Evidence-appraisal glossary
Stepped-wedge trial
A cluster randomized design in which every cluster starts in the control condition and then crosses over to the intervention at a randomly assigned point in a staggered sequence, until all clusters have received it.
Also called: stepped wedge design, stepped-wedge cluster randomized trial.
Stepped-wedge trials suit situations where an intervention is expected to help, so withholding it from anyone for the whole study is hard to justify, and where a program can only be rolled out in stages. The staggered timing means each cluster contributes both control and intervention data, with the order of crossover assigned at random. Because the switch to the intervention is tied to the passage of calendar time, the analysis has to separate the treatment effect from underlying time trends and seasonal changes, or the two become confounded.
This is a plain-language methodology definition for reading research. It is general education, not medical advice.