Assessing clinical significance using robust normative comparisons

Clinical significance determines whether an intervention makes a real difference in the everyday life of a client. One of the most recommended approaches for conducting group-level analyses of clinical significance is to evaluate whether the treated clinical group is equivalent to a normal comparison group (normative comparisons). The purpose of this study was to demonstrate the analytical and practical power of assessing clinical significance using normative comparisons that are robust to violations of normality and homogeneity of variance assumptions. Six datasets were gleaned from published intervention studies for depression. We found that normative comparisons using a robust Schuirmann-Yuen test determined equivalency for 11% fewer clinical samples compared to original normative comparisons that use a Schuirmann test of equivalence. We recommend that researchers conducting normative comparisons utilize the Schuirmann-Yuen procedure as it provides the most reliable method available for determining if a treated clinical group is equivalent to a normative comparison group.