This study evaluated the sensitivity of maximum likelihood (ML)-, generalized least squares (GLS)-, and asymptotic distribution-free (ADF)-based fit indices to model misspecification, under conditions that varied sample size and distribution. The effect of violating assumptions of asymptotic robustness theory also was examined. Standardized root-mean-square residual (SRMR) was the most sensitive index to models with misspecified factor covariance(s), and Tucker-Lewis Index (1973; TLI), Bollen's fit index (1989; BL89), relative noncentrality index (RNI), comparative fit index (CFI), and the MLand GLS-based gamma hat, McDonald's centrality index (1989; Me), and root-mean-square error of approximation (RMSEA) were the most sensitive indices to models with misspecified factor loadings. With ML and GLS methods, we recommend the use of SRMR, supplemented by TLI, BL89, RNI, CFI, gamma hat, Me, or RMSEA (TLI, Me, and RMSEA are less preferable at small sample sizes). With the ADF method, we recommend the use of SRMR, supplemented by TLI, BL89, RNI, or CFI. Finally, most of the ML-based fit indices outperformed those obtained from GLS and ADF and are preferable for evaluating model fit.

Fit indices in covariance structure modeling : Sensitivity to underparameterized model misspecification

Contemporary mate preferences can provide important clues to human reproductive history. Little is known about which characteristics people value in potential mates. Five predictions were made about sex differences in human mate preferences based on evolutionary conceptions of parental investment, sexual selection, human reproductive capacity, and sexual asymmetries regarding certainty of paternity versus maternity. The predictions centered on how each sex valued earning capacity, ambition— industriousness, youth, physical attractiveness, and chastity. Predictions were tested in data from 37 samples drawn from 33 countries located on six continents and five islands (total N = 10,047). For 27 countries, demographic data on actual age at marriage provided a validity check on questionnaire data. Females were found to value cues to resource acquisition in potential mates more highly than males. Characteristics signaling reproductive capacity were valued more by males than by females. These sex differences may reflect different evolutionary selection pressures on human males and females; they provide powerful cross-cultural evidence of current sex differences in reproductive strategies. Discussion focuses on proximate mechanisms underlying mate preferences, consequences for human intrasexual competition, and the limitations of this study.

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Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures

This paper describes the statistical similarities among mediation, confounding, and suppression. Each is quantified by measuring the change in the relationship between an independent and a dependent variable after adding a third variable to the analysis. Mediation and confounding are identical statistically and can be distinguished only on conceptual grounds. Methods to determine the confidence intervals for confounding and suppression effects are proposed based on methods developed for mediated effects. Although the statistical estimation of effects and standard errors is the same, there are important conceptual differences among the three types of effects.

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Equivalence of the Mediation, Confounding and Suppression Effect

Null hypothesis significance testing (NHST) is the dominant statistical approach in biology, although it has many, frequently unappreciated, problems. Most importantly, NHST does not provide us with two crucial pieces of information: (1) the magnitude of an effect of interest, and (2) the precision of the estimate of the magnitude of that effect. All biologists should be ultimately interested in biological importance, which may be assessed using the magnitude of an effect, but not its statistical significance. Therefore, we advocate presentation of measures of the magnitude of effects (i.e. effect size statistics) and their confidence intervals (CIs) in all biological journals. Combined use of an effect size and its CIs enables one to assess the relationships within data more effectively than the use of p values, regardless of statistical significance. In addition, routine presentation of effect sizes will encourage researchers to view their results in the context of previous research and facilitate the incorporation of results into future meta-analysis, which has been increasingly used as the standard method of quantitative review in biology. In this article, we extensively discuss two dimensionless (and thus standardised) classes of effect size statistics: d statistics (standardised mean difference) and r statistics (correlation coefficient), because these can be calculated from almost all study designs and also because their calculations are essential for meta-analysis. However, our focus on these standardised effect size statistics does not mean unstandardised effect size statistics (e.g. mean difference and regression coefficient) are less important. We provide potential solutions for four main technical problems researchers may encounter when calculating effect size and CIs: (1) when covariates exist, (2) when bias in estimating effect size is possible, (3) when data have non-normal error structure and/or variances, and (4) when data are non-independent. Although interpretations of effect sizes are often difficult, we provide some pointers to help researchers. This paper serves both as a beginner’s instruction manual and a stimulus for changing statistical practice for the better in the biological sciences.

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Effect size, confidence interval and statistical significance: a practical guide for biologists.

Decreased bioavailability of vitamin D in obesity

Experimental Design: Procedures for the Behavioral Sciences

Chapter 1. Research Strategies and the Control of Nuisance Variables Chapter 2. Experimental Designs: an Overview Chapter 3. Fundamental Assumptions in Analysis of Variance Chapter 4. Completely Randomized Design Chapter 5. Multiple Comparison Tests Chapter 6. Trend Analysis Chapter 7. General Linear Model Approach to ANOVA Chapter 8. Randomized Block Designs Chapter 9. Completely Randomized Factorial Design with Two Treatments Chapter 10. Completely Randomized Factorial Design with Three or More Treatments and Randomized Block Factorial Design Chapter 11. Hierarchical Designs Chapter 12. Split-Plot Factorial Design: Design with Group-Treatment Confounding Chapter 13. Analysis of Covariance Chapter 14. Latin Square and Related Designs Chapter 15. Confounded Factorial Designs: Designs with Group-Interaction Confounding Chapter 16. Fractional Factorial Designs: Designs with Treatment-Interaction Confounding

Statistical significance is concerned with whether a research result is due to chance or sampling variability; practical significance is concerned with whether the result is useful in the real worl...

Practical Significance: A Concept Whose Time Has Come

Experimental design: Procedures for the behavioral sciences (3rd ed.).

Master Teacher and writer Roger E. Kirk brings two clear goals to the Fifth Edition of STATISTICS: AN INTRODUCTION: to provide a sound introduction to descriptive and inferential statistics and to help students read and understand statistical presentations in their field. Kirk provides guidelines to help you decide when to use various procedures, and how to understand the logic of the procedures. This revision includes a complete update, focusing specifically on increased coverage of effect size and power. Benefits: NEW! Based on reviewer feedback, Kirk has significantly updated this edition, focusing specifically on increased coverage of effect size and power. Kirk covers descriptive and inferential statistics in depth. Other key topics covered include confidence intervals, visual approaches to understanding data such as box plots and confidence interval graphs, and procedures for detecting outliers. Powerful multiple comparison procedures and discussions of printouts from three popular microcomputer statistics packages (JMP, SPSS, and SYSTAT) expose students to these commonly used programs. Students will find that selecting an appropriate statistic is easier with the help of the Selection Guide for descriptive and inferential statistics on the front endpaper. The back endpaper provides a quick reference for important formulas. An extensive glossary of statistical symbols serves as an additional resource for students. The student database in Appendix E provides additional sources of exercises. The database enables students to gain experience drawing random samples and computing statistics using real data. NEW! Greater emphasis is given to visual approaches to aid in understanding data such as box plots and graphs of confidence intervals. NEW! Numerous examples interspersed throughout the text show the way statistical results are presented in scientific publications. NEW! Discussion of probability and selected advanced topi

Roger E. Kirk

Papers

Experimental Design: Procedures for the Behavioral Sciences

Experimental Design: Procedures for the Behavioral Sciences

Practical Significance: A Concept Whose Time Has Come

Experimental design: Procedures for the behavioral sciences (3rd ed.).

Statistics: An Introduction