Difficulty, Discrimination, and Information Indices in the Linear Factor Analysis Model for Continuous Item Responses

Abstract

Spearman's factor-analytic model has been proposed as a unidimensional linear item response theory (IRT) model for continuous item responses. This article first proposes a reexpression of the model that leads to a form similar to that of standard IRT models for binary responses and discusses the item indices of difficulty discrimination and information. Next, the extension to the multiple-factor model is considered, and multidimensional counterparts of the item indices are proposed. The interpretation of the proposed measures and their usefulness in personality and attitude measurement are discussed and illustrated by means of two empirical examples.