Which design assigns a sequence of two or more treatments to the same participant, allowing them to serve as their own control?

Which design assigns a sequence of two or more treatments to the same participant, allowing them to serve as their own control?

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

Answer: (B)

Two or more treatments are given to the same participant in sequence, allowing them to serve as their own control. In a crossover design, every participant receives each treatment in a randomized order, often with a washout period between treatments to minimize carryover. This within-subject approach reduces variability from differences between participants, improving statistical efficiency and requiring fewer participants to detect a treatment effect. This is different from a parallel group design, where each participant is assigned to only one treatment for the entire study, so comparisons are between different individuals. Factorial designs explore multiple factors and their interactions across groups, not necessarily by the same participant receiving all treatments. Multicenter trials refer to conducting the study at several sites, which affects logistics and generalizability but not the within-subject treatment sequence.

Two or more treatments are given to the same participant in sequence, allowing them to serve as their own control. In a crossover design, every participant receives each treatment in a randomized order, often with a washout period between treatments to minimize carryover. This within-subject approach reduces variability from differences between participants, improving statistical efficiency and requiring fewer participants to detect a treatment effect.

This is different from a parallel group design, where each participant is assigned to only one treatment for the entire study, so comparisons are between different individuals. Factorial designs explore multiple factors and their interactions across groups, not necessarily by the same participant receiving all treatments. Multicenter trials refer to conducting the study at several sites, which affects logistics and generalizability but not the within-subject treatment sequence.