摘要翻译：
自然实验一词的使用不一致。在一种解释中，它指的是由研究人员以外的人随机分配治疗的实验。在另一种解释中，它指的是一项研究，在这项研究中，没有受控的随机分配，但治疗是由某种外部因素以一种大致类似于随机实验的方式分配的--通常被描述为“似乎随机”的分配。在另一种解释中，它指的是任何将治疗与对照组进行比较的非随机研究，对如何分配治疗没有任何具体要求。我引入了一个替代定义，它试图澄清自然实验的整体特征，同时将它们与随机对照实验区分开来。我将自然实验定义为一种研究性研究，其中治疗分配机制(I)既不是由研究者设计也不是由研究者实施的，(ii)是研究者未知的，(iii)由于依赖于外部因素而具有概率性。这个定义的主要信息是，随机对照实验和自然实验之间的区别不是程度问题，而是本质问题，因此把自然实验概念化为类似随机实验的研究设计既不严格，也不是经验分析的有用指南。使用我的另一个定义，我讨论了自然实验与传统观察研究的区别，并为希望使用自然实验来研究因果效应的研究人员提供了实用的建议。
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英文标题：
《Natural Experiments》
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作者：
Rocio Titiunik
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最新提交年份：
2020
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分类信息：

一级分类：Statistics        统计学
二级分类：Methodology        方法论
分类描述：Design, Surveys, Model Selection, Multiple Testing, Multivariate Methods, Signal and Image Processing, Time Series, Smoothing, Spatial Statistics, Survival Analysis, Nonparametric and Semiparametric Methods
设计，调查，模型选择，多重检验，多元方法，信号和图像处理，时间序列，平滑，空间统计，生存分析，非参数和半参数方法
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一级分类：Economics        经济学
二级分类：Econometrics        计量经济学
分类描述：Econometric Theory, Micro-Econometrics, Macro-Econometrics, Empirical Content of Economic Relations discovered via New Methods, Methodological Aspects of the Application of Statistical Inference to Economic Data.
计量经济学理论，微观计量经济学，宏观计量经济学，通过新方法发现的经济关系的实证内容，统计推论应用于经济数据的方法论方面。
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英文摘要：
  The term natural experiment is used inconsistently. In one interpretation, it refers to an experiment where a treatment is randomly assigned by someone other than the researcher. In another interpretation, it refers to a study in which there is no controlled random assignment, but treatment is assigned by some external factor in a way that loosely resembles a randomized experiment---often described as an "as if random" assignment. In yet another interpretation, it refers to any non-randomized study that compares a treatment to a control group, without any specific requirements on how the treatment is assigned. I introduce an alternative definition that seeks to clarify the integral features of natural experiments and at the same time distinguish them from randomized controlled experiments. I define a natural experiment as a research study where the treatment assignment mechanism (i) is neither designed nor implemented by the researcher, (ii) is unknown to the researcher, and (iii) is probabilistic by virtue of depending on an external factor. The main message of this definition is that the difference between a randomized controlled experiment and a natural experiment is not a matter of degree, but of essence, and thus conceptualizing a natural experiment as a research design akin to a randomized experiment is neither rigorous nor a useful guide to empirical analysis. Using my alternative definition, I discuss how a natural experiment differs from a traditional observational study, and offer practical recommendations for researchers who wish to use natural experiments to study causal effects.
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PDF链接：
https://arxiv.org/pdf/2002.00202