Understanding Simpson's Paradox

9 Pages Posted: 26 Oct 2013

See all articles by Judea Pearl

Judea Pearl

University of California, Los Angeles (UCLA) - Computer Science Department

Date Written: September 19, 2013


Simpson's paradox is often presented as a compelling demonstration of why we need statistics education in our schools. It is a reminder of how easy it is to fall into a web of paradoxical conclusions when relying solely on intuition, unaided by rigorous statistical methods. In recent years, ironically, the paradox assumed an added dimension when educators began using it to demonstrate the limits of statistical methods, and why causal, rather than statistical considerations are necessary to avoid those paradoxical conclusions (Arah, 2008; Pearl, 2009, pp. 173-182; Wasserman, 2004).

My comments are divided into two parts. First, I will give a brief summary of the history of Simpson's paradox and how it has been treated in the statistical literature in the past century. Next I will ask what is required to declare the paradox "resolved," and argue that modern understanding of causal inference has met those requirements.

Suggested Citation

Pearl, Judea, Understanding Simpson's Paradox (September 19, 2013). Available at SSRN: https://ssrn.com/abstract=2343788 or http://dx.doi.org/10.2139/ssrn.2343788

Judea Pearl (Contact Author)

University of California, Los Angeles (UCLA) - Computer Science Department ( email )

4732 Boelter Hall
Los Angeles, CA 90095
United States

HOME PAGE: http://www.cs.ucla.edu/~judea/

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