> ## 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. Unlike stddevPop, this function uses a numerically stable algorithm.

# stddevPopStable

<h2 id="stddevPopStable">
  stddevPopStable
</h2>

Introduced in: v1.1.0

The result is equal to the square root of [varPop](/reference/functions/aggregate-functions/varPop). Unlike [stddevPop](/reference/functions/aggregate-functions/stddevPop), this function uses a numerically stable algorithm. It works slower but provides a lower computational error.

**Syntax**

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

**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 the variance of `x`. [`Float64`](/reference/data-types/float)

**Examples**

**Basic usage**

```sql title=Query theme={null}
DROP TABLE IF EXISTS test_data;
CREATE TABLE test_data
(
    population Float64,
)
ENGINE = Log;

INSERT INTO test_data SELECT randUniform(5.5, 10) FROM numbers(1000000);

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

```response title=Response theme={null}
┌─────────────stddev─┐
│ 1.2999977786592576 │
└────────────────────┘
```