Evidence-appraisal glossary
Estimand
A precise statement of exactly what a trial is trying to measure: which treatment effect, in which patients, on what outcome, and how complications during the study are handled. It is the question, settled before you compute an answer.
Also called: target of estimation.
An estimand pins down details that were once left vague, especially how to treat intercurrent events like stopping the drug or needing rescue medication. Two analyses of the same trial can produce different numbers simply because they target different estimands, so naming it stops people arguing past one another. Fixing the estimand in advance also disciplines the analysis and narrows the room for outcome switching.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.