# stats_standard_deviation

(PECL stats >= 1.0.0)

stats_standard_deviation — Returns the standard deviation

### 说明

stats_standard_deviation ( array `$a` [, bool `$sample` = `FALSE` ] ) : float

Returns the standard deviation of the values in `a`.

### 参数

`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`.

### 返回值

Returns the standard deviation on success; `FALSE` on failure.

### 错误／异常

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