Damo.. you do crack me up sometimes.....
Standard Deviation
From Wikipedia, the free encyclopedia.
In probability and statistics, the standard deviation is the most commonly used measure of statistical dispersion. Simply put, it measures how spread out the values in a data set are.
The importance of the standard deviation arises from Chebyshev's theorem, which asserts that in any data set, nearly all of the values will be close to the mean value, where the meaning of "close to" is specified by the standard deviation.