 |
 |
However, I don't think that it is necessary for RCTs to control for all confounders for valid inference to be based on them and it is precisley this point that I think many commentators are confused on. Stephen Stephen Senn Professor of Statistics School of Mathematics and Statistics Direct line: +44 (0)141 330 5141 Fax: +44 (0)141 330 4814 Private Webpage: http://www.senns.demon.co.uk/home.html University of Glasgow 15 University Gardens Glasgow G12 8QW The University of Glasgow, charity number SC004401 ________________________________________ From: Evidence based health (EBH) [[log in to unmask]] On Behalf Of Jeremy Howick [[log in to unmask]] Sent: 30 January 2011 23:20 To: [log in to unmask] Subject: Can RCT help establish causation? A philosopher's reply Dear All, Stephen is correct that philosophers have been discussing the issue of how to establish scientific knowledge for centuries – if not longer – and it is fair to say that there is no widely accepted response to the problem Hume posed. (Hume famously argued that while we would be 'fools or madmen' to NOT accept scientific knowledge, inductive reasoning upon which scientific laws are base have no rational justification (for a simple explanation see: en.wikipedia.org/wiki/Problem_of_induction).) However, philosophers (and others) HAVE managed to provide "a scientific method that allows us to LOGICALLY distinguish coincidence from causation". See, for example, Cartwright (2007): journals.cambridge.org/action/displayAbstract?fromPage=online&aid=1002668 A simple way to put Cartwright's claim is: "if RCTs control for all confounders, then their conclusions about the causal properties of the intervention are valid". The problem, of course, is that even the best randomized trial DO NOT control for ALL confounders. They are better than other methods at ruling out confounders, but are not perfect. Hence the EBM insistence that we keep UP TO DATE with the latest evidence that might overturn previous evidence. I try to explain this clearly in my forthcoming book (http://www.amazon.co.uk/Philosophy-Evidence-Based-Medicine-Jeremy-Howick/dp/140519667X). Best wishes, Jeremy From: "[log in to unmask]<mailto:[log in to unmask]>" <[log in to unmask]<mailto:[log in to unmask]>> Reply-To: "[log in to unmask]<mailto:[log in to unmask]>" <[log in to unmask]<mailto:[log in to unmask]>> Date: Fri, 28 Jan 2011 15:06:33 +0000 To: "[log in to unmask]<mailto:[log in to unmask]>" <[log in to unmask]<mailto:[log in to unmask]>> Subject: Can RCT help establish causation? Dear all I'd like to post this question to the group that I have been thinking about for some time... Is there a scientific method that allows us to LOGICALLY distinguish the cause-effect from the coincidence? David Hume, one of the most influential philosophers of all times, concluded that there is no such a method. This was before RCTs were "invented". Many people have made cogent arguments that (a well done) RCT is the ONLY method that can allow us to draw the inferences about causation. Because this is not possible in the observational studies, RCTs are considered (all other things being equal) to provide more credible evidence than non-RCTs. However, some philosophers have challenged this supposedly unique feature of RCT- they claim that RCTs cannot (on theoretical and logical ground) establish the relationship between the cause and effect any better than non-RCTs. I would appreciate some thoughts from the group: 1. Can RCT distinguish between the cause and effect vs. coincidences? (under which -theoretical- conditions?) If the answer is "no", is there any other method that can help establish the cause and effect relationship? I believe the answer to this question is of profound relevance to EBM. Thanks Ben Djulbegovic