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How to Learn about Causes in the Single Case

Cartwright, Nancy

How to Learn about Causes in the Single Case Thumbnail



Jennifer Widner

Michael Woolcock

Daniel Ortega Nieto


RCTs have gained considerable prominence as a ‘gold standard’ for establishing whether a given policy intervention has a causal effect, but what do these experiments actually tell us and how useful is this information for policy-makers? Cartwright draws attention to two problems. First, an RCT only establishes a claim about average effects for the population enrolled in an experiment; it tells us little about what lies behind the average. The policy intervention studied might have changed nothing in some instances, while in others it triggered large shifts in behavior or health or whatever is under study. But, second, an RCT also tells us nothing about when we might expect to see the same effect size in a different population. In short, “identifying a cause is not the same as identifying something that is generally true,” Cartwright says. To assess how a different population might respond requires other information of the sort that qualitative case studies often uncover. Cartwright identifies the key elements we need to know in order to decide whether the effects observed in an experiment will scale.


Cartwright, N. (2022). How to Learn about Causes in the Single Case. In J. Widner, M. Woolcock, & D. Ortega Nieto (Eds.), . Cambridge University Press.

Publication Date May 26, 2022
Deposit Date Jun 21, 2024
Publicly Available Date Jun 21, 2024
Pages 29-51
ISBN 9781108427272
Public URL


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