Comment & Questions:
1. the matrix Q’ in P. 553 seems incorrect.
2. The algorithm is similar to iteration procedure in DIF study. I’m thinking the consequence of implement purification procedure to obtain correct Q-matrix.
3. In future study, how to calibrate a newly added item to the tests in which a subset of items whose attributes are known? It is an interesting topic.
4. It is a difficutly paper for me and I'm not really understand it.