An effectiveness rating is the assessment of the Pathways Clearinghouse, based on the existing evidence from impact studies, of the extent to which a given intervention improves a specific type of outcome. The effectiveness rating is a holistic assessment of whether an intervention is likely to produce favorable results if faithfully replicated with a similar population. An effect size is a standardized measure that allows us to make direct and meaningful comparisons across different outcomes, settings, and interventions. Both the effectiveness rating and the effect size can be compared across studies in the Pathways Clearinghouse. The effect size is the impact found in the available research, and the effectiveness rating is the likelihood that an intervention would produce a similar, favorable effect if implemented again with a similar population and context.