NASA Technical Reports Server (NTRS)
Young, M.; Koslovsky, M.; Schaefer, Caroline M.; Feiveson, A. H.
2017-01-01
Back by popular demand, the JSC Biostatistics Laboratory and LSAH statisticians are offering an opportunity to discuss your statistical challenges and needs. Take the opportunity to meet the individuals offering expert statistical support to the JSC community. Join us for an informal conversation about any questions you may have encountered with issues of experimental design, analysis, or data visualization. Get answers to common questions about sample size, repeated measures, statistical assumptions, missing data, multiple testing, time-to-event data, and when to trust the results of your analyses.
Croarkin, M. Carroll
2001-01-01
For more than 50 years, the Statistical Engineering Division (SED) has been instrumental in the success of a broad spectrum of metrology projects at NBS/NIST. This paper highlights fundamental contributions of NBS/NIST statisticians to statistics and to measurement science and technology. Published methods developed by SED staff, especially during the early years, endure as cornerstones of statistics not only in metrology and standards applications, but as data-analytic resources used across all disciplines. The history of statistics at NBS/NIST began with the formation of what is now the SED. Examples from the first five decades of the SED illustrate the critical role of the division in the successful resolution of a few of the highly visible, and sometimes controversial, statistical studies of national importance. A review of the history of major early publications of the division on statistical methods, design of experiments, and error analysis and uncertainty is followed by a survey of several thematic areas. The accompanying examples illustrate the importance of SED in the history of statistics, measurements and standards: calibration and measurement assurance, interlaboratory tests, development of measurement methods, Standard Reference Materials, statistical computing, and dissemination of measurement technology. A brief look forward sketches the expanding opportunity and demand for SED statisticians created by current trends in research and development at NIST. PMID:27500023
NASA Astrophysics Data System (ADS)
Frimann, S.; Jørgensen, J. K.; Haugbølle, T.
2016-02-01
Context. Both observations and simulations of embedded protostars have progressed rapidly in recent years. Bringing them together is an important step in advancing our knowledge about the earliest phases of star formation. Aims: To compare synthetic continuum images and spectral energy distributions (SEDs), calculated from large-scale numerical simulations, to observational studies, thereby aiding in both the interpretation of the observations and in testing the fidelity of the simulations. Methods: The adaptive mesh refinement code, RAMSES, is used to simulate the evolution of a 5 pc × 5 pc × 5 pc molecular cloud. The simulation has a maximum resolution of 8 AU, resolving simultaneously the molecular cloud on parsec scales and individual protostellar systems on AU scales. The simulation is post-processed with the radiative transfer code RADMC-3D, which is used to create synthetic continuum images and SEDs of the protostellar systems. In this way, more than 13 000 unique radiative transfer models, of a variety of different protostellar systems, are produced. Results: Over the course of 0.76 Myr the simulation forms more than 500 protostars, primarily within two sub-clusters. The synthetic SEDs are used to calculate evolutionary tracers Tbol and Lsmm/Lbol. It is shown that, while the observed distributions of the tracers are well matched by the simulation, they generally do a poor job of tracking the protostellar ages. Disks form early in the simulation, with 40% of the Class 0 protostars being encircled by one. The flux emission from the simulated disks is found to be, on average, a factor ~6 too low relative to real observations; an issue that can be traced back to numerical effects on the smallest scales in the simulation. The simulated distribution of protostellar luminosities spans more than three order of magnitudes, similar to the observed distribution. Cores and protostars are found to be closely associated with one another, with the distance distribution
NASA Astrophysics Data System (ADS)
Goodman, Joseph W.
2000-07-01
The Wiley Classics Library consists of selected books that have become recognized classics in their respective fields. With these new unabridged and inexpensive editions, Wiley hopes to extend the life of these important works by making them available to future generations of mathematicians and scientists. Currently available in the Series: T. W. Anderson The Statistical Analysis of Time Series T. S. Arthanari & Yadolah Dodge Mathematical Programming in Statistics Emil Artin Geometric Algebra Norman T. J. Bailey The Elements of Stochastic Processes with Applications to the Natural Sciences Robert G. Bartle The Elements of Integration and Lebesgue Measure George E. P. Box & Norman R. Draper Evolutionary Operation: A Statistical Method for Process Improvement George E. P. Box & George C. Tiao Bayesian Inference in Statistical Analysis R. W. Carter Finite Groups of Lie Type: Conjugacy Classes and Complex Characters R. W. Carter Simple Groups of Lie Type William G. Cochran & Gertrude M. Cox Experimental Designs, Second Edition Richard Courant Differential and Integral Calculus, Volume I RIchard Courant Differential and Integral Calculus, Volume II Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume I Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume II D. R. Cox Planning of Experiments Harold S. M. Coxeter Introduction to Geometry, Second Edition Charles W. Curtis & Irving Reiner Representation Theory of Finite Groups and Associative Algebras Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume I Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume II Cuthbert Daniel Fitting Equations to Data: Computer Analysis of Multifactor Data, Second Edition Bruno de Finetti Theory of Probability, Volume I Bruno de Finetti Theory of Probability, Volume 2 W. Edwards Deming Sample Design in Business Research
NASA Technical Reports Server (NTRS)
da Silva, Arlindo M.; Norris, Peter M.
2013-01-01
Part I presented a Monte Carlo Bayesian method for constraining a complex statistical model of GCM sub-gridcolumn moisture variability using high-resolution MODIS cloud data, thereby permitting large-scale model parameter estimation and cloud data assimilation. This part performs some basic testing of this new approach, verifying that it does indeed significantly reduce mean and standard deviation biases with respect to the assimilated MODIS cloud optical depth, brightness temperature and cloud top pressure, and that it also improves the simulated rotational-Ramman scattering cloud optical centroid pressure (OCP) against independent (non-assimilated) retrievals from the OMI instrument. Of particular interest, the Monte Carlo method does show skill in the especially difficult case where the background state is clear but cloudy observations exist. In traditional linearized data assimilation methods, a subsaturated background cannot produce clouds via any infinitesimal equilibrium perturbation, but the Monte Carlo approach allows finite jumps into regions of non-zero cloud probability. In the example provided, the method is able to restore marine stratocumulus near the Californian coast where the background state has a clear swath. This paper also examines a number of algorithmic and physical sensitivities of the new method and provides guidance for its cost-effective implementation. One obvious difficulty for the method, and other cloud data assimilation methods as well, is the lack of information content in the cloud observables on cloud vertical structure, beyond cloud top pressure and optical thickness, thus necessitating strong dependence on the background vertical moisture structure. It is found that a simple flow-dependent correlation modification due to Riishojgaard (1998) provides some help in this respect, by better honoring inversion structures in the background state.
Thoughts About Theories and Statistics.
Fawcett, Jacqueline
2015-07-01
The purpose of this essay is to share my ideas about the connection between theories and statistics. The essay content reflects my concerns about some researchers' and readers' apparent lack of clarity about what constitutes appropriate statistical testing and conclusions about the empirical adequacy of theories. The reciprocal relation between theories and statistics is emphasized and the conclusion is that statistics without direction from theory is no more than a hobby.
1986-01-01
Official population data for the USSR are presented for 1985 and 1986. Part 1 (pp. 65-72) contains data on capitals of union republics and cities with over one million inhabitants, including population estimates for 1986 and vital statistics for 1985. Part 2 (p. 72) presents population estimates by sex and union republic, 1986. Part 3 (pp. 73-6) presents data on population growth, including birth, death, and natural increase rates, 1984-1985; seasonal distribution of births and deaths; birth order; age-specific birth rates in urban and rural areas and by union republic; marriages; age at marriage; and divorces. PMID:12178831
NASA Astrophysics Data System (ADS)
Grégoire, G.
2016-05-01
This chapter is devoted to two objectives. The first one is to answer the request expressed by attendees of the first Astrostatistics School (Annecy, October 2013) to be provided with an elementary vademecum of statistics that would facilitate understanding of the given courses. In this spirit we recall very basic notions, that is definitions and properties that we think sufficient to benefit from courses given in the Astrostatistical School. Thus we give briefly definitions and elementary properties on random variables and vectors, distributions, estimation and tests, maximum likelihood methodology. We intend to present basic ideas in a hopefully comprehensible way. We do not try to give a rigorous presentation, and due to the place devoted to this chapter, can cover only a rather limited field of statistics. The second aim is to focus on some statistical tools that are useful in classification: basic introduction to Bayesian statistics, maximum likelihood methodology, Gaussian vectors and Gaussian mixture models.
Pekney, Natalie J.; Cheng, Hanqi; Small, Mitchell J.
2015-11-05
Abstract: The objective of the current work was to develop a statistical method and associated tool to evaluate the impact of oil and natural gas exploration and production activities on local air quality.
