An item response theory analysis of the Questionnaire of God Representations.

The Dutch Questionnaire of God Representations (QGR) was investigated by means of item response theory (IRT) modeling in a clinical (n = 329) and a nonclinical sample (n = 792). Through a graded responsemodel and IRT-based differential functioning techniques, detailed item-level analyses and information about measurement invariance between the clinical and nonclinical sample were obtained. On the basis of the results of the IRT analyses, a shortened version of the QGR (S-QGR) was constructed, consisting of 22 items, which functions in the same way in both the clinical and the nonclinical sample. Results indicated that the QGR consists of strong and reliable scales which are able to differentiate among persons. Psychometric characteristics of the S-QGR were adequate.