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, the hierarchy (1) encompasses study designs whose purpose is to estimate an intervention's effect on educational outcomes; (2) recognizes that many designs, including less rigorous impact studies, can play a valuable role in an overall research agenda; and (3) is intended as a statement of general principles, and does not try to address all contingencies that may affect a study's ability to produce valid results. The hierarchy is based on the best scientific evidence about which study designs are most likely to produce valid estimates of an intervention's true effect. It is also broadly consistent with the standards of evidence used by federal agencies and other authoritative organizations across a number of policy areas and contexts. [Additional support for this document was provided by the Jerry Lee Foundation.]