Misleading description

No evidence

Look out for a “lack of evidence” being described as evidence of “no difference” in effect.

Systematic reviews sometimes conclude that there is “no evidence of effect” of an intervention. This is often misinterpreted as meaning that there is “no difference” between the action or no action. However, studies can never show that there is “no difference” (“no effect”). They can only rule out, with specific degrees of confidence, differences of a specific size.

REMEMBER: Don’t be misled by statements of “no evidence of impact” (“no effect”). Consider instead the degree to which it is possible to confidently rule out an effect of a specified size.