ASURV: Astronomical SURVival Statistics
NASA Astrophysics Data System (ADS)
Feigelson, E. D.; Nelson, P. I.; Isobe, T.; LaValley, M.
2014-06-01
ASURV (Astronomical SURVival Statistics) provides astronomy survival analysis for right- and left-censored data including the maximum-likelihood Kaplan-Meier estimator and several univariate two-sample tests, bivariate correlation measures, and linear regressions. ASURV is written in FORTRAN 77, and is stand-alone and does not call any specialized libraries.
ERIC Educational Resources Information Center
Osler, James Edward; Waden, Carl
2013-01-01
This paper discusses the implementation of the Tri-Squared Test as one of many advanced statistical measures used to verify and validate the outcomes of an initial study on academic professional's perspectives on the use, success, and viability of 9th Grade Freshman Academies, Centers, and Center Models. The initial research investigation…
NASA Astrophysics Data System (ADS)
Sabil, M.; Benkhaldoun, Z.; Lazrek, M.; Habib, A.; Hach, Y.; Benhida, A.; Jabiri, A.; Elazhari, Y.
2014-07-01
In this paper we present an analysis of the statistical and temporal properties of seeing and isoplanatic angle measurements obtained with combined Differential Image Motion Monitor (DIMM) and Multi-Aperture Scintillation Sensor (MASS) at Jbel Aklim candidate site for the Eauropean Extremely Large Telescope (E-ELT). These data have been collected from February 2008 to Jun 2010. The overall seeing statistics for Jbel Aklim site are presented, broken into total seeing, free atmosphere seeing and isoplanatic angle, and ground-layer seeing (difference between the total and free-atmosphere seeing). We examine the statistical distributions of seeing measurements and investigate annual and nightly behavior. The properties of the seeing measurements are discussed in terms of the geography and meteorological conditions at Jbel Aklim site.
ERIC Educational Resources Information Center
Texeira, Antonio; Rosa, Alvaro; Calapez, Teresa
2009-01-01
This article presents statistical power analysis (SPA) based on the normal distribution using Excel, adopting textbook and SPA approaches. The objective is to present the latter in a comparative way within a framework that is familiar to textbook level readers, as a first step to understand SPA with other distributions. The analysis focuses on the…
Candidate Assembly Statistical Evaluation
1998-07-15
The Savannah River Site (SRS) receives aluminum clad spent Material Test Reactor (MTR) fuel from all over the world for storage and eventual reprocessing. There are hundreds of different kinds of MTR fuels and these fuels will continue to be received at SRS for approximately ten more years. SRS''s current criticality evaluation methodology requires the modeling of all MTR fuels utilizing Monte Carlo codes, which is extremely time consuming and resource intensive. Now that amore » significant number of MTR calculations have been conducted it is feasible to consider building statistical models that will provide reasonable estimations of MTR behavior. These statistical models can be incorporated into a standardized model homogenization spreadsheet package to provide analysts with a means of performing routine MTR fuel analyses with a minimal commitment of time and resources. This became the purpose for development of the Candidate Assembly Statistical Evaluation (CASE) program at SRS.« less
NASA Astrophysics Data System (ADS)
Sánchez, L. J.; Cruz-González, I.; Echevarría, J.; Ruelas-Mayorga, A.; García, A. M.; Avila, R.; Carrasco, E.; Carramiñana, A.; Nigoche-Netro, A.
2012-10-01
We present comprehensive seeing statistics for the San Pedro Mártir site derived from the Thirty Meter Telescope site-selection data. The observations were obtained between 2004 and 2008 with a Differential Image Motion Monitor (DIMM) and a Multi-Aperture Scintillation Sensor (MASS) combined instrument (MASS-DIMM). The parameters that are statistically analysed here are the whole atmosphere seeing (measured by the DIMM), the free atmosphere seeing (measured by the MASS) and the ground-layer (GL) seeing, which is the difference between the total seeing and the free atmosphere seeing. We have made a careful data coverage study, along with statistical distributions of simultaneous MASS-DIMM seeing measurements, in order to investigate the nightly, monthly, seasonal, annual and global behaviour, as well as possible hourly seeing trends. Although this campaign covers five years, the sampling is uneven, with 2006 and 2007 being the best sampled years in terms of seasonal coverage. The overall results yield a median seeing of 0.78 arcsec (DIMM), 0.37 arcsec (MASS) and 0.59 arcsec (GL). Therefore, the strongest contribution to the whole atmosphere seeing comes from a strong ground layer. We find that the best season is summer, while the worst season is winter, in accordance with previous studies. It is worth noting that the best yearly results are correlated with the best sampled years. The hourly analysis shows that there is no statistically significant tendency for seeing degradation towards dawn. The seeing values are slightly larger than those reported previously, which might be the result of climate changes. Based on observations obtained at the Observatorio Astronómico Nacional at San Pedro Mártir, Baja California, México, operated by the Instituto de Astronomía, Universidad Nacional Autónoma de México.
Research Design and Statistical Design.
ERIC Educational Resources Information Center
Szymanski, Edna Mora
1993-01-01
Presents fourth editorial in series, this one describing research design and explaining its relationship to statistical design. Research design, validity, and research approaches are examined, quantitative research designs and hypothesis testing are described, and control and statistical designs are discussed. Concludes with section on the art of…
Cooley, Laura A.; Oster, Alexandra M.; Rose, Charles E.; Wejnert, Cyprian; Le, Binh C.; Paz-Bailey, Gabriela
2014-01-01
In 2011, 62% of estimated new HIV diagnoses in the United States were attributed to male-to-male sexual contact (men who have sex with men, MSM); 39% of these MSM were black or African American. HIV testing, recommended at least annually by CDC for sexually active MSM, is an essential first step in HIV care and treatment for HIV-positive individuals. A variety of HIV testing initiatives, designed to reach populations disproportionately affected by HIV, have been developed at both national and local levels. We assessed changes in HIV testing behavior among MSM participating in the National HIV Behavioral Surveillance System in 2008 and 2011. We compared the percentages tested in the previous 12 months in 2008 and 2011, overall and by race/ethnicity and age group. In unadjusted analyses, recent HIV testing increased from 63% in 2008 to 67% in 2011 overall (P<0.001), from 63% to 71% among black MSM (P<0.001), and from 63% to 75% among MSM of other/multiple races (P<0.001); testing did not increase significantly for white or Hispanic/Latino MSM. Multivariable model results indicated an overall increase in recent HIV testing (adjusted prevalence ratio [aPR] = 1.07, P<0.001). Increases were largest for black MSM (aPR = 1.12, P<0.001) and MSM of other/multiple races (aPR = 1.20, P<0.001). Among MSM aged 18–19 years, recent HIV testing was shown to increase significantly among black MSM (aPR = 1.20, P = 0.007), but not among MSM of other racial/ethnic groups. Increases in recent HIV testing among populations most affected by HIV are encouraging, but despite these increases, improved testing coverage is needed to meet CDC recommendations. PMID:25180514
Cosmetic Plastic Surgery Statistics
2014 Cosmetic Plastic Surgery Statistics Cosmetic Procedure Trends 2014 Plastic Surgery Statistics Report Please credit the AMERICAN SOCIETY OF PLASTIC SURGEONS when citing statistical data or using ...
Adding a Statistical Wrench to the "Toolbox"
ERIC Educational Resources Information Center
DesJardins, Stephen L.; Lindsay, Nathan K.
2008-01-01
This paper demonstrates a formal statistical test that can be used to help researchers make decisions about alternative statistical model specifications. This test is commonly used by researchers who would like to test whether adding new variables to a model improves the model fit. However, we demonstrate that this formal test can also be employed…
Guo, Junfeng; Wang, Chao; Chan, Kung-Sik; Jin, Dakai; Saha, Punam K.; Sieren, Jered P.; Barr, R. G.; Han, MeiLan K.; Kazerooni, Ella; Cooper, Christopher B.; Couper, David; Hoffman, Eric A.
2016-01-01
Purpose: A test object (phantom) is an important tool to evaluate comparability and stability of CT scanners used in multicenter and longitudinal studies. However, there are many sources of error that can interfere with the test object-derived quantitative measurements. Here the authors investigated three major possible sources of operator error in the use of a test object employed to assess pulmonary density-related as well as airway-related metrics. Methods: Two kinds of experiments were carried out to assess measurement variability caused by imperfect scanning status. The first one consisted of three experiments. A COPDGene test object was scanned using a dual source multidetector computed tomographic scanner (Siemens Somatom Flash) with the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) inspiration protocol (120 kV, 110 mAs, pitch = 1, slice thickness = 0.75 mm, slice spacing = 0.5 mm) to evaluate the effects of tilt angle, water bottle offset, and air bubble size. After analysis of these results, a guideline was reached in order to achieve more reliable results for this test object. Next the authors applied the above findings to 2272 test object scans collected over 4 years as part of the SPIROMICS study. The authors compared changes of the data consistency before and after excluding the scans that failed to pass the guideline. Results: This study established the following limits for the test object: tilt index ≤0.3, water bottle offset limits of [−6.6 mm, 7.4 mm], and no air bubble within the water bottle, where tilt index is a measure incorporating two tilt angles around x- and y-axis. With 95% confidence, the density measurement variation for all five interested materials in the test object (acrylic, water, lung, inside air, and outside air) resulting from all three error sources can be limited to ±0.9 HU (summed in quadrature), when all the requirements are satisfied. The authors applied these criteria to 2272 SPIROMICS
ERIC Educational Resources Information Center
Kromrey, Jeffrey D.; Dickinson, Wendy B.
