# stdev

The stdev function calculates the standard deviation of the set of numbers in the specified measure, grouped by the chosen dimension or dimensions, based on a sample.

## Syntax

`stdev(measure, [group-by level])`

## Arguments

measure

The argument must be a measure. Null values are omitted from the results. Literal values don't work. The argument must be a field.

group-by level

(Optional) Specifies the level to group the aggregation by. The level added can be any dimension or dimensions independent of the dimensions added to the visual.

The argument must be a dimension field. The group-by level must be enclosed in square brackets [ ]. For more information, see LAC-A functions.

## Examples

The following example returns the standard deviation of test scores for a class, using a sample of the test scores recorded.

`stdev({Score})`

You can also specify at what level to group the computation using one or more dimensions in the view or in your dataset. This is called a LAC-A function. For more information about LAC-A functions, see LAC-A functions. The following example calculates the standard deviation of test scores at the subject level, but not across other dimensions (Class) in the visual.

`stdev({Score}, [Subject])`