Conceptualizing changes in behavior in intervention research: The range of possible changes model.

An international movement has focused on identifying evidence-based interventions that were developed to change psychological constructs and that are supported by controlled studies. However, inconsistent findings within individual intervention studies and among multiple studies raise critical problems in interpreting the evidence, and deciding when and whether an intervention is evidence-based. A theoretical and methodological framework (Range of Possible Changes [RPC] Model) is proposed to guide the study of change in intervention research. The authors recommend that future quantitative reviews of the research literature use the RPC Model to conceptualize, examine, and classify the available evidence for interventions. Future research should adopt the RPC Model to both develop theory-driven hypotheses and conduct examinations of the instances in which interventions may or may not change psychological constructs.