juniorStatistics
What is variance and standard deviation?
Updated May 17, 2026
Short answer
Variance measures spread; standard deviation is its square root.
Deep explanation
Variance measures average squared deviation from mean, while standard deviation expresses dispersion in original units.
Real-world example
Stock price volatility is measured using standard deviation.
Common mistakes
- Confusing variance units with original data units.
Follow-up questions
- Why square deviations?
- What does high variance indicate?