Conducted simulations to explore methods for comparing bivariate distributions corresponding to two independent groups, all of which are based on Tukey's "depth," a generalization of the notion of ranks to multivariate data. Discusses steps needed to control Type I error. (SLD)

Used Johnson's transformation (N. Johnson, 1978) with approximate test statistics to test the homogeneity of simple linear regression slopes in the presence of nonnormality and Type I, Type II or complete heteroscedasticity. Computer simulations show that the proposed techniques can control Type I error under various circumstances. (SLD)

Examined the degree of variation in the accuracy of classifying student performance proficiency-level scores with changes in the number of proficiency levels and the measurement accuracy. Simulation results show the limitations of interpretability of single indexes that are intended to represent classification accuracy. Suggests ways to estimate…

Proposed a method for extending the Bollen-Stine bootstrap model (K. Bollen and R. Stine, 1992) fit to structural equation models with missing data. Developed a Statistical Analysis System macro program to implement this procedure, and assessed its usefulness in a simulation. The new method yielded model rejection rates close to the nominal 5%…

Used computer simulation methods to examine the sensitivity of model fit criteria to misspecification of the first-level error structure in two-level models of change and to examine the impact of misspecification estimates on the variance parameters, estimates of the fixed effects, and tests of the fixed effects. Discusses problems caused by…

Studied the multiplicative gamma model for reading speed originally proposed by G. Rasch (1960/1980). Simulation results suggest that Rasch's extended multiplicative gamma model, if reasonably descriptive, allows for a simple and elegant analysis of test and item response times. (SLD)

Proposed two new indices to detect answer copying on a multiple choice test and conducted a simulation study to investigate the usefulness of both indexes. Discusses conditions under which the proposed indexes can be useful. (SLD)

Illustrates how commonly available structural equation modeling programs can be used to conduct some basic matrix manipulations and generate multivariate normal data with given means and positive definite covariance matrix. Demonstrates the outlined procedure. (SLD)

Examined two methods for fitting models of intrinsic dynamics to intraindividual variability data by testing these techniques' behavior in equations through simulation studies. Among the main results is the demonstration that a local linear approximation of derivatives can accurately recover the parameters of a simulated linear oscillator, with…

Studied planned incomplete data designs for the purpose of substantially reducing the amount of data required for multitrait-multimethod models. Simulations studied the effectiveness of Listwise Deletion, Pairwise Deletion, and the expectation maximization (EM) algorithm. Results indicate that EM is generally precise and efficient. (SLD)

Developed a hierarchal measurement model that enables researchers to measure a latent trait variable and model the error variance corresponding to multiple levels. This Rasch hierarchical measurement model results when a Rasch item response theory model and a one-way analysis of variance with random effects are combined. Two simulated data sets…

Proposed a new asymptotic formula for estimating the sampling variance of a correlation coefficient corrected for unreliability and range restriction. A Monte Carlo simulation study of the new formula results in several positive conclusions about the new approach. (SLD)

Analyzed the relations between two continuous response models intended for typical response items: the linear congeneric model and Samejima's continuous response model (CRM). Illustrated the relations described using an empirical example and assessed the relations through a simulation study. (SLD)

Proposed a maximum likelihood procedure for combining the standardized mean differences based on a noncentral-t-distribution and developed an EM algorithm. Simulation results favor the proposed procedure over the existing normal theory maximum likelihood procedure and the commonly used generalized least squares procedure. (SLD)

Investigated the effect of item parameter drift on ability estimates under item response theory, simulating item response data for two testing occasions for the two-parameter logistic model under several crossed conditions. Results show that item parameter drift under the simulated conditions had a small effect on ability estimates. (SLD)