Normative comparisons for the evaluation of clinical significance.

Normative comparisons are a procedure for evaluating the clinical significance of therapeutic interventions. This procedure, consisting of comparing data on treated individuals with that of normative individuals, is described, and a step-by-step statistical methodology for conducting normative comparisons in the context of treatment-outcome research is presented. Four examples of the methodology are outlined in detail. Attention is paid to potential theoretical, statistical, and methodological challenges to the implementation of normative comparisons, as well as to the advantages of normative comparisons in providing evidence for the beneficial gains of treatment.