What is it about?
Argues that the indefinite unmeasured confounders argument of Worrall is not a valid criticism of probabilistic arguments for randomisation. Furthermore, even if this criticism were valid it would not be sufficient to give observational studies the same status as interventional ones.
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Why is it important?
Shows that "RCTs offer unique epistemological advantages that cannot be realised via observational studies."
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This page is a summary of: What does randomisation achieve?, Evidence-Based Medicine, June 2011, BMJ,
DOI: 10.1136/ebm.2011.100061.
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Indefinite irrelevance
The argument that indefinitely many confounders invalidates randomisation is wrong for the same reason that it is wrong to claim that the series 1/2 + 1/4 +1/8..... does not converge because there are infinitely many terms.
Lecture on Randomisation, Bristol September 2011
Discusses seven myths of randomisation
Seven myths of randomisation in clinical trials
The result of an analysis of a randomised clinical trial (RCT) is a probability statement. To query the validity of the analysis it is necessary to show that the probability statement makes an invalid statement in probability. When this is properly understood then many commonly held beliefs about RCTs can be shown to be incorrect.
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