The contention that interpretation of a student's performance on a criterion referenced test should be independent of the performance of his classmates is challenged. The Mastery Learning Test Model, which was developed for analyzing criterion referenced test data, is described. An estimate of the proportion of students in an instructional group which has achieved the referent objective is usable as a prior probability in interpreting individual responses. Considering instructional group performance enhances estimates of individual performance. Correlational data from a set of test items and a representative population of students are used to estimate the required item parameters. (Author)