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

集群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学生样本的大小和研究中的集群（例如，教室或教师或学校），以便估计预期效果的功率。目前，通常的情况是，设计一个群集随机试验，仅检测具有足够把握度的治疗的主要效应。这些研究错过了能够提供有效评估的治疗可能会产生影响（调解）和治疗有效的条件（适度）。本研究将通过开发多水平调节和中介检验的功效公式和软件，以及两者的结合，促进我们对集群随机试验的理解。本项目将包括三个部分：1）.在整群随机试验中，建立了估计检验多水平调节、中介、调节-中介和中介-调节统计功效的新公式; 2）。通过模拟评估和验证公式; 3）。在两个现有的软件程序Optimal Design Plus和PowerUp！中实现公式。该项目将为使用新的分析编制培训材料，并组织和举办讲习班，以便向外地广泛传播这一工具。

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.