# `STDDEV_POP`

**Applies to:** ✅ Data 360 SQL ✅ Tableau Hyper API

Computes the population standard deviation of input values.

## Syntax

```sql
stddev_pop(<expression>)
```

## Arguments

### Required

- `<expression>`: An expression of any numerical type.

## Returns

- `NUMERIC(38,6)` for integer-type or numeric arguments.
- `double precision` for floating-point arguments.

Returns NULL if the computation is meaningless.

## Considerations

- Uses N in the denominator (no Bessel's correction).
- Use `STDDEV_SAMP` or `STDDEV` for sample standard deviation.
- Cast the input to `double precision` to get a `double precision` result.

## Examples

### Calculate Population Standard Deviation

Find the population standard deviation of scores.

```sql
SELECT stddev_pop(score) AS score_stddev
FROM test_results;
```

### Population Standard Deviation by Group

Calculate for each group.

```sql
SELECT region, stddev_pop(sales) AS sales_stddev
FROM regional_sales
GROUP BY region;
```

## Related Documentation

- [STDDEV](/docs/data/data-cloud-query-guide/references/dc-sql-reference/stddev.md)
- [STDDEV](/docs/data/data-cloud-query-guide/references/dc-sql-reference/stddev.md)
- [VAR_POP](/docs/data/data-cloud-query-guide/references/dc-sql-reference/var-pop.md)
- [Aggregate Functions](/docs/data/data-cloud-query-guide/references/dc-sql-reference/aggregate.md)