# PHP | stats_standard_deviation() Function

April 07, 2021

Hello folks! welcome back to a new edition of our tutorial on PHP. In this tutorial guide, we are going to be studying about the PHP

The built-in PHP

*stats_standard_deviation()*function.The built-in PHP

**stats_standard_deviation()**function returns the standard deviation.## Syntax

Following below is the syntax to use this function -

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

## Parameter Details

Sr.No | Parameter | Description |
---|---|---|

1 | a | The array of data to find the standard deviation for. Note that all values of the array will be cast to float. |

2 | sample | Indicates if |

## Return Value

This function returns the standard deviation of the values in

*a*on success, else it returns*false*on failure.## Errors/Exceptions

This built-in function raises an

**E_WARNING**when there are fewer than 2 values in*a*.## Dependencies

This built-in function was first introduced in statistics extension (PHP version 4.0.0 and PEAR v1.4.0). In this tutorial guide, we used the latest release of stats-2.0.3 (PHP v7.0.0 or newer and PEAR version 1.4.0 or newer).

### Example1

The below example computes the standard deviation of the values in an array -

<?php $a=array(4, 1, 7); $dev=stats_standard_deviation($a); var_dump(sprintf("%2.9f", $dev)); ?>

#### Output

When the above code is executed, it will produce the following result -

string(11) "2.449489743"

### Example2

The following example below computes the standard deviation of the values in an array by passing $sample=1 -

<?php $a=array(5,7,8,10,10); var_dump(stats_standard_deviation($a,1)); ?>

#### Output

When the above code is executed, it will produce the following result -

float(2.1213203435596)

### Example3

Following is an error case. In the following example below, we have passed an

*empty array*. A warning is shown in logs -<?php // error cases var_dump(stats_standard_deviation(array())); ?>

#### Output

The above code will produce the following result and a warning in logs

*PHP Warning: stats_standard_deviation(): The array has zero elements*bool(false)

Alright guys! This is where we are going to be rounding up for this tutorial post. In our next tutorial, we are going to be discussing about the built-in

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*stats_stat_binomial_coef()*Function.Feel free to ask your questions where necessary and we will attend to them as soon as possible. If this tutorial was helpful to you, you can use the share button to share this tutorial.

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