To further understand the properties of data-generation algorithms for multivariate, nonnormal data, two Monte Carlo simulation studies comparing the Vale and Maurelli method and the Headrick fifth-order polynomial method were implemented. Combinations of skewness and kurtosis found in four published articles were run and attention was…

This article extends recent research on item parameter drift by investigating the robustness properties of basic unidimensional IRT models. Specifically, the article explores whether it is possible to advocate the consistent choice of one model over another based on its robustness properties under drift. On the one hand, it is shown that the…

The present study investigates whether the Early Development Instrument (Offord & Janus, 1999) measures school readiness similarly across different groups of children. We employ ordinal logistic regression to investigate differential item functioning, a method of examining measurement bias. For 40,000 children, our analysis compares groups…

Nonparametric and robust statistics (those using trimmed means and Winsorized variances) were compared for their ability to detect treatment effects in the two-sample case. The use of two specialized tests, designed to be sensitive to treatment effects when data distributions are skewed to the right, is not supported by the analyses. (SLD)