Levels of Evidence

Levels of Evidence

We recognize that evidence exists in different forms. PolicyForResults.org relies on three levels of evidence:

· Rigorous statistical evidence refers to the most scientifically defensible evidence, which comes through statistical evaluations with control groups, randomly assigned participation, and/or tests of statistical significance. Research of this sort is usually not available, particularly in the fields related to children and family policy. In addition, it is important to exercise caution when interpreting and generalizing findings from this sort of research to entire populations. True random assignment is ethically prohibited in many cases and this limitation must be recognized when interpreting the findings of quasi-experimental studies.

· Program evaluation and emerging evidence refers to evidence that is derived from state studies, policy analysis, the evaluations of specific programs and research or extrapolations from related fields.

· Practice-based evidence refers to evidence that enjoys broad consensus from practitioners. Practice-based evidence of success and experience can provide compelling evidence, as can research providing strong, but not conclusive, statistical evidence.