The increasing ability of social policy researchers to conduct randomized controlled trials (RCTs) at low cost could revolutionize the field of performance-based government. RCTs are widely judged to be the most credible method of evaluating whether a social program is effective, overcoming the demonstrated inability of other, more common methods…

This document contains a narrative overview of the hierarchy, followed by a one-page graphic summary. The purpose of the hierarchy is to help agency/program officials assess which study designs are capable of producing scientifically-valid evidence on the effectiveness of a STEM education project or practice ("intervention"). More specifically,…