Effects of different weighting schemes on selecting the optimal number of observations in multivariate-multifacet generalizability designs are studied when cost constraints are imposed. Comparison of four schemes through simulation indicates that all four produce similar optimal values and that reliability should be similar. (SLD)

Rasch model total-fit statistics and between-item fit statistics were compared for their ability to detect measurement disturbances through the use of simulated data. Results indicate that the between-fit statistic appears more sensitive to systematic measurement disturbances and the total-fit statistic is more sensitive to random measurement…

Six stepwise multiple-comparison procedures for repeated-measures means were compared for their overall familywise rates of Type I error when multisample sphericity and multivariate normality were not satisfied. Robust stepwise procedures were identified by Keselman, Keselman, and Shaffer (1991) with respect to three definitions of power. (SLD)

An extension to the partial credit model, the linear partial credit model, is considered under the assumption of a certain linear decomposition of the item x category parameters into basic parameters. A conditional maximum likelihood algorithm for estimating basic parameters is presented and illustrated with simulation and an empirical study. (SLD)

The suggestion that the IDIOSCAL model be fitted by the TUCKALS2 algorithm for three-way components analysis is examined. The claim that resulting coordinate matrices will be identical is supported when the data matrices are semidefinite. Counterexamples for indefinite matrices are also constructed. (SLD)

Methods of testing relatively complete (distributional) models of internal psychological processes are described. It is shown that there is a sufficient condition for additive models to imply this property of the likelihood ratio. Also discussed are the examination of hazard rate functions of component processes and change in cumulative…

Comparisons of the Wilcoxon test, Friedman test, and repeated-measures analysis of variance (ANOVA) on ranks in a computer simulation show that the Friedman test performs like the sign test whereas the ANOVA performs like the Wilcoxon test. Classification of these tests in introductory statistics textbooks should be revised. (SLD)

A review of the literature indicates that the two best procedures for testing variances are one that was proposed by O'Brien (1981) and another that was proposed by Brown and Forsythe (1974). An examination of these procedures for a variety of populations confirms their robustness and indicates how optimal power can usually be obtained. (SLD)

The effect of reducing the number of score groups in the matching criterion of the Mantel-Haenszel procedure when screening for differential item functioning was investigated with a simulated data set. Results suggest that more than modest reductions cannot be recommended when ability distributions of reference and focal groups differ. (SLD)

The statistical analysis of processing tree models is advanced by showing how the parameters of estimation and hypothesis testing, based on the likelihood functions, can be accomplished by adapting the expectation-maximization (EM) algorithm. The adaptation makes it easy to program a personal computer to accomplish the stages of statistical…

Given a Masters partial credit item with n known step difficulties, conditions are stated for the existence of a set of (locally) independent Rasch binary items such that their raw score and the partial credit raw score have identical probability density functions. (Author/SLD)

A statistical power algorithm based on the Fisher Z method is developed for cutoff-based random clinical trials and the single cutoff-point (regression-discontinuity) design that has no randomization. This article quantifies power and sample size estimates for various levels of power and cutoff-based assignment. (Author/SLD)

One of the issues facing educational research workers today is the determination of the similarities and differences between countries and cultures in the factors that influence educational outcomes. The author of this article proposes a new approach to this problem. Usually when countries are compared, the complete student samples are taken into…

Introducing students to measurement concepts poses unique instructional challenges; yet, the importance of measurement issues for all data collection scenarios (e.g., the classroom, individual clients, sporting events) requires that students understand the value of basic measurement procedures. Illustrating the basic measurement topics of…

Not infrequently, investigators assume that reliability for groups is greater than reliability for persons, or that the error variance for groups is less than that for persons. Using generalizability theory, it is shown that this "conventional wisdom" is not necessarily true. Examples are provided from the course-evaluation and the…