Berwick DM. The science of improvement. Journal of the American Medical Association. 2008 Mar;299(10):1182-1184.
Individuals most involved in day-to-day improvement work in health care fear that if "evidence" is too narrowly defined and the approach to gathering evidence too severely constrained, progress may be the victim. The author discusses the question, "How can accumulating local reports of effectiveness of improvement interventions... be reconciled with contrary findings from formal trials with their own varying imperfections?"