Evidence-appraisal glossary
Risk of Bias
A judgment about whether flaws in how a study was designed, run, or reported could have pushed its results away from the truth. It asks not whether a study is biased, but how much we should worry that it might be.
Also called: study limitations.
Risk of bias focuses on internal validity: features like how patients were assigned to groups, whether people were blinded, and whether every planned outcome was reported. Reviewers rate each concern separately rather than adding up a single quality score, because one serious flaw can undermine an otherwise careful study. Structured tools such as RoB 2 and ROBINS-I turn these judgments into a consistent, transparent process instead of a gut feeling.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.