Implications of Type of Metric On Regression Assessment

An investigation was conducted to determine if different types of metrics would affect indexing of regression following a summer vacation. Students with learning disabilities and mild mental disabilities from three elementary schools were assessed before and after a summer vacation in math and spelling using grade-level curriculum-based measurement (CBM) materials. Results indicated that the type of metric used, raw score or z-score, affected indexing of regression: Students appeared to have regressed when raw scores were analyzed but appeared not to have regressed when z-scores were analyzed. Possible explanations for this difference and suggested recommendations are discussed.