Jolyn

2.58 is the exact number and usually one would say "more than 99% of observations are within 3 sigma of the mean"

Edit: Distributions which have tails as thin as normal are rare as rubies in the real world so 3 sigma is a pretty good real-world number.



Edited 1 time(s). Last edit at Sunday, May 15, 2011 at 12:01PM by JoeyDVivre.