Evidence-appraisal glossary
Information bias
Information bias is systematic error that arises when an exposure, outcome, or other variable is measured or classified inaccurately. Unlike random measurement noise, it distorts results in a consistent direction.
Also called: measurement bias, observation bias.
Information bias covers any flaw in how data are collected or recorded, including recall bias, interviewer bias, and misclassification of disease status. It is often split into non-differential error, which usually pulls estimates toward no effect, and differential error, which can push them in either direction. A common misreading is to assume all measurement error is harmless averaging out; error that differs between the groups being compared does not average out and can create or hide an association.
Read the full Reading the Evidence blog.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.