An item response model with single peaked item characteristic curves: The PARELLA model

In this paper an item response model (the PARELLA model) designed specifically for the measurement of attitudes and preferences will be introduced. In contrast with the item response models currently used (e.g. the Rasch model and, the two and three parameter logistic model) the item characteristic curve is single peaked instead of monotonically increasing. The model and its properties will be introduced. After this the consequences of these properties for the item writing stage, the evaluation of the concordance of data and model, and the applicability of the model will be discussed. The paper is finished with an example concerning the measurement of change in the attitude in the car-environment issue.