In a clinical trial, the term “cohort” refers to a subgroup of participants who share common characteristics or have been exposed to similar interventions. For example, in a clinical trial comparing the efficacy of two different drugs, one cohort of participants may receive drug A while another cohort receives drug B.
The term “arm” is used to describe a specific group of participants in a clinical trial who receive the same intervention. For example, in a clinical trial comparing two different drugs, one arm of the trial may receive drug A while another arm receives drug B.
So, the main difference between a cohort and an arm in a clinical trial is that a cohort is a subgroup of participants who share common characteristics or have been exposed to similar interventions, while an arm is a specific group of participants who receive the same intervention.
In a clinical trial, the number of arms is determined by the number of interventions being compared, while the number of participants in each arm is determined by the sample size of the trial and the desired level of statistical power. The choice of the number of arms and the size of each arm will depend on various factors, including the objectives of the trial, the size of the target population, the anticipated treatment effect, the variability of the outcome measures, and the available resources.
Uthando Nethemba 