The purpose of this ITEMS module is to provide an introduction to differential item functioning (DIF) analysis using mixture item response models. The mixture item response models for DIF analysis involve comparing item profiles across latent groups, instead of manifest groups. First, an overview of DIF analysis based on latent groups, called…

This article examines how psychometric models based on certain assumptions have come to be used counterproductively by many practitioners in ways that limit the kinds of conclusions that can be made. The general problem of the context's influence on performance is discussed, and some implications are drawn. (SLD)

This instructional module discusses the one-, two-, and three-parameter logistic item response theory (IRT) models. Mathematical formulas are given for each model and they are compared, with figures illustrating the effects of changing parameters. A single data set is used to demonstrate the effects of changing parameter values. (SLD)

Several available summaries of research on coaching for the Scholastic Aptitude Test (SAT) are described, and their principal findings are discussed. Several additional studies are reviewed, and their findings are related to the summaries. Overall, the effects of coaching may be less than many students suppose. (SLD)