Abstract

Editor Introduction: This chapter takes a polytomous IRT model (Samejima’s normal model for graded responses) and applies it within a factor analytic context. This allows the evaluation of a set of data in an exploratory and confirmatory factor analytic framework. As well as demonstrating an application of a polytomous IRT model, this chapter also shows how such models can be used to evaluate model fit and the dimensionality of a set of data.