RCTs: Where’s the rigor when you need it?
Randomised controlled trails are taken as gold standard evidence for policy effectiveness almost everywhere evidence-based policy is preached. Development economics is no exception – just look at what all those MIT economists say on the J-PAL website. RCTs are supposed to be a paradigm of rigor. That’s true in a sense. It is provable that if the treatment is orthogonal to other causes, the mean of the outcome in the treatment group minus the mean in the control group is an unbiased estimate of the average treatment effect (ATE) in the study population. But this theorem is of little use. Why suppose the premise is ever satisfied? Randomisation may give orthogonality at base but much happens differentially to the two groups after. And of what use as evidence about my setting is an ATE in a total different setting? Both warranting orthogonality and warranting transport of the ATE elsewhere (with or without adjustment) requires just the kind of knowledge of the ‘unknown unknowns’ that RCTs are meant to avoid need for. When it comes to putting RCT results to use, rigor gives out very quickly.
Nancy Cartwright is Professor of Philosophy at the Department of Philosophy, University of Durham and at the University of California, San Diego (UCSD). She is past President of the Philosophy of Science Association and was President of the American Philosophical Association (Pacific Division) in 2008. Her research interests include philosophy and history of science (especially physics and economics), causal inference, causal powers, scientific emergence and objectivity, evidence, especially for evidence-based policy [EBP] and the philosophy of social technology. Her current work, for the project ‘Knowledge for Use’ [K4U], investigates how to use scientific research results for better policies.
Nancy Cartwright is a Fellow of the British Academy and a member of the American Philosophical Society (The US’s oldest academic honourary society), the American Academy of Arts and Sciences, the German Academy of Sciences (Leopoldina) and a recipient of a MacArthur Fellowship. She has published numerous books, book chapters and articles in leading international journals.
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|18 Apr 2018||4:30pm - 6:00pm|
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