Theory. "We think that X comes from Y and the reasoning is ..." and then somebody else says the exact opposite, with an equally likely-sounding reasoning, and then you don't know what to do. "Evidence-based" means "shown to work - we may not know why, but at least it does".
On this topic, I recently realized the dangers in trying to propagate "evidence-based" throughout all sectors of healthcare. A nurse was complaining about a doctor questioning if a certain drug was safe for breast-feeding women (well for the child, actually). Indignantly, the nurse said "but this manual right here says it's safe! How much more evidence-based can it get!". To her, "the book says so" was "evidence". 'Evidence-based medicine' is no panacea - the principles maybe, but the hard part is in the implementation.
What's the alternative? Nurses don't trust manuals? Obviously as a society we should always strive for better science. But just like lady justice wears a blindfold, nurses should follow the manual.
Of course, that wasn't my point; my point is that when 'evidence based' becomes a mantra that is malunderstood by many, its use in inappropriate contexts devaluates the word and with that, the concept itself.
"Evidence-based" means that you tie statistical outcomes to procedures as apposed to doing what you think might be right based on your limited life experience (which is biased).
For example, let's say there is a test that checks for a birth defect that must be treated or it will result in infant mortality. Let's also say that the test causes infant mortality one time in 10,000. Whether you perform the test has to do with the statistical likelihood that the fetus will have the birth defect - if the likelihood is less than the probability of the test killing the baby then you shouldn't do it.
