Add stddevPopStable

docs/en/sql-reference/aggregate-functions/reference/stddevpop.md

@@ -12,7 +12,7 @@ Alias:
 - `STDDEV_POP`
 
 :::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` function. It works slower but provides a lower computational error.
+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/stddevpopstable.md) function. It works slower but provides a lower computational error.
 :::
 
 **Syntax**

docs/en/sql-reference/aggregate-functions/reference/stddevpopstable.md

@@ -0,0 +1,53 @@
+---
+slug: /en/sql-reference/aggregate-functions/reference/stddevpopstable
+sidebar_position: 30
+---
+
+# stddevPopStable
+
+The result is equal to the square root of [varPop](../../../sql-reference/aggregate-functions/reference/varpop.md). Unlike [`stddevPop`](../reference/stddevpop.md), this function uses a numerically stable algorithm. It works slower but provides a lower computational error.
+
+:::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` function. It works slower but provides a lower computational error.
+:::
+
+**Syntax**
+
+```sql
+stddevPopStable(x)
+```
+
+**Parameters**
+
+- `x`: Population of values to find the standard deviation of. [(U)Int*](../../data-types/int-uint.md), [Float*](../../data-types/float.md), [Decimal*](../../data-types/decimal.md).
+
+**Returned value**
+
+Standard deviation of `x`. [Float64](../../data-types/float.md).
+
+**Example**
+
+Query:
+
+```sql
+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;
+```
+
+Result:
+
+```response
+┌─────────────stddev─┐
+│ 1.2999977786592576 │
+└────────────────────┘
+```