standard deviation

statistics (SD) A measure of the range of values in a set of

numbers. Standard deviation is a statistic used as a measure

of the dispersion or variation in a distribution, equal to the

square root of the arithmetic mean of the squares of the

deviations from the arithmetic mean.

The standard deviation of a random variable or list of numbers

(the lowercase greek sigma) is the square of the variance.

The standard deviation of the list x1, x2, x3...xn is given by

the formula:

sigma = sqrt(((x1-(avg(x)))^2 + (x1-(avg(x)))^2 +

... + (xn(avg(x)))^2)/n)

The formula is used when all of the values in the population

are known. If the values x1...xn are a random sample chosen

from the population, then the sample Standard Deviation is

calculated with same formula, except that (n-1) is used as the

denominator.

[dictionary.com ].

["Barrons Dictionary of Mathematical Terms, second edition"].

(2003-05-06)