Within-study bias

Systematic displacement of an individual study estimate caused by design, conduct, analysis or selective reporting. Combining estimates can reduce random error without reducing this bias. Bias-adjusted meta-analysis and analyses restricted or stratified by relevant bias domains can assess its impact.

Model study estimates as noisy versions of the target effects plus study-specific biases. External information or sensitivity parameters describe those biases and their uncertainty. Removing an assumed bias without propagating its uncertainty overstates precision; observed study data alone generally do not identify the adjustment.