Evidence: What is it and does it matter?

Objective:Everyone talks about implementing evidence-based policies and programs but what is “evidence”, how do we find evidence, and what if there is no evidence to be found? We will review sources of evidence, compare different approaches to rating evidence, and discuss use of evidence in efforts to improve community health. Study Design: We conducted a qualitative review of ten web sites that provide ratings of evidence of effectiveness for policies and programs that address the multiple determinants of health to determine how each site defined and assigned different ratings of evidence. Analysis: We examined each site to see whether and how they addressed the many dimensions to consider when assessing the effectiveness of a given policy or program. For example: How many studies were reviewed? How strong is the demonstrated effect? Have results been replicated? Has causality been established? Principal Findings: Among the variety of potential sources of “evidence”, the term “evidence-based” is widely used but with inconsistent definitions. Standards for evidence differ across disciplines. Assessing evidence and assigning ratings requires careful attention to the quality and quantity of findings from intervention research. Conclusion: Concise, reliable summaries of evidence of effectiveness can help inform policy and program selection and funding decisions. Knowledge of ratings of effectiveness should be balanced with local needs, resources, and culture when deciding which policies and programs to implement.