External Validity

This website provides tools and frameworks to implement and evaluate external validity in social inquiry, including its two key variants: generalizability and transportability. Explore our conceptual foundations, interactive web tools, and R package for conducting rigorous external validity inference. Our forthcoming book, External Validity Inference for Social Inquiry (Cambridge University Press, Under Contract), offers a comprehensive treatment of these ideas.

Closing the Gap

External validity captures the extent to which inferences apply to a broader population or a new population. While the credibility revolution has produced tens of thousands of causally well-identified studies, it is often unclear how these results apply beyond their immediate objects of investigation. External validity is both everywhere and nowhere: everywhere because the overwhelming majority of studies seek to generalize their findings, and nowhere because so few studies credibly draw broad conclusions. The practical task facing researchers is to make accurate inferences regardless of how broadly those inferences apply.

Making credible external validity inferences is increasingly possible. Advances in causal theory now formalize how effects travel across contexts, design strategies embed generalizability from the start, and modern analytical tools bridge the gap from sample to population with rigor.

This site provides tools and frameworks to help researchers move closer to that goal—where inferred and actual external validity align. Drawing on our forthcoming book and accompanying R package, we offer conceptual foundations, practical guidance, and interactive tools for implementing external validity inference in your own research.

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