摘要：In 2004, Murray et al. reviewed methodological developments in the design and analysis of group-randomized trials (GRTs). We have highlighted the developments of the past 13 years in design with a companion article to focus on developments in analysis. As a pair, these articles update the 2004 review. We have discussed developments in the topics of the earlier review (e.g., clustering, matching, and individually randomized group-treatment trials) and in new topics, including constrained randomization and a range of randomized designs that are alternatives to the standard parallel-arm GRT. These include the stepped-wedge GRT, the pseudocluster randomized trial, and the network-randomized GRT, which, like the parallel-arm GRT, require clustering to be accounted for in both their design and analysis. A group-randomized trial (GRT) is a randomized controlled trial in which the unit of randomization is a group, and outcome measurements are obtained for members of the group. 1 Also called a cluster-randomized trial or community trial, 2–5 a GRT is the best comparative design available if the intervention operates at a group level, manipulates the physical or social environment, cannot be delivered to individual members of the group without substantial risk of contamination across study arms, or if there are other circumstances that warrant the design, such as a desire for herd immunity or a need to estimate both the direct and indirect intervention effects in studies of infectious diseases. 1–5 In GRTs, outcomes on members of the same group are likely to be more similar to each other than to outcomes on members from other groups. 1 Such clustering must be accounted for in the design of GRTs to avoid underpowering the study, and it must be accounted for in the analysis to avoid underestimated SEs and inflated type I error for the intervention effect. 1–5 In 2004, Murray et al. 6 published a review of methodological developments in the design and analysis of GRTs. In the 13 years since, there have been many developments in both areas. We highlight developments in both areas in a 2-part series of articles. In this article (part 1), we focus on developments in design. In the second article (part 2), we focus on developments in analysis. 7 (The glossary of terms is available as a supplement to the online version of this article at http://www.ajph.org .) As a pair, these articles update the 2004 review. With both articles, we provide a broad and comprehensive review to guide readers to seek out appropriate materials for their own circumstances.
