Before revision: In the polytomous Rasch "Partial Credit" model (Masters, 1982 ), the probability of the outcome is where is the kth threshold location of item i on a latent continuum, is the location of person n on the same continuum, and is the maximum score for item i.
After revision: In the polytomous Rasch (Andrich, 1978 ), the probability of the outcome is where is the kth threshold location of item i on a latent continuum, is the location of person n on the same continuum, and is the maximum score for item i.