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	Blockerad naturlig experiment	Differens-i-differens (DiD)
Ämnesområde	Försöksplanering	Ekonometri
Familj	Process / pipeline	Regression model
Ursprungsår	Blocking: 1935; natural experiments as formal causal framework: 1990s–2000s	1994
Upphovsperson	Combines Fisher's blocking principle (1935) with natural experiment methodology formalized by Angrist and Pischke (2009)	Card & Krueger (canonical 1994 application); Angrist & Pischke (textbook treatment)
Typ	Quasi-experimental causal design	Causal inference / panel regression
Ursprungskälla	Angrist, J. D., & Pischke, J.-S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton University Press. ISBN: 978-0691120355	Angrist, J. D., & Pischke, J.-S. (2009). Mostly Harmless Econometrics: An Empiricist's Companion. Princeton University Press. ISBN: 978-0691120355
Alias	stratified natural experiment, block-stratified quasi-experiment, natural experiment with blocking	diff-in-diff, DiD, Farkların Farkı (Diff-in-Diff)
Närliggande	3	5
Sammanfattning	A blocked natural experiment is a quasi-experimental design that exploits naturally occurring, researcher-uncontrolled variation in treatment assignment while pre-stratifying (blocking) units on key observed covariates. Blocking absorbs between-stratum variance, improves statistical precision, and strengthens the plausibility of the as-if-random assumption within each block. The design draws on Fisher's blocking principle and the natural experiment tradition in economics and epidemiology.	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.