# STDDEVP

Returns the population standard deviation of a given expression, across all elements of a set.

## Returned Type

This function returns a number.

## Syntax and Details

```STDDEVP(set_expression, optional_numeric_expression)
```
Where:
• set_expression is an expression that evaluates to a set, typically a set of members or tuples.
• optional_numeric_expression is a numeric-valued expression that the function evaluates for each set element.
Typically, this expression has the form
[MEASURES].[
measure_name
]
If you do not specify a numeric expression, DeepSee uses the measure used by the current result cell.
The function evaluates the numeric value for each element of the set and returns the population standard deviation of those values.

## Example

First, the following query shows two measure values for the members of the
level:
```SELECT {MEASURES.[%COUNT],MEASURES.[encounter count]} ON 0,
Patient Count      Encounter Count
1 1910s                           80                5,359
2 1920s                          227               12,910
3 1930s                          567               33,211
4 1940s                          724               38,420
5 1950s                        1,079               46,883
6 1960s                        1,475               57,814
7 1970s                        1,549               49,794
8 1980s                        1,333               35,919
9 1990s                        1,426               29,219
10 2000s                        1,406               20,072
11 2010s                          134                1,346
```
Next, the following query shows the population standard deviations for these measures for the members of this level:
```SELECT {MEASURES.[%COUNT],MEASURES.[encounter count]} ON 0,
Patient Count      Encounter Count
STDDEVP                        552.44            17,544.98
```
Here, each value is the population standard deviation of the values in a column in the preceding query. For example, the
Patient Count
value is the population standard deviation of the
Patient Count
values in the preceding query.
For another example, we use the second argument for STDDEVP:
```SELECT STDDEVP(birthd.decade.MEMBERS, MEASURES.[%COUNT]) ON 0 FROM patients
STDDEVP
552.44
```
For additional, similar examples, see AVG.