Coefficient of Variation

Specifying the standard deviation is more or less useless without the additional specification of the mean (and of course the type of distribution). It makes a big difference if s = 5 with a mean of  = 100, with a mean of  = 3. Relating the standard deviation to the mean resolves this problem. The coefficient of variation is therefore defined by

which is a relative measure of the variation. However you should be aware of the fact that the coefficient of variation becomes more or less useless when the mean approaches zero. So don't use the coefficient of variation for comparing detection limits (where the signal to noise ratio falls below 3).