Commentary on “Validation Methods for Aggregate-Level Test Scale Linking: A Case Study Mapping School District Test Score Distributions to a Common Scale”

This paper begins by setting the linking methods of Reardon, Kalogrides, and Ho in the broader literature on linking. Trends in the validity data suggest that there may be a conditional bias in the estimates of district means, but the data in the article are not conclusive on this point. Further, the data used in their case study might support the validity of the methods only over a limited range of the ability continuum. Applications of the method are then discussed. Contrary to the title, the application of the linking results is not limited to aggregate-level data. Because the potential application is so broad, further research is needed on issues such as the possibility of conditional bias and the validity of estimates over the full range of possible values. Validity is not a dichotomous concept where validity exists or it does not. The evidence reported by Reardon et al. provides substantial, but incomplete, support for the validity of the linked measures in this case study.