Evidence-appraisal glossary
Pre-registration
Pre-registration means publicly recording a study's hypotheses, outcomes, and analysis plan in a time-stamped registry before data are collected or examined. It locks in what researchers said they would test, so readers can check whether the published paper matches the original plan rather than a story shaped after seeing the results.
Also called: preregistration, trial registration, prospective registration.
What it is. Pre-registration is a public, time-stamped commitment, filed in a registry such as ClinicalTrials.gov, the ISRCTN registry, or the OSF, that states a study's research question, primary and secondary outcomes, sample size, and statistical analysis plan before any data are gathered. Prospective registration of trials became a condition of publication in major journals to combat publication bias and selective reporting.
How to use it when reading a study. Look for a registration number and open the record. Compare the pre-specified primary outcome against the outcome the paper emphasizes: a switch (outcome switching) is a red flag for cherry-picking. Check whether the reported analysis matches the registered plan, and whether registration was prospective (before enrollment) or retrospective. Note that pre-registration constrains, but does not eliminate, flexibility, since a vague plan can still be gamed. Its presence and fidelity are markers of credibility, not proof that the results are correct.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.