What is the research question? Estimands explained

Although many papers of medical research report on a treatment effect, it is not always clear what is exactly meant by that effect. An estimand is a precise definition of a treatment effect and includes 5 attributes: population, treatment, (outcome) variable, intercurrent events, and summary measure. In this paper, we discuss how the estimand framework helps to align different phases of studies of medical treatments, from research objectives to design, conduct, analysis, and reporting of results.