A maximum test in which the test statistic is the more extreme of the Brown-Forsythe and in which O'Brien's test statistics are developed, with estimated Type I error rates and power for all three tests. For study conditions, Type I error rates for the maximum test are near the nominal level. (SLD)

One approach to the analysis of repeated measures data allows researchers to model the covariance structure of their data rather than presume a certain structure, as is the case with conventional univariate and multivariate test statistics. This mixed-model approach, available through SAS PROC MIXED, was compared to a Welch-James type statistic.…

One of the most frequently encountered problems in educational research and evaluation is that of evaluating the effect of a treatment in settings over which the researcher or evaluator has little control. A strong plea is made for use of quasi-experimental designs in these situations and this research provides a method of testing the hypothesis…

The Welch-James procedure may be used to test hypothesis on means, when independent samples from populations with heterogenous variances are available. Summation formulas for the Welch-James procedure are presented for the 2x2 design. Matrix formulas that permit routine application of the procedure to crossed factorial designs are presented.…

Results of using multimethod factor analysis and exploratory factor analysis for the analysis of three multitrait-multimethod matrices are compared. Results suggest that the two methods can give quite different impressions of discriminant validity. In the examples considered, the former procedure tends to support discrimination while the latter…

Probability coverage for eight different confidence intervals (CIs) of measures of effect size (ES) in a two-level repeated measures design was investigated. The CIs and measures of ES differed with regard to whether they used least squares or robust estimates of central tendency and variability, whether the end critical points of the interval…

The approximate degrees of freedom Welch-James (WJ) and Brown-Forsythe (BF) procedures for testing within-subjects effects in multivariate groups by trials repeated measures designs were investigated under departures from covariance homogeneity and normality. Empirical Type I error and power rates were obtained for least-squares estimators and…

This text was written to help the reader acquire a base of knowledge about classical psychometrics and to integrate new ideas into that framework of knowledge. The material is organized into five units: (1) introduction to measurement theory; (2) reliability; (3) validity; (4) item analysis in test development; and (5) test scoring and…

Sampling distributions for ten tests for comparing population variances in a two group design were generated for several combinations of equal and unequal sample sizes, population means, and group variances when distributional forms differed. The ten procedures included: (1) O'Brien's (OB); (2) O'Brien's with adjusted degrees of freedom; (3)…

This paper focuses on the questions which arise as test practitioners monitor score scales derived from latent trait theory. Large scale assessment programs are dynamic and constantly challenge the assumptions and limits of latent trait models. Even though testing programs evolve, test scores must remain reliable indicators of progress.…