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Are RCTs the gold standard?

Cartwright, N. (2007) 'Are RCTs the gold standard?', BioSocieties., 2 (1). pp. 11-20.


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.

Item Type:Article
Additional Information:Also as "Technical Report 01/07" (2007), Contingency and Dissent in Science Series, CPNSS, LSE. Also in N. Cartwright (2007), Causal Powers.
Keywords:Causal inference, External validity, Hypothetico-deductive method, Internal validity, Randomized controlled trials.
Full text:(AM) Accepted Manuscript
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Publisher statement:This is a post-peer-review pre-copyedit version of an article published in BioSocieties. The definitive publisher-authenticated version Cartwright, N. (2007) 'Are RCTs the gold standard?', BioSocieties., 2 (1): 11-20 is available online at:
Date accepted:No date available
Date deposited:12 February 2016
Date of first online publication:March 2007
Date first made open access:No date available

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