Questionnaires that include items eliciting count responses are becoming increasingly common in psychology. This study proposes methodological techniques to overcome some of the challenges associated with analyzing multivariate item response data that exhibit zero inflation, maximum inflation, and heaping at preferred digits. The modeling…

Local dependence (LD) refers to the violation of the local independence assumption of most item response models. Statistics that indicate LD between a pair of items on a test or questionnaire that is being fitted with an item response model can play a useful diagnostic role in applications of item response theory. In this article, a new score test…

This article examines the affect of misfit on methods to minimize the inaccuracy of the Item Response Theory (IRT). Three of the most commonly used IRT models were fit in this simulation. (RB)

Results of a simulation study imply that S X squared may be a useful tool in detecting the misfit of one item contained in an otherwise well-fitted test, lending additional support to the utility of the index for use with dichotomous item response theory models. (SLD)

The purpose of this paper is to introduce a new method for fitting item response theory models with the latent population distribution estimated from the data using splines. A spline-based density estimation system provides a flexible alternative to existing procedures that use a normal distribution, or a different functional form, for the…