Number needed to treat

Source: Your Medical mInd

It is not what it means when the doctor says "By taking a statin pill, you’ll reduce your risk of a heart attack over the next ten years by as much as 30 percent.”. It is not mean that out 100 your risk of h-a reduced by 30%. Doctor here uses 'health literacy' lingo and particularly "Number needed to treat".

http://en.wikipedia.org/wiki/Number_needed_to_treat