1996-01-01
Empirical estimates of the power and Type I error rate of the test of the classrooms-within-treatments effect in the nested analysis of variance approach are provided for a variety of nominal alpha levels and a range of classroom effect sizes and research designs. (SLD)
ERIC Educational Resources Information Center
Pollock, Judith M.; And Others
This report describes an experiment in constructed response testing undertaken in conjunction with the National Education Longitudinal Study of 1988 (NELS:88). Constructed response questions are those that require students to produce their own response rather than selecting the correct answer from several options. Participants in this experiment…
Snedeker, Jess G; Muser, Markus H; Walz, Felix H
2003-10-01
In this study, we first present a comparison between pelvis/upper leg injuries observed in real-world accidents as recorded in the database of the Medical University of Hanover, and the EEVC test results of corresponding cars as published by EuroNCAP. The fact that modern cars with rounded hood edges cause very few pelvis/upper leg injuries is discussed against the findings of the EEVC tests, where these cars do not perform significantly better than their older counterparts with sharper hood leading edges. This discrepancy could be due to the fact that the radius of the hood edge is not accounted for in the current version of the test protocol. In a second step, various impacts against several different simplified hood shapes were simulated using a detailed finite element model of a 50(th) percentile male pedestrian. The finite element model (THUMS) has been extensively validated against PMHS experiments in previous studies. The validated model affords detailed insight into pelvic and femoral deformations and loading patterns, and reveals, as expected, that the shape of the hood leading edge plays a critical role in the resulting biomechanical loading patterns. Based upon the results of this study, recommendations are offered for a more appropriate characterization of the hood shape with regard to pelvis/upper leg injury risk. PMID:17096259
Snedeker, Jess G; Muser, Markus H; Walz, Felix H
2003-10-01
In this study, we first present a comparison between pelvis/upper leg injuries observed in real-world accidents as recorded in the database of the Medical University of Hanover, and the EEVC test results of corresponding cars as published by EuroNCAP. The fact that modern cars with rounded hood edges cause very few pelvis/upper leg injuries is discussed against the findings of the EEVC tests, where these cars do not perform significantly better than their older counterparts with sharper hood leading edges. This discrepancy could be due to the fact that the radius of the hood edge is not accounted for in the current version of the test protocol. In a second step, various impacts against several different simplified hood shapes were simulated using a detailed finite element model of a 50(th) percentile male pedestrian. The finite element model (THUMS) has been extensively validated against PMHS experiments in previous studies. The validated model affords detailed insight into pelvic and femoral deformations and loading patterns, and reveals, as expected, that the shape of the hood leading edge plays a critical role in the resulting biomechanical loading patterns. Based upon the results of this study, recommendations are offered for a more appropriate characterization of the hood shape with regard to pelvis/upper leg injury risk.
Predict! Teaching Statistics Using Informational Statistical Inference
ERIC Educational Resources Information Center
Makar, Katie
2013-01-01
Statistics is one of the most widely used topics for everyday life in the school mathematics curriculum. Unfortunately, the statistics taught in schools focuses on calculations and procedures before students have a chance to see it as a useful and powerful tool. Researchers have found that a dominant view of statistics is as an assortment of tools…
SOCR: Statistics Online Computational Resource
Dinov, Ivo D.
2011-01-01
The need for hands-on computer laboratory experience in undergraduate and graduate statistics education has been firmly established in the past decade. As a result a number of attempts have been undertaken to develop novel approaches for problem-driven statistical thinking, data analysis and result interpretation. In this paper we describe an integrated educational web-based framework for: interactive distribution modeling, virtual online probability experimentation, statistical data analysis, visualization and integration. Following years of experience in statistical teaching at all college levels using established licensed statistical software packages, like STATA, S-PLUS, R, SPSS, SAS, Systat, etc., we have attempted to engineer a new statistics education environment, the Statistics Online Computational Resource (SOCR). This resource performs many of the standard types of statistical analysis, much like other classical tools. In addition, it is designed in a plug-in object-oriented architecture and is completely platform independent, web-based, interactive, extensible and secure. Over the past 4 years we have tested, fine-tuned and reanalyzed the SOCR framework in many of our undergraduate and graduate probability and statistics courses and have evidence that SOCR resources build student’s intuition and enhance their learning. PMID:21451741
... Abroad Treatment Basic Statistics Get Tested Find an HIV testing site near you. Enter ZIP code or city Follow HIV/AIDS CDC HIV CDC HIV/AIDS See RSS | ... Collapse All How many people are diagnosed with HIV each year in the United States? In 2014, ...
Ranald Macdonald and statistical inference.
Smith, Philip T
2009-05-01
Ranald Roderick Macdonald (1945-2007) was an important contributor to mathematical psychology in the UK, as a referee and action editor for British Journal of Mathematical and Statistical Psychology and as a participant and organizer at the British Psychological Society's Mathematics, statistics and computing section meetings. This appreciation argues that his most important contribution was to the foundations of significance testing, where his concern about what information was relevant in interpreting the results of significance tests led him to be a persuasive advocate for the 'Weak Fisherian' form of hypothesis testing. PMID:19351454
The Statistical Loop Analyzer (SLA)
NASA Technical Reports Server (NTRS)
Lindsey, W. C.
1985-01-01
The statistical loop analyzer (SLA) is designed to automatically measure the acquisition, tracking and frequency stability performance characteristics of symbol synchronizers, code synchronizers, carrier tracking loops, and coherent transponders. Automated phase lock and system level tests can also be made using the SLA. Standard baseband, carrier and spread spectrum modulation techniques can be accomodated. Through the SLA's phase error jitter and cycle slip measurements the acquisition and tracking thresholds of the unit under test are determined; any false phase and frequency lock events are statistically analyzed and reported in the SLA output in probabilistic terms. Automated signal drop out tests can be performed in order to trouble shoot algorithms and evaluate the reacquisition statistics of the unit under test. Cycle slip rates and cycle slip probabilities can be measured using the SLA. These measurements, combined with bit error probability measurements, are all that are needed to fully characterize the acquisition and tracking performance of a digital communication system.
Guta, Madalin; Butucea, Cristina
2010-10-15
The notion of a U-statistic for an n-tuple of identical quantum systems is introduced in analogy to the classical (commutative) case: given a self-adjoint 'kernel' K acting on (C{sup d}){sup '}x{sup r} with r
Hasegawa, Takahiro
2016-09-01
In recent years, immunological science has evolved, and cancer vaccines are now approved and available for treating existing cancers. Because cancer vaccines require time to elicit an immune response, a delayed treatment effect is expected and is actually observed in drug approval studies. Accordingly, we propose the evaluation of survival endpoints by weighted log-rank tests with the Fleming-Harrington class of weights. We consider group sequential monitoring, which allows early efficacy stopping, and determine a semiparametric information fraction for the Fleming-Harrington family of weights, which is necessary for the error spending function. Moreover, we give a flexible survival model in cancer vaccine studies that considers not only the delayed treatment effect but also the long-term survivors. In a Monte Carlo simulation study, we illustrate that when the primary analysis is a weighted log-rank test emphasizing the late differences, the proposed information fraction can be a useful alternative to the surrogate information fraction, which is proportional to the number of events. Copyright © 2016 John Wiley & Sons, Ltd.
Delaunois, L; Lulling, J; Prignot, J
1976-01-01
Among 65 patients admitted to the hospital for chronic obstructive lung disease, the following pulmonary tests were systematically performed : spirometric vital capacity and total lung capacity, FEV1, functional residual capacity and total lung capacity measured by body plethysmography, airway resistance and specific conductance, CO diffusion capacity measured by single-breath test, N2 clearance by single breath oxygen dilution, and blood gases. The patients were divided into bronchitics, emphysematous and broncho-emphysematous, according to the clinical and radiological Nash's score, and to another personal score derived from the former. The simple and multiple correlations between the clinico-radiological score and the functional results are low. The clustering analysis groups the 65 patients into four clouds of points, around two principal axes : the volume axis and the overinflation axis. This study indicates that the most suggestive results for emphysema diagnosis are increased FRC and TLC and low Tlco/V'a. The clinical score is not dominant for the clustering of the patients into the dynamic clouds. Beneath the bronchitic, the broncho-emphysematous and the emphysematous groups, the clustering analysis individualizes a fourth group of cases characterized by chronic asthma, and which were not isolated by Nash's score.
