You are here: irt.org | FOLDOC | 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 (http://dictionary.com/)].

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

(2003-05-06)

Nearby terms: standard « Standard Commands for Programmable Instruments « Standard d'Echange et de Transfert « **standard deviation** » standard for robot exclusion » Standard for the exchange of product model data » Standard Generalised Markup Language

FOLDOC, Topics, A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, ?, ALL