Using Explanatory Item Response Theory Modeling to Investigate Context Effects of Differential Item Functioning for Students With Disabilities

To address whether or not modifications in test administration influence item functioning for students with disabilities on a high-stakes statewide problem-solving assessment, a sample of 868 students (with and without disabilities) from 74 Georgia schools were randomly assigned to one of three testing conditions (resource guide, calculator, or standard administration). The authors describe a conceptual framework for investigating measurement invariance, specifically differential item functioning within the context of assessing students with disabilities. Specifically, we illustrate how the hierarchical generalized linear model, an explanatory model that incorporates item response models into hierarchical models in multilevel settings, can be used to explore issues of measurement invariance traditionally addressed using descriptive item response models, that is, the many-facet Rasch model. Results obtained from the two approaches are reported and discussed.