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

整群随机实验被认为是确定教育治疗和干预措施影响的金标准。必须作出的最重要的设计决定之一是确定学生样本和正在研究的分组(例如教室或教师或学校)的大小，以便估计预期效果的力量。目前，设计成仅检测具有足够功率的治疗的主要效果的整群随机试验是很常见的。这些研究错过了对治疗可能对谁产生影响(调解)以及治疗有效的条件(缓和)进行有效评估的能力。这项研究将通过开发多水平调节和调节测试的功率公式和软件，以及两者的结合来促进我们对整群随机试验的理解。本项目将包括三个部分：1)。在群组随机试验中开发新的公式来估计检测多水平缓和、中介、缓和中介和中介缓和的统计能力；通过模拟对公式进行评估和验证；3)。在现有的两个软件程序OPTIME Design Plus和PowerUp！中实现这些公式。该项目将编写使用新分析的培训材料，并开发和举办讲习班，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.