Person Fit in the Rasch Model

Abstract

The idea of whether a person's response pattern is "believable" given his estimated ability is one of the central issues in measurement. This article traces the development of this idea from Thurstone to Rasch. It also presents the rationale behind the development of person analysis in the Rasch model. Finally, it presents data based on simulated response patterns which provide insight into the power and Type I error rates of the Rasch unweighted total and between person fit statistics under a variety of simulated measurement disturbances.