The step wedge design is one of the recent advances in study designs. But how does it work? It seems to use a complex set of steps. But there is one simple principle behind step-wedge design: Don’t leave anyone behind. At the end, everyone receives an intervention or at least part of it.
The key ethical limitation in RCTs being the withholding of intervention from control groups, the SWD addresses this major limitation. It also creates the opportunity to study the dose-response relationship between the intervention and its outcomes, i.e. whether those participants who received higher dose of the intervention also have higher level of outcomes and vice versa.
SWD provides an excellent option for real world implementation trials. A researcher can deliver the intervention for the study groups sequentially. There is no need for control group but a ‘waiting’ group only. It looks this new design is addressing our key challenges with RCTs.