The Simpson's paradox unraveled

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