**Performance Tips:**

- Statistical functions require full group scan

- More computationally expensive than simple aggregates

- Index columns used in ORDER BY for percentiles

- Consider materialized views for frequent calculations

Statistical functions computationally expensive

Require full group scan

Index ORDER BY columns for percentiles

Consider materialized views for frequent use

Test performance with production data volumes

Misinterpreting standard deviation magnitude

Using AVG when MEDIAN more appropriate

Ignoring sample size for statistical validity

Not handling NULL values appropriately

Forgetting database-specific syntax