Evidence-appraisal glossary
Survivorship bias
Survivorship bias is a distortion that arises when analysis includes only the subjects, records, or units that made it past some selection point, while those that dropped out, failed, or died are silently missing. Conclusions then reflect the survivors rather than the whole.
Also called: survivor bias, survival bias.
Survivorship bias is a form of selection bias in which the excluded cases are invisible precisely because they did not survive to be observed, such as studying only long-term patients on a therapy while those who stopped early are absent. It routinely makes interventions, funds, or strategies look more successful than they are. The remedy is to ask what has been left out of the sample, not just to analyze what remains.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.