Clinical Research Glossary

arm arm


A group of participants in a research study who all receive the same study treatment.

Example of arm in a sentence

If a study has two arms, one group will receive one study treatment while a second group will receive a different study treatment such as a placebo or the standard of care.

More Info

Studies that compare two or more study treatments divide participants into separate arms to compare the effects of the different treatments.

Other info to think about when joining a study

You may see the term “arm” in the consent form or when the study team is explaining the research study to you. They may mention that there will be different arms in the study you are joining. You may be randomized to one arm or another

You can ask how many arms will be in a study. If there are arms, you can clarify how participants will be assigned to receive the different study treatments.

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