Calibration of invariant item parameters in a continuous item response model using the extended lisrel measurement submodel

This article attempts to study the utility of Sorbom's (1974) Confirmatory Factor Analysis (CFA) with mean structures model, to estimate invariant difficulty and discrimination item parameters on a personality scale. A set of items from the Social Worry Scale, belonging to the ''Anxious Thoughts Inventory'' (Wells, 1994) are administered using a continuous response format. The general sample is split into two groups according to gender and an invariant CFA model with mean structures is fitted simultaneously in both groups. The results suggest that both the format and the model may be of interest for personality scales.