In a crossover design, what is a key benefit for treatment comparisons?

• A. It reduces the need for randomization
• B. Each subject serves as their own control for treatment comparisons
• C. It eliminates the placebo effect completely
• D. It requires fewer participants but cannot assess carryover effects

Answer: (B)

In a crossover design, each participant receives all treatments in different periods, so treatment comparisons are made within the same person. This means every individual acts as their own control, which cancels much of the between-person variability—like genetics, baseline health, and lifestyle—that often clouds differences between treatments. By reducing this variability, the estimate of the treatment effect becomes more precise, and you can achieve adequate power with fewer participants when the condition is reversible and a proper washout period minimizes carryover.

Remember, randomization is still used to determine the order of treatments to limit sequencing bias. The design does not eliminate the placebo effect, and carryover effects can be addressed with washouts and appropriate analysis rather than being deemed unassessable.