Validating a Distractor-Driven Geometry Test Using a Generalized Diagnostic Classification Model

Abstract

This chapter uses a generalized diagnostic classification model (GDCM) to provide validity evidence for a test measuring student misconceptions in middle school geometry. The test is an example of a “distractor-driven” test that includes selected-response questions with systematically written incorrect response options; scoring the test involves tracking which specific response options students select for each item. The test is intended to provide teachers with an efficient means of obtaining instructionally useful information about their students’ reasoning, including whether students may be reasoning with common misconceptions that could interfere with their learning. The GDCM framework provides a way to formally evaluate whether student response patterns on the test correspond to the proposed test score interpretations. The analyses illustrate how graphical and numerical GDCM results can be used to validate intended score uses and guide future test development. The discussion considers both the strengths and limitations of applying the GDCM framework to this type of distractor-driven test.