Statistical Methods in Cosmology
NASA Astrophysics Data System (ADS)
Verde, L.
2010-03-01
The advent of large data-set in cosmology has meant that in the past 10 or 20 years our knowledge and understanding of the Universe has changed not only quantitatively but also, and most importantly, qualitatively. Cosmologists rely on data where a host of useful information is enclosed, but is encoded in a non-trivial way. The challenges in extracting this information must be overcome to make the most of a large experimental effort. Even after having converged to a standard cosmological model (the LCDM model) we should keep in mind that this model is described by 10 or more physical parameters and if we want to study deviations from it, the number of parameters is even larger. Dealing with such a high dimensional parameter space and finding parameters constraints is a challenge on itself. Cosmologists want to be able to compare and combine different data sets both for testing for possible disagreements (which could indicate new physics) and for improving parameter determinations. Finally, cosmologists in many cases want to find out, before actually doing the experiment, how much one would be able to learn from it. For all these reasons, sophisiticated statistical techniques are being employed in cosmology, and it has become crucial to know some statistical background to understand recent literature in the field. I will introduce some statistical tools that any cosmologist should know about in order to be able to understand recently published results from the analysis of cosmological data sets. I will not present a complete and rigorous introduction to statistics as there are several good books which are reported in the references. The reader should refer to those.
Schultheiss, Oliver C; Yankova, Diana; Dirlikov, Benjamin; Schad, Daniel J
2009-01-01
Previous studies that have examined the relationship between implicit and explicit motive measures have consistently found little variance overlap between both types of measures regardless of thematic content domain (i.e., power, achievement, affiliation). However, this independence may be artifactual because the primary means of measuring implicit motives--content-coding stories people write about picture cues--are incommensurable with the primary means of measuring explicit motives: having individuals fill out self-report scales. To provide a better test of the presumed independence between both types of measures, we measured implicit motives with a Picture Story Exercise (PSE; McClelland, Koestner, & Weinberger, 1989) and explicit motives with a cue- and response-matched questionnaire version of the PSE (PSE-Q) and a traditional measure of explicit motives, the Personality Research Form (PRF; Jackson, 1984) in 190 research participants. Correlations between the PSE and the PSE-Q were small and mostly nonsignificant, whereas the PSE-Q showed significant variance overlap with the PRF within and across thematic domains. We conclude that the independence postulate holds even when more commensurable measures of implicit and explicit motives are used.
Recent statistical methods for orientation data
NASA Technical Reports Server (NTRS)
Batschelet, E.
1972-01-01
The application of statistical methods for determining the areas of animal orientation and navigation are discussed. The method employed is limited to the two-dimensional case. Various tests for determining the validity of the statistical analysis are presented. Mathematical models are included to support the theoretical considerations and tables of data are developed to show the value of information obtained by statistical analysis.
Statistical Reference Datasets
National Institute of Standards and Technology Data Gateway
Statistical Reference Datasets (Web, free access) The Statistical Reference Datasets is also supported by the Standard Reference Data Program. The purpose of this project is to improve the accuracy of statistical software by providing reference datasets with certified computational results that enable the objective evaluation of statistical software.
Statistical modeling of software reliability
NASA Technical Reports Server (NTRS)
Miller, Douglas R.
1992-01-01
This working paper discusses the statistical simulation part of a controlled software development experiment being conducted under the direction of the System Validation Methods Branch, Information Systems Division, NASA Langley Research Center. The experiment uses guidance and control software (GCS) aboard a fictitious planetary landing spacecraft: real-time control software operating on a transient mission. Software execution is simulated to study the statistical aspects of reliability and other failure characteristics of the software during development, testing, and random usage. Quantification of software reliability is a major goal. Various reliability concepts are discussed. Experiments are described for performing simulations and collecting appropriate simulated software performance and failure data. This data is then used to make statistical inferences about the quality of the software development and verification processes as well as inferences about the reliability of software versions and reliability growth under random testing and debugging.
Developments in Statistical Education.
ERIC Educational Resources Information Center
Kapadia, Ramesh
1980-01-01
The current status of statistics education at the secondary level is reviewed, with particular attention focused on the various instructional programs in England. A description and preliminary evaluation of the Schools Council Project on Statistical Education is included. (MP)
Mathematical and statistical analysis
NASA Technical Reports Server (NTRS)
Houston, A. Glen
1988-01-01
The goal of the mathematical and statistical analysis component of RICIS is to research, develop, and evaluate mathematical and statistical techniques for aerospace technology applications. Specific research areas of interest include modeling, simulation, experiment design, reliability assessment, and numerical analysis.
On More Sensitive Periodogram Statistics
NASA Astrophysics Data System (ADS)
Bélanger, G.
2016-05-01
Period searches in event data have traditionally used the Rayleigh statistic, R 2. For X-ray pulsars, the standard has been the Z 2 statistic, which sums over more than one harmonic. For γ-rays, the H-test, which optimizes the number of harmonics to sum, is often used. These periodograms all suffer from the same problem, namely artifacts caused by correlations in the Fourier components that arise from testing frequencies with a non-integer number of cycles. This article addresses this problem. The modified Rayleigh statistic is discussed, its generalization to any harmonic, {{ R }}k2, is formulated, and from the latter, the modified Z 2 statistic, {{ Z }}2, is constructed. Versions of these statistics for binned data and point measurements are derived, and it is shown that the variance in the uncertainties can have an important influence on the periodogram. It is shown how to combine the information about the signal frequency from the different harmonics to estimate its value with maximum accuracy. The methods are applied to an XMM-Newton observation of the Crab pulsar for which a decomposition of the pulse profile is presented, and shows that most of the power is in the second, third, and fifth harmonics. Statistical detection power of the {{ R }}k2 statistic is superior to the FFT and equivalent to the Lomb--Scargle (LS). Response to gaps in the data is assessed, and it is shown that the LS does not protect against the distortions they cause. The main conclusion of this work is that the classical R 2 and Z 2 should be replaced by {{ R }}k2 and {{ Z }}2 in all applications with event data, and the LS should be replaced by the {{ R }}k2 when the uncertainty varies from one point measurement to another.
ERIC Educational Resources Information Center
Bopp, Richard E.; Van Der Laan, Sharon J.
1985-01-01
Presents a search strategy for locating time-series or cross-sectional statistical data in published sources which was designed for undergraduate students who require 30 units of data for five separate variables in a statistical model. Instructional context and the broader applicability of the search strategy for general statistical research is…
ERIC Educational Resources Information Center
Strasser, Nora
2007-01-01
Avoiding statistical mistakes is important for educators at all levels. Basic concepts will help you to avoid making mistakes using statistics and to look at data with a critical eye. Statistical data is used at educational institutions for many purposes. It can be used to support budget requests, changes in educational philosophy, changes to…
ERIC Educational Resources Information Center
Lenard, Christopher; McCarthy, Sally; Mills, Terence
2014-01-01
There are many different aspects of statistics. Statistics involves mathematics, computing, and applications to almost every field of endeavour. Each aspect provides an opportunity to spark someone's interest in the subject. In this paper we discuss some ethical aspects of statistics, and describe how an introduction to ethics has been…
Statistical quality management
NASA Astrophysics Data System (ADS)
Vanderlaan, Paul
1992-10-01
Some aspects of statistical quality management are discussed. Quality has to be defined as a concrete, measurable quantity. The concepts of Total Quality Management (TQM), Statistical Process Control (SPC), and inspection are explained. In most cases SPC is better than inspection. It can be concluded that statistics has great possibilities in the field of TQM.
Statistical prediction of cyclostationary processes
Kim, K.Y.
2000-03-15
Considered in this study is a cyclostationary generalization of an EOF-based prediction method. While linear statistical prediction methods are typically optimal in the sense that prediction error variance is minimal within the assumption of stationarity, there is some room for improved performance since many physical processes are not stationary. For instance, El Nino is known to be strongly phase locked with the seasonal cycle, which suggests nonstationarity of the El Nino statistics. Many geophysical and climatological processes may be termed cyclostationary since their statistics show strong cyclicity instead of stationarity. Therefore, developed in this study is a cyclostationary prediction method. Test results demonstrate that performance of prediction methods can be improved significantly by accounting for the cyclostationarity of underlying processes. The improvement comes from an accurate rendition of covariance structure both in space and time.
Which statistics should tropical biologists learn?
