Known beta parameters in IRT model


#1

Dear stan forum users,

I’d like to estimate irt model under the assumption that the item parameters are known and fixed. This is the case that items from an item pool with known item parameters are administered to new test-takers and an ability estimation for every test-taker is needed. How can I introduce known beta parametrs to the stan code instead of estimation them?

thank you for any help!
Krzysiek


#2

Pass them into the data block rather than declaring them in the parameters block.


#3

If you really want to fix them, then doing what @bgoodri suggests will work.

I’m guessing you probably have some estimates of these beta from previous data, so that there’s some residual uncertainty. You could then use that uncertainty to put priors on these beta in the new model. Of you can just take all the data and combine it to run a bigger model.