# StdDev

## Description

Calculates the standard deviation of an aggregation of values.

## Syntax

StdDev ( n )

## Arguments

`n` is a numeric expression.

## Example

Returns the average and standard deviation of each continent's female population.

```
select Continent, Avg(Pop_Fem) as Average, StdDev(Pop_Fem) as StandardDeviation from countries group by Continent
```

## Remarks

StdDev is an aggregation function which can only be used in an aggregating `Select` statement. Null values are ignored. If there are only null values supplied in the aggregation, then a null value is returned.