Hello!
I’m working on an item response theory (IRT) application and have a general Stan modeling question about “carrying forward” a posterior distribution from one model into a second model.
Use case: In a typical calibration-and-field-test workflow, we first fit an IRT model to estimate both person parameters (θ) and item parameters (a, b, etc.) on an operational item set. Later, we field-test new items and want to estimate their item parameters using the same person parameter estimates from the first calibration — essentially holding the person parameter posteriors fixed rather than re-estimating them jointly with the new item parameters.
My question: Is there a standard/recommended way in Stan to pass a previously-estimated posterior distribution in as data so that it acts as a fixed (not re-estimated) distribution for those parameters in a second model?