Loaiza Velásquez, Natalia; González Lutz, María Isabel; Monge-Nájera, Julián
2011-09-01
Tropical biologists study the richest and most endangered biodiversity in the planet, and in these times of climate change and mega-extinctions, the need for efficient, good quality research is more pressing than in the past. However, the statistical component in research published by tropical authors sometimes suffers from poor quality in data collection; mediocre or bad experimental design and a rigid and outdated view of data analysis. To suggest improvements in their statistical education, we listed all the statistical tests and other quantitative analyses used in two leading tropical journals, the Revista de Biología Tropical and Biotropica, during a year. The 12 most frequent tests in the articles were: Analysis of Variance (ANOVA), Chi-Square Test, Student's T Test, Linear Regression, Pearson's Correlation Coefficient, Mann-Whitney U Test, Kruskal-Wallis Test, Shannon's Diversity Index, Tukey's Test, Cluster Analysis, Spearman's Rank Correlation Test and Principal Component Analysis. We conclude that statistical education for tropical biologists must abandon the old syllabus based on the mathematical side of statistics and concentrate on the correct selection of these and other procedures and tests, on their biological interpretation and on the use of reliable and friendly freeware. We think that their time will be better spent understanding and protecting tropical ecosystems than trying to learn the mathematical foundations of statistics: in most cases, a well designed one-semester course should be enough for their basic requirements.
Statistical methods for material characterization and qualification
Hunn, John D; Kercher, Andrew K
2005-01-01
This document describes a suite of statistical methods that can be used to infer lot parameters from the data obtained from inspection/testing of random samples taken from that lot. Some of these methods will be needed to perform the statistical acceptance tests required by the Advanced Gas Reactor Fuel Development and Qualification (AGR) Program. Special focus has been placed on proper interpretation of acceptance criteria and unambiguous methods of reporting the statistical results. In addition, modified statistical methods are described that can provide valuable measures of quality for different lots of material. This document has been written for use as a reference and a guide for performing these statistical calculations. Examples of each method are provided. Uncertainty analysis (e.g., measurement uncertainty due to instrumental bias) is not included in this document, but should be considered when reporting statistical results.
Statistical Methods for Material Characterization and Qualification
Kercher, A.K.
2005-04-01
This document describes a suite of statistical methods that can be used to infer lot parameters from the data obtained from inspection/testing of random samples taken from that lot. Some of these methods will be needed to perform the statistical acceptance tests required by the Advanced Gas Reactor Fuel Development and Qualification (AGR) Program. Special focus has been placed on proper interpretation of acceptance criteria and unambiguous methods of reporting the statistical results. In addition, modified statistical methods are described that can provide valuable measures of quality for different lots of material. This document has been written for use as a reference and a guide for performing these statistical calculations. Examples of each method are provided. Uncertainty analysis (e.g., measurement uncertainty due to instrumental bias) is not included in this document, but should be considered when reporting statistical results.
Statistical methods in language processing.
Abney, Steven
2011-05-01
The term statistical methods here refers to a methodology that has been dominant in computational linguistics since about 1990. It is characterized by the use of stochastic models, substantial data sets, machine learning, and rigorous experimental evaluation. The shift to statistical methods in computational linguistics parallels a movement in artificial intelligence more broadly. Statistical methods have so thoroughly permeated computational linguistics that almost all work in the field draws on them in some way. There has, however, been little penetration of the methods into general linguistics. The methods themselves are largely borrowed from machine learning and information theory. We limit attention to that which has direct applicability to language processing, though the methods are quite general and have many nonlinguistic applications. Not every use of statistics in language processing falls under statistical methods as we use the term. Standard hypothesis testing and experimental design, for example, are not covered in this article. WIREs Cogni Sci 2011 2 315-322 DOI: 10.1002/wcs.111 For further resources related to this article, please visit the WIREs website.
Statistical Mechanics of Zooplankton.
Hinow, Peter; Nihongi, Ai; Strickler, J Rudi
2015-01-01
Statistical mechanics provides the link between microscopic properties of many-particle systems and macroscopic properties such as pressure and temperature. Observations of similar "microscopic" quantities exist for the motion of zooplankton, as well as many species of other social animals. Herein, we propose to take average squared velocities as the definition of the "ecological temperature" of a population under different conditions on nutrients, light, oxygen and others. We test the usefulness of this definition on observations of the crustacean zooplankton Daphnia pulicaria. In one set of experiments, D. pulicaria is infested with the pathogen Vibrio cholerae, the causative agent of cholera. We find that infested D. pulicaria under light exposure have a significantly greater ecological temperature, which puts them at a greater risk of detection by visual predators. In a second set of experiments, we observe D. pulicaria in cold and warm water, and in darkness and under light exposure. Overall, our ecological temperature is a good discriminator of the crustacean's swimming behavior.
Statistical Mechanics of Zooplankton
Hinow, Peter; Nihongi, Ai; Strickler, J. Rudi
2015-01-01
Statistical mechanics provides the link between microscopic properties of many-particle systems and macroscopic properties such as pressure and temperature. Observations of similar “microscopic” quantities exist for the motion of zooplankton, as well as many species of other social animals. Herein, we propose to take average squared velocities as the definition of the “ecological temperature” of a population under different conditions on nutrients, light, oxygen and others. We test the usefulness of this definition on observations of the crustacean zooplankton Daphnia pulicaria. In one set of experiments, D. pulicaria is infested with the pathogen Vibrio cholerae, the causative agent of cholera. We find that infested D. pulicaria under light exposure have a significantly greater ecological temperature, which puts them at a greater risk of detection by visual predators. In a second set of experiments, we observe D. pulicaria in cold and warm water, and in darkness and under light exposure. Overall, our ecological temperature is a good discriminator of the crustacean’s swimming behavior. PMID:26270537
Tannery, Nancy Hrinya; Silverman, Deborah L; Epstein, Barbara A
2002-01-01
Online use statistics can provide libraries with a tool to be used when developing an online collection of resources. Statistics can provide information on overall use of a collection, individual print and electronic journal use, and collection use by specific user populations. They can also be used to determine the number of user licenses to purchase. This paper focuses on the issue of use statistics made available for one collection of online resources.
Statistical distribution sampling
NASA Technical Reports Server (NTRS)
Johnson, E. S.
1975-01-01
Determining the distribution of statistics by sampling was investigated. Characteristic functions, the quadratic regression problem, and the differential equations for the characteristic functions are analyzed.
ERIC Educational Resources Information Center
Ciftci, S. Koza; Karadag, Engin; Akdal, Pinar
2014-01-01
The purpose of this study was to determine the effect of statistics instruction using computer-based tools, on statistics anxiety, attitude, and achievement. This study was designed as quasi-experimental research and the pattern used was a matched pre-test/post-test with control group design. Data was collected using three scales: a Statistics…
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Statistics. 1065.602 Section 1065.602 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.602 Statistics. (a) Overview. This section...
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Statistics. 1065.602 Section 1065.602 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.602 Statistics. (a) Overview. This section...
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Statistics. 1065.602 Section 1065.602 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.602 Statistics. (a) Overview. This section...
Code of Federal Regulations, 2013 CFR
2013-07-01
... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Statistics. 1065.602 Section 1065.602 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.602 Statistics. (a) Overview. This section...
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Statistics. 1065.602 Section 1065.602 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.602 Statistics. (a) Overview. This section...
Statistical Power in Meta-Analysis
ERIC Educational Resources Information Center
Liu, Jin
2015-01-01
Statistical power is important in a meta-analysis study, although few studies have examined the performance of simulated power in meta-analysis. The purpose of this study is to inform researchers about statistical power estimation on two sample mean difference test under different situations: (1) the discrepancy between the analytical power and…
Application of Statistics in Engineering Technology Programs
ERIC Educational Resources Information Center
Zhan, Wei; Fink, Rainer; Fang, Alex
2010-01-01
Statistics is a critical tool for robustness analysis, measurement system error analysis, test data analysis, probabilistic risk assessment, and many other fields in the engineering world. Traditionally, however, statistics is not extensively used in undergraduate engineering technology (ET) programs, resulting in a major disconnect from industry…
Teaching Social Statistics with Simulated Data.
ERIC Educational Resources Information Center
Halley, Fred S.
1991-01-01
Suggests using simulated data to teach students about the nature and use of statistical tests and measures. Observes that simulated data contains built-in pure relationships with no poor response rates or coding or sampling errors. Recommends suitable software. Includes information on using data sets, demonstrating statistical principles, and…
Multidimensional Visual Statistical Learning
ERIC Educational Resources Information Center
Turk-Browne, Nicholas B.; Isola, Phillip J.; Scholl, Brian J.; Treat, Teresa A.
