CUPED

CUPED - Controlled-experiment Using Pre-Existing Data

CUPED (short for Controlled-experiment Using Pre-Existing Data) is a technique which leverages user information from before an experiment to reduce the variance, and increase confidence in experimental metrics. This can help to debias experiments which have meaningful pre-exposure bias (e.g. the groups were randomly different before any treatment was applied).

See more at the Variance Reduction page.