National Institute of Health Research


  • Abstract

    A brief summary of the study and its results. It should tell you what the study tried to show, how the researchers went about it, and what they found.

  • Adverse event

    An unfavourable outcome that occurs during or after the use of a drug or other intervention, but is not necessarily caused by it.

  • Arm

    Refers to a group of participants allocated to a particular treatment. In a randomised controlled trial, allocation to different arms is determined by the randomisation procedure. Many controlled trials have two arms, a group of participants assigned to an experimental intervention (sometimes called the treatment arm) and a group of participants assigned to a control (the control arm). Trials may have more than two arms.

  • Attrition

    The loss of participants during the course of a study. Also called ‘loss to follow up’.


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