The impact of social desirability bias on the EPQ-R item scores: An item response theory analysis

This study assessed the potential influence of social desirability (SD) response bias on the E, N, and P EPQ-R scores at the level of individual items. The study was based on a bidimensional IRT model which was fitted in a large sample. This allowed a detailed analysis of both the internal validities of the items and the content of the items which were most affected by SD. The E items were least affected by SD, but the direction of the impact depended on the type of item. As expected, in the N and P cases the relations obtained were consistently negative, but the strength of the SD impact also depended considerably on the type of item. The P scale was the most problematic in terms of convergent and discriminant validity. 2008 Elsevier Ltd. All rights reserved.