stepwedge

Stepwedge is a term used in experimental design, particularly in fields like agriculture, medicine, and manufacturing. It refers to a type of experimental design where one or more factors are systematically varied across different levels, but these levels are not necessarily applied to all experimental units. Instead, the levels of one or more factors are "stepped" or "wedged" across the experimental units in a specific pattern.

The primary purpose of a stepwedge design is often to study the effect of an intervention or treatment over time, especially when it is not feasible to apply the intervention to all units simultaneously. For example, in a healthcare setting, a new protocol might be implemented in different hospital wards sequentially, with each ward serving as a control group for a period before the intervention is introduced. This allows for comparison between wards that have and have not yet received the intervention.

Stepwedge designs can help control for time-dependent confounding factors, as the introduction of the intervention is staggered. This sequential implementation also makes it more practical and cost-effective in many situations compared to a full factorial design or a randomized controlled trial where all units are treated at once. The analysis of data from a stepwedge design typically involves statistical methods that account for the staggered introduction of the intervention and potential clustering of units.