I want to estimate the scores of 10 students in 4 tests.

The relationship between students to tests is many to many, but

- There are students who have not taken some of the tests — so for these students, it doesn’t make sense to have a sample site for the tests they have not taken

Basically, for every test, the number of students who have taken that test is not always equal to 10.

When I used a nested plate notation, I get a total of 40 parameters, among which many are unused and their estimates are corrupting the (multi-level) hyperprior estimates.

How can I avoid these unused parameters from being estimated by the model?

Ideally, my parameter array would be a 2d list of lists.