The purpose of this paper is to briefly introduce two most common applications of multiple group item response theory (IRT) models, namely detecting differential item functioning (DIF) analysis and nonequivalent group score linking with a simultaneous calibration. We illustrate how to conduct those analyses using the "Stata" item…

The nonequivalent groups anchor test (NEAT) design is often used to scale item parameters from two different test forms. A subset of items, called the anchor items or common items, are administered as part of both test forms. These items are used to adjust the item calibrations for any differences in the ability distributions of the groups taking…

Common items with inconsistent b-parameter estimates may have a serious impact on item response theory (IRT)--based equating results. To find a better way to deal with the outlier common items with inconsistent b-parameters, the current study investigated the comparability of 10 variations of four IRT-based equating methods (i.e., concurrent…

This comprehensive "Handbook" focuses on the most used polytomous item response theory (IRT) models. These models help us understand the interaction between examinees and test questions where the questions have various response categories. The book reviews all of the major models and includes discussions about how and where the models…

A necessary prerequisite to the operational use of item response theory (IRT) in any testing program is the investigation of the feasibility of such an approach. This report presents the results of such research for the Graduate Management Admission Test (GMAT). Despite the fact that GMAT data appear to violate a basic assumption of the…