Control arm

In a clinical trial, the control arm is the group of participants that does not receive the therapy being studied (investigational therapy). This control arm is compared to the group that receives the investigational therapy, to see if the investigational therapy works and is safe.

The comparison of the investigational therapy arm against the control arm defines what the results of the trial actually mean and the context for how the results can be used in clinical practice.

Sourced From
National Cancer Institute (NCI) Dictionary of Cancer Terms