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必须研究的教室、教师或学校样本的大小，以便确定治疗对研究结果的统计显著影响。然而，目前通常的做法是设计一种随机试验，只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）。本研究将通过开发权力公式和软件来提高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。本项目将包括以下三个组成部分：1)开发新的公式来估计集群随机试验中阻止多级调节、中介、被调节-中介和被调节-调节的统计能力；2)通过仿真对公式进行评估和验证；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 classrooms or teachers or schools that must be studied in order to determine a statistically significant effect of the treatment on the outcomes under study. However, 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 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 as follows: 1). development of new formulas for estimating the statistical power to deter 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.