> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-fix-nav-issues.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> The result is equal to the square root of varPop.

# stddevPop

<h2 id="stddevPop">
  stddevPop
</h2>

Introduced in: v1.1.0

Returns the population standard deviation of a numeric data sequence.
The result is equal to the square root of [`varPop`](/reference/functions/aggregate-functions/varPop).

<Note>
  This function uses a numerically unstable algorithm. If you need [numerical stability](https://en.wikipedia.org/wiki/Numerical_stability) in calculations, use the [`stddevPopStable`](/reference/functions/aggregate-functions/stddevPopStable) function. It works slower but provides a lower computational error.
</Note>

**Syntax**

```sql theme={null}
stddevPop(x)
```

**Aliases**: `STD`, `STDDEV_POP`

**Arguments**

* `x` — Population of values to find the standard deviation of. [`(U)Int*`](/reference/data-types/int-uint) or [`Float*`](/reference/data-types/float) or [`Decimal*`](/reference/data-types/decimal)

**Returned value**

Returns the square root of population variance of `x`. [`Float64`](/reference/data-types/float)

**Examples**

**Computing population standard deviation**

```sql title=Query theme={null}
CREATE TABLE test_data (population UInt8) ENGINE = Log;
INSERT INTO test_data VALUES (3),(3),(3),(4),(4),(5),(5),(7),(11),(15);

SELECT stddevPop(population) AS stddev FROM test_data;
```

```response title=Response theme={null}
┌────────────stddev─┐
│ 3.794733192202055 │
└───────────────────┘
```