2008-01-01
Recent studies of visual statistical learning (VSL) have demonstrated that statistical regularities in sequences of visual stimuli can be automatically extracted, even without intent or awareness. Despite much work on this topic, however, several fundamental questions remain about the nature of VSL. In particular, previous experiments have not…
Explorations in Statistics: Regression
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2011-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This seventh installment of "Explorations in Statistics" explores regression, a technique that estimates the nature of the relationship between two things for which we may only surmise a mechanistic or predictive connection.…
Reform in Statistical Education
ERIC Educational Resources Information Center
Huck, Schuyler W.
2007-01-01
Two questions are considered in this article: (a) What should professionals in school psychology do in an effort to stay current with developments in applied statistics? (b) What should they do with their existing knowledge to move from surface understanding of statistics to deep understanding? Written for school psychologists who have completed…
Demonstrating Poisson Statistics.
ERIC Educational Resources Information Center
Vetterling, William T.
1980-01-01
Describes an apparatus that offers a very lucid demonstration of Poisson statistics as applied to electrical currents, and the manner in which such statistics account for shot noise when applied to macroscopic currents. The experiment described is intended for undergraduate physics students. (HM)
Statistical Summaries: Public Institutions.
ERIC Educational Resources Information Center
Virginia State Council of Higher Education, Richmond.
This document, presents a statistical portrait of the Virginia's 17 public higher education institutions. Data provided include: enrollment figures (broken down in categories such as sex, residency, full- and part-time status, residence, ethnicity, age, and level of postsecondary education); FTE figures; admissions statistics (such as number…
ERIC Educational Resources Information Center
Huizingh, Eelko K. R. E.
2007-01-01
Accessibly written and easy to use, "Applied Statistics Using SPSS" is an all-in-one self-study guide to SPSS and do-it-yourself guide to statistics. What is unique about Eelko Huizingh's approach is that this book is based around the needs of undergraduate students embarking on their own research project, and its self-help style is designed to…
ERIC Educational Resources Information Center
Council of Ontario Universities, Toronto.
Summary statistics on application and registration patterns of applicants wishing to pursue full-time study in first-year places in Ontario universities (for the fall of 1987) are given. Data on registrations were received indirectly from the universities as part of their annual submission of USIS/UAR enrollment data to Statistics Canada and MCU.…
Introduction to Statistical Physics
NASA Astrophysics Data System (ADS)
Casquilho, João Paulo; Ivo Cortez Teixeira, Paulo
2014-12-01
Preface; 1. Random walks; 2. Review of thermodynamics; 3. The postulates of statistical physics. Thermodynamic equilibrium; 4. Statistical thermodynamics – developments and applications; 5. The classical ideal gas; 6. The quantum ideal gas; 7. Magnetism; 8. The Ising model; 9. Liquid crystals; 10. Phase transitions and critical phenomena; 11. Irreversible processes; Appendixes; Index.
Deconstructing Statistical Analysis
ERIC Educational Resources Information Center
Snell, Joel
2014-01-01
Using a very complex statistical analysis and research method for the sake of enhancing the prestige of an article or making a new product or service legitimate needs to be monitored and questioned for accuracy. 1) The more complicated the statistical analysis, and research the fewer the number of learned readers can understand it. This adds a…
ERIC Educational Resources Information Center
Hodgson, Ted; Andersen, Lyle; Robison-Cox, Jim; Jones, Clain
2004-01-01
Water quality experiments, especially the use of macroinvertebrates as indicators of water quality, offer an ideal context for connecting statistics and science. In the STAR program for secondary students and teachers, water quality experiments were also used as a context for teaching statistics. In this article, we trace one activity that uses…
Understanding Undergraduate Statistical Anxiety
ERIC Educational Resources Information Center
McKim, Courtney
2014-01-01
The purpose of this study was to understand undergraduate students' views of statistics. Results reveal that students with less anxiety have a higher interest in statistics and also believe in their ability to perform well in the course. Also students who have a more positive attitude about the class tend to have a higher belief in their…
Explorations in Statistics: Correlation
ERIC Educational Resources Information Center
Curran-Everett, Douglas
2010-01-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This sixth installment of "Explorations in Statistics" explores correlation, a familiar technique that estimates the magnitude of a straight-line relationship between two variables. Correlation is meaningful only when the…
The ENSEMBLES Statistical Downscaling Portal
NASA Astrophysics Data System (ADS)
Cofino, Antonio S.; San-Martín, Daniel; Gutiérrez, Jose M.
2010-05-01
The demand for high-resolution seasonal and ACC predictions is continuously increasing due to the multiple end-user applications in a variety of sectors (hydrology, agronomy, energy, etc.) which require regional meteorological inputs. To fill the gap between the coarse-resolution grids used by global weather models and the regional needs of applications, a number of statistical downscaling techniques have been proposed. Statistical downscaling is a complex multi-disciplinary problem which requires a cascade of different scientific tools to access and process different sources of data, from GCM outputs to local observations and to run complex statistical algorithms. Thus, an end-to-end approach is needed in order to link the outputs of the ensemble prediction systems to a range of impact applications. To accomplish this task in an interactive and user-friendly form, a Web portal has been developed within the European ENSEMBLES project, integrating the necessary tools and providing the appropriate technology for distributed data access and computing. In this form, users can obtain their downscaled data testing and validating different statistical methods (from the categories weather typing, regression or weather generators) in a transparent form, not worrying about the details of the downscaling techniques and the data formats and access.
Multivariate statistical analysis of environmental monitoring data
Ross, D.L.
1997-11-01
EPA requires statistical procedures to determine whether soil or ground water adjacent to or below waste units is contaminated. These statistical procedures are often based on comparisons between two sets of data: one representing background conditions, and one representing site conditions. Since statistical requirements were originally promulgated in the 1980s, EPA has made several improvements and modifications. There are, however, problems which remain. One problem is that the regulations do not require a minimum probability that contaminated sites will be correctly identified. Another problems is that the effect of testing several correlated constituents on the probable outcome of the statistical tests has not been quantified. Results from computer simulations to determine power functions for realistic monitoring situations are presented here. Power functions for two different statistical procedures: the Student`s t-test, and the multivariate Hotelling`s T{sup 2} test, are compared. The comparisons indicate that the multivariate test is often more powerful when the tests are applied with significance levels to control the probability of falsely identifying clean sites as contaminated. This program could also be used to verify that statistical procedures achieve some minimum power standard at a regulated waste unit.
LED champing: statistically blessed?
Wang, Zhuo
2015-06-10
LED champing (smart mixing of individual LEDs to match the desired color and lumens) and color mixing strategies have been widely used to maintain the color consistency of light engines. Light engines with champed LEDs can easily achieve the color consistency of a couple MacAdam steps with widely distributed LEDs to begin with. From a statistical point of view, the distributions for the color coordinates and the flux after champing are studied. The related statistical parameters are derived, which facilitate process improvements such as Six Sigma and are instrumental to statistical quality control for mass productions. PMID:26192863
Employer Learning and Statistical Discrimination. National Longitudinal Surveys Discussion Paper.
ERIC Educational Resources Information Center
Altonji, Joseph G.; Pierret, Charles R.
The relationship between employer learning and statistical discrimination was explored through a statistical analysis that included a test for statistical discrimination or "rational" stereotyping in environments where agents learn over time. The test is used to study the working hypothesis that, because firms have only limited information about…
Kuhn, T.; Gullett, J. M.; Nguyen, P.; Boutzoukas, A. E.; Ford, A.; Colon-Perez, L. M.; Triplett, W.; Carney, P.R.; Mareci, T. H.; Price, C. C.; Bauer, R. M.
