Given the widespread use of nonexperimental (NE) methods for assessing program impacts, there is a strong need to know whether NE approaches yield causally valid results in field settings. In within-study comparison (WSC) designs, the researcher compares treatment effects from an NE with those obtained from a randomized experiment that shares the same target population. The goal is to assess whether the stringent assumptions required for NE methods are likely to be met in practice. This essay provides an overview of recent efforts to empirically evaluate NE method performance in field settings. We discuss a brief history of the design, highlighting methodological innovations along the way. We also describe papers that are included in this two-volume special issue on WSC approaches and suggest future areas for consideration in the design, implementation, and analysis of WSCs.

中文翻译：

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从非实验方法的经验评估中可以学到什么？

鉴于非实验（NE）方法广泛用于评估计划的影响，迫切需要了解NE方法是否在现场设置中产生因果有效的结果。在研究内部比较（WSC）设计中，研究人员将NE的治疗效果与共享相同目标人群的随机实验获得的效果进行了比较。目的是评估在实践中是否有可能满足NE方法所需的严格假设。本文概述了最近在现场设置中根据经验评估NE方法性能的工作。我们讨论设计的简要历史，重点介绍沿途的方法创新。我们还将介绍此两卷有关WSC方法的专刊中包含的论文，并建议在设计中应考虑的未来领域，