php man page for stats_standard_deviation

STATS_STANDARD_DEVIATION(3)						 1					       STATS_STANDARD_DEVIATION(3)

stats_standard_deviation - Returns the standard deviation

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

DESCRIPTION
PARAMETERS
	      o $a
		- The array of data to find the standard deviation for. Note that all values of the array will be cast to float.

	      o $sample
		- Indicates if $a represents a sample of the population; defaults to FALSE.

RETURN VALUES
	Returns the standard deviation on success; FALSE on failure.

ERRORS
/EXCEPTIONS
	Raises an E_WARNING when there are fewer than 2 values in $a.

PHP Documentation Group 											       STATS_STANDARD_DEVIATION(3)