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Are RCTs the Gold Standard?

Published online by Cambridge University Press:  01 March 2007

Nancy Cartwright
Nancy Cartwright
Affiliation:
Department of Philosophy, Logic and Scientific Method, London School of Economics, Houghton Street, London WC2A 2AE, UK E-mail: n.l.cartwright@lse.ac.uk
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Abstract

The claims of randomized controlled trials (RCTs) to be the gold standard rest on the fact that the ideal RCT is a deductive method: if the assumptions of the test are met, a positive result implies the appropriate causal conclusion. This is a feature that RCTs share with a variety of other methods, which thus have equal claim to being a gold standard. This article describes some of these other deductive methods and also some useful non-deductive methods, including the hypothetico-deductive method. It argues that with all deductive methods, the benefit that the conclusions follow deductively in the ideal case comes with a great cost: narrowness of scope. This is an instance of the familiar trade-off between internal and external validity. RCTs have high internal validity but the formal methodology puts severe constraints on the assumptions a target population must meet to justify exporting a conclusion from the test population to the target. The article reviews one such set of assumptions to show the kind of knowledge required. The overall conclusion is that to draw causal inferences about a target population, which method is best depends case-by-case on what background knowledge we have or can come to obtain. There is no gold standard.

Keywords

causal inferenceexternal validityhypothetico-deductive methodinternal validityrandomized controlled trials
Type
Articles
Information
BioSocieties , Volume 2 , Issue 1: Special Issue: The Construction and Governance of Randomised Controlled Trials , March 2007 , pp. 11 - 20
Copyright
Copyright © London School of Economics and Political Science 2007

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