Answers are grounded in this paper and cite their sources.
Citation: Rothwell, P. M. (2006). 'Factors that can affect the external validity of randomised controlled trials' PLoS Clinical Trials, 1(1): e9. [Available at http://clinicaltrials.ploshubs.org]. Copyright 2006 Peter M. Rothwell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
No takes yet. Share an insight, caveat, or question.
Peter M. Rothwell (2006) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: