方法对比

	自然实验	双重差分法 (Diff-in-Diff)	随机对照试验 (RCT)
领域	实验设计	计量经济学	实验设计
方法族	Process / pipeline	Regression model	Hypothesis test
起源年份	1990s (formal methodological articulation); earlier in epidemiology (John Snow, 1854)	1994	1948
提出者	Varied; systematized in econometrics and political science (e.g., Meyer 1995; Angrist & Krueger 1991)	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)	James Lind (early precursor, 1747); modern formulation: Austin Bradford Hill & Medical Research Council (1948)
类型	Quasi-experimental research design	Causal inference / panel regression	Interventional comparative study
开创性文献	Meyer, B. D. (1995). Natural and quasi-experiments in economics. Journal of Business and Economic Statistics, 13(2), 151–161.	Angrist, J. D., & Pischke, J.-S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton University Press. ISBN: 978-0691120355	Schulz, K.F., Altman, D.G., Moher, D., for the CONSORT Group (2010). CONSORT 2010 Statement: Updated Guidelines for Reporting Parallel Group Randomised Trials. BMJ, 340, c332.
别名	natural quasi-experiment, naturally occurring experiment, exogenous shock design, as-if randomization	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)	RCT, randomised controlled trial, clinical trial, Randomize Kontrollü Çalışma (RCT) Tasarımı
相关	3	5	7
摘要	A natural experiment exploits a real-world event, policy, or circumstance that assigns individuals to treatment and control conditions in a way that is plausibly random — or at least exogenous to the outcome of interest. Because the researcher does not control assignment, it occupies a middle ground between a true randomized controlled trial and purely observational research, offering stronger causal leverage than conventional observational designs when the as-if randomization assumption holds.	Difference-in-Differences is a causal-inference method that estimates the effect of an intervention by comparing how a treatment group and a control group change over time. Made famous by Card and Krueger's 1994 minimum-wage study and developed in Angrist and Pischke's Mostly Harmless Econometrics, it isolates the treatment effect as the difference between the two groups' before-after changes.	A randomized controlled trial (RCT) is the gold standard experimental design in clinical and health research, in which participants are randomly allocated to a treatment group or a control group so that the effect of an intervention can be measured with the highest possible degree of internal validity. The modern parallel-group RCT was formalized by Austin Bradford Hill and the Medical Research Council in their landmark streptomycin trial of 1948, and its reporting is governed today by the CONSORT 2010 guidelines (Schulz et al., 2010).