What is an estimand?

Published

March 21, 2026

What is an estimand?

From the glossary of the ICH E9: estimands addendum:

A precise description of the treatment effect reflecting the clinical question posed by the trial objective. It summarises at a population-level what the outcomes would be in the same patients under different treatment conditions being compared.

Where should I start?

The trainings page is a starting point.

Further, a 3min intro video is available: What is an estimand in a clinical trial: The PIONEER 1 example.

The book from Jiawei Wei, Leslie Meng, Frank Bretz, Feng Chen and Jun Wang (editors) Estimands in Clinical Trials - A Practical Guide (ISBN:978-3-032-02191-5) provides a comprehensive, up-to-date, and practical introduction to the estimand framework and its application in clinical trials.

See also the publications page regarding work from the EIWG. Recently, members of the EIWG have prepared topics on ICH E9(R1) requiring further clarification.