Evidence-appraisal glossary
Certainty of Evidence
Certainty of evidence is a rating of how much confidence you can place in an estimate of effect, commonly graded as high, moderate, low, or very low. It reflects how likely further research is to change the conclusion, not how large or how significant the effect is.
Also called: quality of evidence, confidence in the evidence, GRADE rating.
A body of evidence starts with a certainty level set by study design and is then rated down for problems such as risk of bias, inconsistency, indirectness, imprecision, and publication bias, or occasionally rated up for features like a large effect. The result tells a reader how firmly a recommendation can rest on the underlying studies. Because it is a property of the whole evidence base for one outcome, a striking p-value from a single flawed trial can still sit atop low certainty.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.