Is your feature request related to a problem or challenge?

The excess kurtosis (Fisher's definition) with bias correction according to the sample size.

Describe the solution you'd like

D SELECT kurtosis(col) FROM VALUES (1), (10), (100), (10), (1) as tab(col);
┌───────────────────┐
│   kurtosis(col)   │
│      double       │
├───────────────────┤
│ 4.777292927667962 │
└───────────────────┘

Describe alternatives you've considered

No response

Additional context

https://clickhouse.com/docs/en/sql-reference/aggregate-functions/reference/kurtsamp
https://duckdb.org/docs/sql/functions/aggregates#kurtosisx