Glossary // Glossary term Technical
Regression to the mean
The statistical tendency for an unusually extreme measurement to be followed by one closer to the average, simply because part of any single measurement is random variation. People often seek help, or enrol in studies, when they feel at their worst, so they are likely to report some improvement later whatever is done. Without a comparison group, improvement after an intervention cannot be separated from this effect. How one could reason about recording a catharsis-like change of state: signals, features, inference and context, baselines, self-report, error costs and ethics, and why every step stays uncertain. Nothing on this site measures anyone. Every public claim on this site with its type, evidence level, confidence, sources and review date, and an appraisal of each reference. How claims are graded, how art is kept apart from evidence, and how to report a problem.Where the site uses it