A Nondiagnostic Assessment for Diagnostic Purposes: Q-Matrix Validation and Item-Based Model Fit Evaluation for the TIMSS 2011 Assessment

Large-scale assessments are generally designed for summative purposes to compare achievement among participating countries. However, these nondiagnostic assessments have also been adapted in the context of cognitive diagnostic assessment for diagnostic purposes. Following the large amount of investments in these assessments, it would be cost-effective to draw finer-grained inferences about the attribute mastery. Nonetheless, the correctness of attribute specifications in the Q-matrix has not been verified, despite being designed by domain experts. Furthermore, the underlying process of TIMSS (Trends in International Mathematics and Science Study) assessment is unknown as it was not developed for diagnostic purposes. Thus, this study suggests an initial validating attribute specifications in the Q-matrix and thereafter defining specific reduced or saturated models for each item. In doing so, the two analyses were validated across 20 countries that were selected randomly for TIMSS 2011 data. Results show that attribute specifications can differ from expert opinions and the underlying model for each item can vary.