مقایسهٔ روش‌ها

	آزمایش طبیعی	روش تفاوت در تفاوت (Diff-in-Diff)
حوزه	طراحی آزمایش	اقتصادسنجی
خانواده	Process / pipeline	Regression model
سال پیدایش	1990s (formal methodological articulation); earlier in epidemiology (John Snow, 1854)	1994
پدیدآور	Varied; systematized in econometrics and political science (e.g., Meyer 1995; Angrist & Krueger 1991)	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)
نوع	Quasi-experimental research design	Causal inference / panel regression
منبع بنیادین	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
نام‌های دیگر	natural quasi-experiment, naturally occurring experiment, exogenous shock design, as-if randomization	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)
مرتبط	3	5
خلاصه	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.