A Comparison of Approaches for Improving the Reliability of Objective Level Scores

Abstract

This study is an evaluation of the psychometric issues associated with estimating objective level scores, often referred to as ‘‘subscores.’’ The article begins by introducing the concepts of reliability and validity for subscores from statewide achievement tests. These issues are discussed with reference to popular scaling techniques, classical test theory, and item response theory. Methods for increasing the reliability of subscore estimates that have been suggested in literature are then reviewed. Based on this review, an empirical study comparing some of the more promising procedures was conducted. Test score data from a large statewide testing program were analyzed in this study. The comparison of subscore augmentation approaches found that generally all methods were very successful in dramatically increasing the reliability of subscore estimates. However, this increase was accompanied by near-perfect correlations among the subscore estimates. This finding called into question the validity of the resultant subscores, and therefore the usefulness of the subscore augmentation process. Implications for practice are discussed.