Over the past 15 years, we have seen an increase in the use of cluster randomized trials (CRTs) to test the efficacy of educational interventions. These studies are often designed with the goal of determining whether a program works, or answering the what works question. Recently, the goals of these studies expanded to include for whom and under what conditions an intervention is effective. In this study, we examine the capacity of a set of CRTs to provide rigorous evidence about for whom and under what conditions an intervention is effective. The findings suggest that studies are more likely to be designed with the capacity to detect potentially meaningful individual-level moderator effects, for example, gender, than cluster-level moderator effects, for example, school type.

在过去的15年中，我们已经看到使用丛集随机试验（CRT）来测试教育干预措施的功效的情况有所增加。这些研究通常旨在确定程序是否有效或回答什么有效的问题。最近，这些研究的目标扩展到包括对谁有效以及在什么条件下有效的干预措施。在这项研究中，我们检查了一组CRT的能力，以提供关于干预对谁有效以及在什么条件下有效的严格证据。研究结果表明，与集群水平的主持人影响（例如学校类型）相比，研究更有可能具有检测潜在有意义的个人级别的主持人影响（例如性别）的能力。