Bao, H., Gotwals, A. W., & Mislevy, R. J. (2006). Assessing local item dependence in building explanation tasks (PADI Technical Report 14). Menlo Park, CA: SRI International.
A common practice in the assessment of science education is to have a shared stimulus followed by a number of questions. In these cases, one might doubt the usual assumption of standard Item Response Theory of local item independence among items that are supposed to measure the same latent proficiency. As an anticipated violation of conditional independence within these item bundles or testlets, such a violation might contribute to the misfit of a unidimensional model; one might consider a unidimensional model that incorporates local dependence. On the other hand, violations of local independence in a unidimensional model might, in some cases, be more satisfactorily solved with a multidimensional model with local independence. Even a multidimensional model with local dependence might be entertained. This report discusses the extension and application of the Item Bundle Model developed by Wilson and Adams (1995) that takes into account multidimensionality and item dependence simultaneously. The use of the measurement model is illustrated in the framework of one of the examples of the Principled Assessment Designs for Inquiry (PADI) Project, namely, the University of Michigan’s BioKIDS 2003 Fall Assessment.