2015-01-01
Introduction This study examined the reliability of high angular resolution diffusion tensor imaging (HARDI) data collected on a single individual across several sessions using the same scanner. Methods HARDI data was acquired for one healthy adult male at the same time of day on ten separate days across a one-month period. Environmental factors (e.g. temperature) were controlled across scanning sessions. Tract Based Spatial Statistics (TBSS) was used to assess session-to-session variability in measures of diffusion, fractional anisotropy (FA) and mean diffusivity (MD). To address reliability within specific structures of the medial temporal lobe (MTL; the focus of an ongoing investigation), probabilistic tractography segmented the Entorhinal cortex (ERc) based on connections with Hippocampus (HC), Perirhinal (PRc) and Parahippocampal (PHc) cortices. Streamline tractography generated edge weight (EW) metrics for the aforementioned ERc connections and, as comparison regions, connections between left and right rostral and caudal anterior cingulate cortex (ACC). Coefficients of variation (CoV) were derived for the surface area and volumes of these ERc connectivity-defined regions (CDR) and for EW across all ten scans, expecting that scan-to-scan reliability would yield low CoVs. Results TBSS revealed no significant variation in FA or MD across scanning sessions. Probabilistic tractography successfully reproduced histologically-verified adjacent medial temporal lobe circuits. Tractography-derived metrics displayed larger ranges of scanner-to-scanner variability. Connections involving HC displayed greater variability than metrics of connection between other investigated regions. Conclusions By confirming the test retest reliability of HARDI data acquisition, support for the validity of significant results derived from diffusion data can be obtained. PMID:26189060
Kuhn, T; Gullett, J M; Nguyen, P; Boutzoukas, A E; Ford, A; Colon-Perez, L M; Triplett, W; Carney, P R; Mareci, T H; Price, C C; Bauer, R M
2016-06-01
This study examined the reliability of high angular resolution diffusion tensor imaging (HARDI) data collected on a single individual across several sessions using the same scanner. HARDI data was acquired for one healthy adult male at the same time of day on ten separate days across a one-month period. Environmental factors (e.g. temperature) were controlled across scanning sessions. Tract Based Spatial Statistics (TBSS) was used to assess session-to-session variability in measures of diffusion, fractional anisotropy (FA) and mean diffusivity (MD). To address reliability within specific structures of the medial temporal lobe (MTL; the focus of an ongoing investigation), probabilistic tractography segmented the Entorhinal cortex (ERc) based on connections with Hippocampus (HC), Perirhinal (PRc) and Parahippocampal (PHc) cortices. Streamline tractography generated edge weight (EW) metrics for the aforementioned ERc connections and, as comparison regions, connections between left and right rostral and caudal anterior cingulate cortex (ACC). Coefficients of variation (CoV) were derived for the surface area and volumes of these ERc connectivity-defined regions (CDR) and for EW across all ten scans, expecting that scan-to-scan reliability would yield low CoVs. TBSS revealed no significant variation in FA or MD across scanning sessions. Probabilistic tractography successfully reproduced histologically-verified adjacent medial temporal lobe circuits. Tractography-derived metrics displayed larger ranges of scanner-to-scanner variability. Connections involving HC displayed greater variability than metrics of connection between other investigated regions. By confirming the test retest reliability of HARDI data acquisition, support for the validity of significant results derived from diffusion data can be obtained.
Statistical Analysis Techniques for Small Sample Sizes
NASA Technical Reports Server (NTRS)
Navard, S. E.
1984-01-01
The small sample sizes problem which is encountered when dealing with analysis of space-flight data is examined. Because of such a amount of data available, careful analyses are essential to extract the maximum amount of information with acceptable accuracy. Statistical analysis of small samples is described. The background material necessary for understanding statistical hypothesis testing is outlined and the various tests which can be done on small samples are explained. Emphasis is on the underlying assumptions of each test and on considerations needed to choose the most appropriate test for a given type of analysis.
Implicit and explicit contributions to statistical learning
Batterink, Laura J.; Reber, Paul J.; Neville, Helen J.; Paller, Ken A.
2015-01-01
Statistical learning allows learners to detect regularities in the environment and appears to emerge automatically as a consequence of experience. Statistical learning paradigms bear many similarities to those of artificial grammar learning and other types of implicit learning. However, whether learning effects in statistical learning tasks are driven by implicit knowledge has not been thoroughly examined. The present study addressed this gap by examining the role of implicit and explicit knowledge within the context of a typical auditory statistical learning paradigm. Learners were exposed to a continuous stream of repeating nonsense words. Learning was tested (a) directly via a forced-choice recognition test combined with a remember/know procedure and (b) indirectly through a novel reaction time (RT) test. Behavior and brain potentials revealed statistical learning effects with both tests. On the recognition test, accurate responses were associated with subjective feelings of stronger recollection, and learned nonsense words relative to nonword foils elicited an enhanced late positive potential indicative of explicit knowledge. On the RT test, both RTs and P300 amplitudes differed as a function of syllable position, reflecting facilitation attributable to statistical learning. Explicit stimulus recognition did not correlate with RT or P300 effects on the RT test. These results provide evidence that explicit knowledge is accrued during statistical learning, while bringing out the possibility that dissociable implicit representations are acquired in parallel. The commonly used recognition measure primarily reflects explicit knowledge, and thus may underestimate the total amount of knowledge produced by statistical learning. Indirect measures may be more sensitive indices of learning, capturing knowledge above and beyond what is reflected by recognition accuracy. PMID:26034344
NASA Astrophysics Data System (ADS)
Richfield, Jon; bookfeller
2016-07-01
In reply to Ralph Kenna and Pádraig Mac Carron's feature article “Maths meets myths” in which they describe how they are using techniques from statistical physics to characterize the societies depicted in ancient Icelandic sagas.
... facts and statistics here include brain and central nervous system tumors (including spinal cord, pituitary and pineal gland ... U.S. living with a primary brain and central nervous system tumor. This year, nearly 17,000 people will ...
Titanic: A Statistical Exploration.
ERIC Educational Resources Information Center
Takis, Sandra L.
1999-01-01
Uses the available data about the Titanic's passengers to interest students in exploring categorical data and the chi-square distribution. Describes activities incorporated into a statistics class and gives additional resources for collecting information about the Titanic. (ASK)
... and Statistics Recommend on Facebook Tweet Share Compartir Plague in the United States Plague was first introduced ... per year in the United States: 1900-2012. Plague Worldwide Plague epidemics have occurred in Africa, Asia, ...
Cooperative Learning in Statistics.
ERIC Educational Resources Information Center
Keeler, Carolyn M.; And Others
1994-01-01
Formal use of cooperative learning techniques proved effective in improving student performance and retention in a freshman level statistics course. Lectures interspersed with group activities proved effective in increasing conceptual understanding and overall class performance. (11 references) (Author)
Purposeful Statistical Investigations
ERIC Educational Resources Information Center
Day, Lorraine
2014-01-01
Lorraine Day provides us with a great range of statistical investigations using various resources such as maths300 and TinkerPlots. Each of the investigations link mathematics to students' lives and provide engaging and meaningful contexts for mathematical inquiry.
Tuberculosis Data and Statistics
... Organization Chart Advisory Groups Federal TB Task Force Data and Statistics Language: English Español (Spanish) Recommend on ... United States publication. PDF [6 MB] Interactive TB Data Tool Online Tuberculosis Information System (OTIS) OTIS is ...
Understanding Solar Flare Statistics
NASA Astrophysics Data System (ADS)
Wheatland, M. S.
2005-12-01
A review is presented of work aimed at understanding solar flare statistics, with emphasis on the well known flare power-law size distribution. Although avalanche models are perhaps the favoured model to describe flare statistics, their physical basis is unclear, and they are divorced from developing ideas in large-scale reconnection theory. An alternative model, aimed at reconciling large-scale reconnection models with solar flare statistics, is revisited. The solar flare waiting-time distribution has also attracted recent attention. Observed waiting-time distributions are described, together with what they might tell us about the flare phenomenon. Finally, a practical application of flare statistics to flare prediction is described in detail, including the results of a year of automated (web-based) predictions from the method.
Oakland, J.S.
1986-01-01
Addressing the increasing importance for firms to have a thorough knowledge of statistically based quality control procedures, this book presents the fundamentals of statistical process control (SPC) in a non-mathematical, practical way. It provides real-life examples and data drawn from a wide variety of industries. The foundations of good quality management and process control, and control of conformance and consistency during production are given. Offers clear guidance to those who wish to understand and implement modern SPC techniques.
NASA Astrophysics Data System (ADS)
Kardar, Mehran
2006-06-01
While many scientists are familiar with fractals, fewer are familiar with the concepts of scale-invariance and universality which underly the ubiquity of their shapes. These properties may emerge from the collective behaviour of simple fundamental constituents, and are studied using statistical field theories. Based on lectures for a course in statistical mechanics taught by Professor Kardar at Massachusetts Institute of Technology, this textbook demonstrates how such theories are formulated and studied. Perturbation theory, exact solutions, renormalization groups, and other tools are employed to demonstrate the emergence of scale invariance and universality, and the non-equilibrium dynamics of interfaces and directed paths in random media are discussed. Ideal for advanced graduate courses in statistical physics, it contains an integrated set of problems, with solutions to selected problems at the end of the book. A complete set of solutions is available to lecturers on a password protected website at www.cambridge.org/9780521873413. Based on lecture notes from a course on Statistical Mechanics taught by the author at MIT Contains 65 exercises, with solutions to selected problems Features a thorough introduction to the methods of Statistical Field theory Ideal for graduate courses in Statistical Physics
Statistical Physics of Particles
NASA Astrophysics Data System (ADS)
Kardar, Mehran
2006-06-01
Statistical physics has its origins in attempts to describe the thermal properties of matter in terms of its constituent particles, and has played a fundamental role in the development of quantum mechanics. Based on lectures for a course in statistical mechanics taught by Professor Kardar at Massachusetts Institute of Technology, this textbook introduces the central concepts and tools of statistical physics. It contains a chapter on probability and related issues such as the central limit theorem and information theory, and covers interacting particles, with an extensive description of the van der Waals equation and its derivation by mean field approximation. It also contains an integrated set of problems, with solutions to selected problems at the end of the book. It will be invaluable for graduate and advanced undergraduate courses in statistical physics. A complete set of solutions is available to lecturers on a password protected website at www.cambridge.org/9780521873420. Based on lecture notes from a course on Statistical Mechanics taught by the author at MIT Contains 89 exercises, with solutions to selected problems Contains chapters on probability and interacting particles Ideal for graduate courses in Statistical Mechanics
Statistical Physics of Fracture
Alava, Mikko; Nukala, Phani K; Zapperi, Stefano
2006-05-01
Disorder and long-range interactions are two of the key components that make material failure an interesting playfield for the application of statistical mechanics. The cornerstone in this respect has been lattice models of the fracture in which a network of elastic beams, bonds, or electrical fuses with random failure thresholds are subject to an increasing external load. These models describe on a qualitative level the failure processes of real, brittle, or quasi-brittle materials. This has been particularly important in solving the classical engineering problems of material strength: the size dependence of maximum stress and its sample-to-sample statistical fluctuations. At the same time, lattice models pose many new fundamental questions in statistical physics, such as the relation between fracture and phase transitions. Experimental results point out to the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances in computer power have enabled considerable progress in the understanding of such models. Among these partly still controversial issues, are the scaling and size-effects in material strength and accumulated damage, the statistics of avalanches or bursts of microfailures, and the morphology of the crack surface. Here we present an overview of the results obtained with lattice models for fracture, highlighting the relations with statistical physics theories and more conventional fracture mechanics approaches.
