This study investigated the Type I error rate and power of the multivariate extension of the S - [chi][squared] statistic using unidimensional and multidimensional item response theory (UIRT and MIRT, respectively) models as well as full-information bifactor (FI-bifactor) models through simulation. Manipulated factors included test length, sample…

This article describes the results of a simulation study to investigate the impact of missing data on the detection of differential item functioning (DIF). Specifically, it investigates how four methods for dealing with missing data (listwise deletion, zero imputation, two-way imputation, response function imputation) interact with two methods of…

In recent years there has been an increasing international interest in fine-grained diagnostic inferences on multiple skills for formative purposes. A successful provision of such inferences that support meaningful instructional decision-making requires (a) careful diagnostic assessment design coupled with (b) empirical support for the structure…

This article reviews research on differential item functioning (DIF) in language testing conducted primarily between 1990 and 2005 with an eye toward providing methodological guidelines for developing, conducting, and disseminating research in this area. The article contains a synthesis of 27 studies with respect to five essential sets of…

In most large-scale assessments of student achievement, several broad content domains are tested. Because more items are needed to cover the content domains than can be presented in the limited testing time to each individual student, multiple test forms or booklets are utilized to distribute the items to the students. The construction of an…