Which statement should be included in the statistical plan to describe interim analysis timing?

• A. A description of the statistical methods to be employed
• B. The description of the statistical methods to be employed, including timing of any planned interim analysis
• C. The budget for data management
• D. The monitoring plan

Answer: (B)

Interim analysis timing must be pre-specified in the statistical plan. The plan should lay out not only the statistical methods to be used but also when interim looks will occur and what criteria will guide any potential stopping decisions. This predefinition preserves trial integrity by preventing data-driven looks, helps control the overall type I error through an explicit alpha-spending or stopping-rule approach, and communicates clearly to all stakeholders when the data will be reviewed.

Describing methods alone misses the timing aspect, which is essential for maintaining statistical validity. A budget focuses on resources and is not about analysis timing, and a separate monitoring plan does not replace the need to specify ahead of time when interim analyses will happen within the statistical framework.