Collaborative Research: Power Analyses for Moderator and Mediator Effects in Cluster Randomized Trials

聚类随机实验被认为是黄金标准，通过它可以确定教育治疗和干预的影响。必须做出的最重要的设计决策之一是确定所研究的学生样本和集群（例如，教室或教师或学校）的大小，以便估计预期效果的功率。目前，通常设计一个集群随机试验来检测具有足够疗效的治疗的主要效果。这些研究错过了能够提供有效的评估，即治疗可能对谁产生影响（调解），以及治疗有效的条件（适度）。本研究将通过开发幂函数公式和软件，进一步加深我们对聚类随机试验的理解，以检验多层次的调节和中介，以及两者的结合。这个项目将有三个组成部分：1)。聚类随机试验中多级调节、中介、被调节-中介和被调节-中介的统计力估计新公式的建立2）. 通过模拟评估和验证公式；3)。在两个现有的软件程序中实现这些公式，优化设计Plus和PowerUp！该项目将编制使用新分析的培训材料，并发展和举办讲习班，以便向外地广泛传播该工具。

Cluster randomized experiments are considered the gold standards by which the impact of educational treatments and interventions can be determined. One of the most important design decisions that must be made is determining the size of the sample of students and the clusters under study (e.g., classrooms or teachers or schools) in order to estimate the power for an anticipated effect. Currently it is common for a cluster randomized trial to be designed to detect only the main effect of a treatment with adequate power. These studies miss out on being able to provide valid assessments of for whom a treatment might have an impact (mediation) and the conditions under which a treatment is effective (moderation). This research study will advance our understanding of cluster randomized trials by developing power formulas and software for tests of multi-level moderation and mediation, as well as the combination of the two.This project will have three components: 1). The development of new formulas for estimating the statistical power to detect multilevel moderation, mediation, moderated-mediation and mediated-moderation in cluster randomized trials; 2). Assess and validate the formulas through simulations; and, 3). Implement the formulas in two existing software programs, Optimal Design Plus and PowerUp!. The project will develop training materials for the use of the new analyses and develop and conduct workshops in order to disseminate the tool widely to the field.