A Simple and Effective Method to Test the Dimensionality Axiom of the Rasch Model

A simple method is introduced to test the dimensionality axiom in the Rasch model. The method consists of a suitable partitioning of the data set. This partitioning is based on the responses to some of the items being investigated. The items used for this purpose are called the external criterion items. data are presented indicating the effectiveness of the method in instances where the traditional test procedures fail.