stats_standard_deviation

(PECL stats >= 1.0.0)

stats_standard_deviation — Returns the standard deviation

float stats_standard_deviation ( array $a [, bool $sample = false ] )

a: The array of data to find the standard deviation for. Note that all values of the array will be cast to float.
sample: Indicates if a represents a sample of the population; defaults to FALSE.

Returns the standard deviation on success; FALSE on failure.

Raises an E_WARNING when there are fewer than 2 values in a.