the ratio of the quadratic deviation to the average value. In variational statistics the difference of any set of positive numbers x1,... ,xn from their arithmetic average x¯ = (x1 +... xn)/n is characterized by the standard deviation
A relative characteristic of such “scatter” is the coefficient of variation s/x¯. In probability theory and mathematical statistics the coefficient of variation of a positive random quantity X is defined as the ratio σ/a, where a = EX is the mathematical expectation, and σ2 = DX = E(X -a)2 is the dispersion. If X is the result of the measurement of some unknown positive constant a = EX, then the coefficient of variation is a natural characteristic of the relative error of measurement.