A prespecified subgroup analysis is one that is planned and documented before any examination of the data, preferably in the study protocol. This analysis includes specification of the end point, the baseline characteristic, and the statistical method used to test for an interaction.

What is a pre-specified analysis?

Pre-specified analysis is subgroup analysis that was planned during the initial experiment design stage, before looking at any data.

How do you write a subgroup analysis?

Subgroup analysis is one way of finding out. It's a type of analysis done by breaking down study samples into subsets of participants based on a shared characteristic. The goal is to explore differences in how people respond to an intervention.