Helping Alleviate Statistical Anxiety with Computer Aided Statistical Classes
ERIC Educational Resources Information Center
Stickels, John W.; Dobbs, Rhonda R.
2007-01-01
This study, Helping Alleviate Statistical Anxiety with Computer Aided Statistics Classes, investigated whether undergraduate students' anxiety about statistics changed when statistics is taught using computers compared to the traditional method. Two groups of students were questioned concerning their anxiety about statistics. One group was taught…
Suite versus composite statistics
Balsillie, J.H.; Tanner, W.F.
1999-01-01
Suite and composite methodologies, two statistically valid approaches for producing statistical descriptive measures, are investigated for sample groups representing a probability distribution where, in addition, each sample is probability distribution. Suite and composite means (first moment measures) are always equivalent. Composite standard deviations (second moment measures) are always larger than suite standard deviations. Suite and composite values for higher moment measures have more complex relationships. Very seldom, however, are they equivalent, and they normally yield statistically significant but different results. Multiple samples are preferable to single samples (including composites) because they permit the investigator to examine sample-to-sample variability. These and other relationships for suite and composite probability distribution analyses are investigated and reported using granulometric data.
Perception in statistical graphics
NASA Astrophysics Data System (ADS)
VanderPlas, Susan Ruth
There has been quite a bit of research on statistical graphics and visualization, generally focused on new types of graphics, new software to create graphics, interactivity, and usability studies. Our ability to interpret and use statistical graphics hinges on the interface between the graph itself and the brain that perceives and interprets it, and there is substantially less research on the interplay between graph, eye, brain, and mind than is sufficient to understand the nature of these relationships. The goal of the work presented here is to further explore the interplay between a static graph, the translation of that graph from paper to mental representation (the journey from eye to brain), and the mental processes that operate on that graph once it is transferred into memory (mind). Understanding the perception of statistical graphics should allow researchers to create more effective graphs which produce fewer distortions and viewer errors while reducing the cognitive load necessary to understand the information presented in the graph. Taken together, these experiments should lay a foundation for exploring the perception of statistical graphics. There has been considerable research into the accuracy of numerical judgments viewers make from graphs, and these studies are useful, but it is more effective to understand how errors in these judgments occur so that the root cause of the error can be addressed directly. Understanding how visual reasoning relates to the ability to make judgments from graphs allows us to tailor graphics to particular target audiences. In addition, understanding the hierarchy of salient features in statistical graphics allows us to clearly communicate the important message from data or statistical models by constructing graphics which are designed specifically for the perceptual system.
NASA Astrophysics Data System (ADS)
Inomata, Akira
1997-03-01
To understand possible physical consequences of quantum deformation, we investigate statistical behaviors of a quon gas. The quon is an object which obeys the minimally deformed commutator (or q-mutator): a a† - q a†a=1 with -1≤ q≤ 1. Although q=1 and q=-1 appear to correspond respectively to boson and fermion statistics, it is not easy to create a gas which unifies the boson gas and the fermion gas. We present a model which is able to interpolates between the two limits. The quon gas shows the Bose-Einstein condensation near the Boson limit in two dimensions.
Measuring Statistics Anxiety: Cross-Country Validity of the Statistical Anxiety Scale (SAS)
ERIC Educational Resources Information Center
Chiesi, Francesca; Primi, Caterina; Carmona, Jose
2011-01-01
The aim of the research was to test the psychometric properties of the Italian version of the Vigil-Colet et al.'s Statistical Anxiety Scale (SAS), taking into account evidences based on (a) internal structure (factorial structure and cross-country invariance) and (b) relationships to other variables (the statistics anxiety's nomological network).…
Statistical insight: a review.
Vardell, Emily; Garcia-Barcena, Yanira
2012-01-01
Statistical Insight is a database that offers the ability to search across multiple sources of data, including the federal government, private organizations, research centers, and international intergovernmental organizations in one search. Two sample searches on the same topic, a basic and an advanced, were conducted to evaluate the database.
Statistical Reasoning over Lunch
ERIC Educational Resources Information Center
Selmer, Sarah J.; Bolyard, Johnna J.; Rye, James A.
2011-01-01
Students in the 21st century are exposed daily to a staggering amount of numerically infused media. In this era of abundant numeric data, students must be able to engage in sound statistical reasoning when making life decisions after exposure to varied information. The context of nutrition can be used to engage upper elementary and middle school…
Selected Outdoor Recreation Statistics.
ERIC Educational Resources Information Center
Bureau of Outdoor Recreation (Dept. of Interior), Washington, DC.
In this recreational information report, 96 tables are compiled from Bureau of Outdoor Recreation programs and surveys, other governmental agencies, and private sources. Eight sections comprise the document: (1) The Bureau of Outdoor Recreation, (2) Federal Assistance to Recreation, (3) Recreation Surveys for Planning, (4) Selected Statistics of…
Statistics for Learning Genetics
ERIC Educational Resources Information Center
Charles, Abigail Sheena
2012-01-01
This study investigated the knowledge and skills that biology students may need to help them understand statistics/mathematics as it applies to genetics. The data are based on analyses of current representative genetics texts, practicing genetics professors' perspectives, and more directly, students' perceptions of, and performance in,…
Spitball Scatterplots in Statistics
ERIC Educational Resources Information Center
Wagaman, John C.
2012-01-01
This paper describes an active learning idea that I have used in my applied statistics class as a first lesson in correlation and regression. Students propel spitballs from various standing distances from the target and use the recorded data to determine if the spitball accuracy is associated with standing distance and review the algebra of lines…
Geopositional Statistical Methods
NASA Technical Reports Server (NTRS)
Ross, Kenton
2006-01-01
RMSE based methods distort circular error estimates (up to 50% overestimation). The empirical approach is the only statistically unbiased estimator offered. Ager modification to Shultz approach is nearly unbiased, but cumbersome. All methods hover around 20% uncertainty (@ 95% confidence) for low geopositional bias error estimates. This requires careful consideration in assessment of higher accuracy products.
ERIC Educational Resources Information Center
Akram, Muhammad; Siddiqui, Asim Jamal; Yasmeen, Farah
2004-01-01
In order to learn the concept of statistical techniques one needs to run real experiments that generate reliable data. In practice, the data from some well-defined process or system is very costly and time consuming. It is difficult to run real experiments during the teaching period in the university. To overcome these difficulties, statisticians…
Education Statistics Quarterly, 2003.
ERIC Educational Resources Information Center
Marenus, Barbara; Burns, Shelley; Fowler, William; Greene, Wilma; Knepper, Paula; Kolstad, Andrew; McMillen Seastrom, Marilyn; Scott, Leslie
2003-01-01
This publication provides a comprehensive overview of work done across all parts of the National Center for Education Statistics (NCES). Each issue contains short publications, summaries, and descriptions that cover all NCES publications and data products released in a 3-month period. Each issue also contains a message from the NCES on a timely…
Analogies for Understanding Statistics
ERIC Educational Resources Information Center
Hocquette, Jean-Francois
2004-01-01
This article describes a simple way to explain the limitations of statistics to scientists and students to avoid the publication of misleading conclusions. Biologists examine their results extremely critically and carefully choose the appropriate analytic methods depending on their scientific objectives. However, no such close attention is usually…