Hi, there,

I am running a simulation study using item parameters estimated from the partial credit model (model item + item*step), and hoping to get some clarification on the exact parameterization used in ConQuest.

1. What are the parameters that I should use to compute the probability that person i receives a score k on item j? My current output produces estimates for item, item*step, and thresholds.

2. What's the right formula (i.e., exact parameterization) to compute such a probability?

I am also curious about the interpretation of the ConQuest parameters. For example, what does each of the three (item, item*step, threshold) mean? How the ConQuest parameters can be mapped (or transformed) into the usual PCM parameterization with step difficulty? One thing I sort of figured out from the manual is that the threshold is the theta level at which a person has 50% chance scoring at this category or higher. Is this correct? Does it mean that the threshold is sort of like the graded response model parameterization?

Many thanks!

Ying