Which trial design randomizes participants to two or more arms, each arm receiving a different treatment?

• A. Parallel Group Design
• B. Crossover Design
• C. Factorial Designs
• D. Multicenter Trials

Answer: (A)

The main idea being tested is how participants are allocated to treatment arms in a randomized trial. When participants are randomized into two or more arms and each arm receives a different treatment, with individuals remaining in their assigned arm for the study, that is a parallel group design. This setup lets you compare outcomes between the distinct treatment groups at the same time, with each participant contributing data to only one treatment condition.

In contrast, a crossover design has participants receive multiple treatments in a sequence, separated by washout periods, so the same person experiences several treatments rather than being assigned to a single arm. Factorial designs study multiple factors and their interactions, producing arms that are combinations of treatments or factor levels rather than simply assigning each participant to one distinct treatment. Multicenter trials refer to the study being conducted at multiple sites, not the structure of treatment arms.

So, the described scenario fits a parallel group design.