The How Do We Know Initiative
How will I know how strong the evidence is for my intervention?
The evidence-based approach encourages state and district leaders to examine the strength of the evidence in making decisions. Selecting evidence-based practices supports the use of limited resources-people, time, and money-in ways that are more likely to have an impact. The strongest evidence comes from well designed and well implemented randomized control experimental studies. However, plenty of other research, including quasi-experimental designs and correlational research, can provide credible evidence.
The federal Every Student Succeeds Act (ESSA) provides one useful way of thinking about the spectrum of evidence quality. In the law, evidence ranges from randomized control trial experiments, which provide strong evidence, to research conducted on a program based on a strong rationale or theory of action. Districts should seek out interventions with the strongest evidence, while at the same time considering whether and how the research reflects its students and context. That is, seek out the strongest evidence that reflects your context. The figure below illustrates how districts might locate the quality of evidence along the strength and context continuums.
Tier 1 — Strong Evidence1: Supported by one or more well designed and well implemented randomized control experimental studies.
Tier 2 — Moderate Evidence: Supported by one or more well designed and well implemented quasi-experimental studies.
Tier 3 — Promising Evidence: Supported by one or more well designed and well implemented correlational studies (with statistical controls for selection bias).
Tier 4 — Demonstrates a Rationale: Practices that have a well defined logic model or theory of action, are supported by research, and have some effort underway by an SEA, LEA, or outside research organization to determine their effectiveness.
1 More information about these levels can be found in the U.S. Department of Education's guidance: Using Evidence to Strengthen Educational Investments