standard deviation

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The standard deviation (σ) is a measure of spread in \term{statistics}. It is caclualted by taking the square root of the \term{variance}, which is itself the average of the square of difference of values from their \term{arithmetic mean}. The standard deviation of a simple set of N numbers x_i> with mean μ is:
      σ   =   √ ( Σ (x_i>− μ)²  /  N )

Defined on page 139

Used on Chap. 7: pages 138, 139, 140; Chap. 8: page 162; Chap. 10: pages 207, 209; Chap. 12: page 258