Modifying Conditional Probability in E-step

[smi...@rowan.edu]

Greetings, Phil (and others).

I am interested in modifying the expression for conditional probability in the E-step when calculating the updated r and N values, and I am wondering if this is possible in mirt. My situation is that I have a test with a series of nominal items, followed by a group of dichotomous items (for which I'm using 2pl). I would like the group of dichotomous items to have as much influence during the E-step as each of the individual nominal items. I think I could accomplish this by modifying the conditional probability product such that the terms for the dichotomous items are raised to a power equal to the inverse of the number of items (e.g., raised to the 1/5 if there are 5 dichotomous items). Is this possible in mirt? If it matters, I'm using a unidimensional model.

I've been searching the literature, as well as this group, but I haven't been able to find anything similar to this that treats different items differently when expressing the conditional probability. Thanks so much for any information or advice!

Best,

Trevor