## What is/are Wedge Trials?

Wedge Trials - CONCLUSION About half of recently published stepped-wedge trials reached their planned sample size indicating that recruitment is also a major problem in these trials.^{[1]}We encountered unanticipated methodological challenges with this trial design, which can provide valuable learning for future research and inform the trial design of future international stepped-wedge trials.

^{[2]}OBJECTIVES There is substantial variation in the design of stepped wedge trials.

^{[3]}Background/Aims: Power and sample size calculation formulas for stepped-wedge trials with two levels (subjects within clusters) are available.

^{[4]}Interpretation of such guidance for cluster-randomized trials and stepped-wedge trials, which commonly evaluate complex non-therapeutic interventions such as knowledge translation, public health, or health service delivery interventions, can pose challenges to researchers and regulators.

^{[5]}In this paper, we consider stepped-wedge trials that accommodate treatment effect heterogeneity across clusters, implementation periods during which no data are collected, or both treatment effect heterogeneity and implementation periods.

^{[6]}Permutation tests are useful in stepped-wedge trials to provide robust statistical tests of intervention-effect estimates.

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