The program can recalibrate with misfitting persons removed and can exclude very low and very high scoring persons from the calibration process. These programs estimate parameters for and test the fit of data to the Dichotomous, Rating Scale, and Partial Credit models. Both programs provide a single difficulty for each item and a single measure for each person. In addition to estimates of difficulty and ability and tests of item and person fit, output includes a variety of graphical displays. The programs also contain editing features which edit out perfect person and item scores, adjust for missing responses, and recode input data into successive integers.
Compilations are available for most micro, mini, and mainframe computers.
The output is designed to be interpretable by classroom teachers. Person ability and item difficulty estimates are automatically transformed from logits to a metric like the ones with which teachers are already familiar. The program is available for a nominal fee from Geoff Masters, University of Melbourne. The information is very detailed and usually provides insight into the causes of misfit. It is dimensioned for 100 items and an unlimited number of persons, but these dimensions can be altered.