This paper describes the development of a language arts test to assess the consistency of student response patterns and the feasibility of using the test to diagnose students' misconceptions. The studies were part of a project to develop computerized adaptive testing for the language arts with software to diagnose student errors. The domain-referenced test on pronoun usage featured matched pairs of test items. To diagnose errors it was assumed that: (1) a misconception could only lead to an incorrect response; and (2) matched items would get the same incorrect response. The test was administered to three samples of inner-city sixth graders, in groups, and individually with students asked to explain the reasons for their responses. Results indicated that neither students' wrong answer choices nor the rationale for their answers were consistent enough to warrant analyzing student response patterns in the classroom. Student inconsistency in test answering strategies may have important implications for measurement models and theories that assume a systematic and analytic approach to test taking. (BS)