Validity of Three IRT Models for Measuring and Controlling Extreme and Midpoint Response Styles.

Response styles, the general tendency to use certain categories of rating scales over others, are a threat to the reliability and validity of self-report measures. The mixed partial credit model, the multidimensional nominal response model, and the item response tree model are three widely used models for measuring extreme and midpoint response styles and correcting their effects. This research aimed to examine and compare their validity by fitting them to empirical data and correlating the content-related factors and the response style-related factors in these models to extraneous criteria. The results showed that the content factors yielded by these models were moderately related to the content criterion and not related to the response style criteria. The response style factors were moderately related to the response style criteria and weakly related to the content criterion. Simultaneous analysis of more than one scale could improve their validity for measuring response styles. These findings indicate that the three models could control and measure extreme and midpoint response styles, though the validity of the mPCM for measuring response styles was not good in some cases. Overall, the multidimensional nominal response model performed slightly better than the other two models.