INFORMATION FUNCTIONS OF THE GENERALIZED PARTIAL CREDIT MODEL

Abstract

ABSTRACTThe concept of information functions developed for dichotomous item response models is adapted for the partial credit model. The information function is explained in terms of the model parameters and scoring functions. The relationship between the item information function and the expected score function is also discussed. The information function is then used to investigate the effect of collapsing and recoding categories of polytomously‐scored items of the National Assessment of Educational Progress (NAEP). Finally, the NAEP writing items are calibrated and the item and test information is used to discuss desirable properties of polytomous items.item response model polytomous item response model partial credit model information function NAEP