Evaluating Evidence Quality
The gold standard of all scientific studies in EMS and
medicine are large, multi-centre, double-blind,
randomized controlled trials performed on human
• Three tourists are riding together on a train in
Scotland. They look out the window, and see a
black sheep. One tourist says, “Fascinating! All
Scottish sheep are black!”
• The second tourist says, “No, no, no! Only some
Scottish sheep are black.”
• The third tourist rolls his eyes at his two
companions and says, “Gentlemen, all we can say
for sure is that there is one sheep in Scotland that
appeared to be black on one side to the three of us
while this train car was passing by it.”
• Sackett DL, Rosenberg WM, Gray JA, Haynes RB,
Richardson WS. Evidence based medicine: what it is
and what it isn’t. BMJ. 1996 Jan 13;312(7023):71-2.
• Hess DR. What is evidence-based medicine and why
should I care? Respir Care. 2004 Jul;49(7):730-41.
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