This paper reviews the use of multiple trials, defined as multiple sites or multiple arms in a single evaluation and replications, in evaluating social programs. After defining key terms, the paper discusses the rationales for conducting multiple trials, which include increasing sample size to increase statistical power; identifying the most effective program design; increasing external validity; and learning how various factors affect program impact. The paper discusses reasons why program design varies across sites, including adaptations to local environment and participant characteristics and a lack of fidelity to the program design. The paper discusses why programs vary across sites and when it is desirable to maintain consistency. Distinctions are drawn between evaluations of pilots and demonstrations versus ongoing programs, as well as programs where variation is permitted or encouraged versus when a fixed design is desired. The paper includes illustrations drawn from evaluations of demonstrations and ongoing programs.

中文翻译：

---

使用多项试验进行评估

本文回顾了多项试验的使用，定义为在一次评估和复制中的多个地点或多个组，以评估社会项目。定义关键术语后，本文讨论了进行多项试验的基本原理，包括增加样本量以增加统计功效；确定最有效的程序设计；增加外部有效性；并了解各种因素如何影响计划的影响。本文讨论了项目设计因站点而异的原因，包括对当地环境和参与者特征的适应以及对项目设计的不忠实。本文讨论了为什么程序会因站点而异，以及何时需要保持一致性。对试点和示范的评估与正在进行的计划之间存在区别，以及允许或鼓励变化而不是需要固定设计的程序。该论文包括从对示范和正在进行的项目的评估中提取的插图。