15 septembre 2022
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info:eu-repo/semantics/altIdentifier/doi/10.2139/ssrn.3520820
http://creativecommons.org/licenses/by-nc/ , info:eu-repo/semantics/OpenAccess
Clément de Chaisemartin et al., « At What Level Should One Cluster Standard Errors in Paired and Small-Strata Experiments? », HAL SHS (Sciences de l’Homme et de la Société), ID : 10.2139/ssrn.3520820
In clustered and paired experiments, to estimate treatment effects, researchers often regress their outcome on the treatment and pair fixed effects, clustering standard errors at the unit-ofrandomization level. We show that even if the treatment has no effect, a 5%-level t-test based on this regression will wrongly conclude that the treatment has an effect up to 16.5% of the time, an error rate much larger than the researcher's 5% target. To achieve their targeted error rate, researchers should instead cluster standard errors at the pair level. Using simulations, we show that similar results apply to clustered experiments with small strata.