Statistical aggregate functions calculate measures of spread, distribution, and central tendency beyond simple averages, enabling sophisticated data analysis.

**Core Statistical Functions:**

**Variance & Standard Deviation:**

- VARIANCE(column) - Measures data spread

- STDDEV(column) - Square root of variance

- Higher values = more spread out data

**Percentiles:**

- PERCENTILE_CONT(0.5) - Continuous percentile (interpolated)

- PERCENTILE_DISC(0.5) - Discrete percentile (actual value)

- MEDIAN - 50th percentile

**Use Cases:**

- Salary variance: Identify pay equity issues

- Performance percentiles: Benchmark employees

- Quality control: Detect outliers

- A/B testing: Statistical significance

**Pattern:**

SELECT

department,

AVG(salary) AS avg_salary,

STDDEV(salary) AS salary_spread,

PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY salary) AS median_salary

FROM employees

GROUP BY department;

Essential for data scientists, analysts, and BI developers doing advanced analytics, A/B testing, quality control, and statistical reporting.

Statistical functions power advanced analytics: salary variance for pay equity, percentiles for performance benchmarking, standard deviation for quality control, median for outlier-resistant averages.