The Simpson's paradox unraveled

Miguel A Hernán, David Clayton, Niels Keiding

90 Citations (Scopus)

Abstract

Background: In a famous article, Simpson described a hypothetical data example that led to apparently paradoxical results. Methods: We make the causal structure of Simpson's example explicit. Results: We show how the paradox disappears when the statistical analysis is appropriately guided by subject-matter knowledge. We also review previous explanations of Simpson's paradox that attributed it to two distinct phenomena: confounding and non-collapsibility. Conclusion: Analytical errors may occur when the problem is stripped of its causal context and analyzed merely in statistical terms. Published by Oxford University Press on behalf of the International Epidemiological Association.

Original languageDanish
JournalInternational Journal of Epidemiology
Volume40
Issue number3
Pages (from-to)780-785
Number of pages6
ISSN0300-5771
DOIs
Publication statusPublished - Jun 2011

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