Title: Unidimensional and Multidimensional IRT Modeling with the mirt package.

 

Abstract: This presentation focuses on unidimensional and multidimensional item response theory (UIRT and MIRT, respectively) models that can be estimated with the mirt (Chalmers, 2012) package in R. In general I will go over: what IRT is, why it exists, and how it relates to other latent variable methods such as factor analysis; several types of IRT models and how these can be generalized to more than one dimension; how to fit UIRT and MIRT models to psychological test data with the mirt package; useful model comparison techniques, computing latent trait scores and item/person fit statistics, plotting item and test probability curves and information functions; and (time permitting) explore some more advanced methods such as multiple group analysis for detecting DIF, user defined prior parameter distributions and starting values, linear parameter constraints, Wald tests, and so on.