Which design is used to facilitate interim analyses in clinical trials?

• A. Factorial Designs
• B. Group Sequential Designs
• C. Crossover Designs
• D. Fixed-Sample Designs

Answer: (B)

Interim analyses with preplanned stopping rules are built into the group sequential design. This approach lets researchers peek at accumulating data at predefined points and decide, based on predefined boundaries, whether to continue, stop early for efficacy, or stop for futility or safety, all while controlling the overall type I error rate. That ability to plan multiple looks and maintain statistical integrity is what makes group sequential designs the design of choice for facilitating interim analyses.

Factorial designs focus on evaluating multiple factors and their interactions, not on monitoring data partway through a trial. Crossover designs involve the same participants receiving multiple treatments in sequence, which is about within-subject comparisons rather than interim monitoring. Fixed-sample designs collect all data to a single planned endpoint with no interim analyses.