A comparison of the added value of subscores across two subscore augmentation methods

Testing organizations are faced with increasing demand to provide subscores in addition to the total test score. However, psychometricians argue that most subscores do not have added value to be worth reporting. To have added value, subscores need to meet a number of criteria: they should be reliable, distinctive, and distinct from each other and from the total score. In this study, the quality of subscores from two subscore augmentation models (Wainer and Yen) were compared in terms of distinctness and variability. The reliabilities of the Wainer-augmented subscores were also examined. The models were applied to a high-stakes English language proficiency test in Iran. The results of the study showed that Yen better satisfied subscore distinctness while Wainer best preserved variability and had high-reliability subscores. In other words, Yen-augmented subscores had lower correlations while Wainer-augmented subscores better discriminated examinees with different ability levels. Thus, none of the examined models of subscoring satisfied all criteria. The results of the study are discussed and suggestions for future research are provided.