“…The first consideration when choosing the right model involves the number of item response categories. For polytomous items, variations of the Partial Credit Model (Masters, 1982); Rating Scale Model (Andrich, 1978); Generalized Partial Credit Model (Muraki, 1992(Muraki, , 1997 as well as the GRM (Samejima 1969(Samejima , 1997 are available for ordered responses, and the Nominal Model (Bock, 1972) is appropriate for items with a non-specified response order. We consider the GRM (Samejima, 1997) because it is appropriate to use when item responses are ordered categorical responses.…”