Variance Calculator
Variance measures how spread out a dataset is from its mean. Enter your numbers to get variance, standard deviation, and a full statistical summary.
How It Works
Computes the mean, then finds squared deviations. Uses n−1 for sample variance (Bessel's correction) or n for population variance.
Formula
Population: σ² = Σ(x⊂i−μ)²/N
Sample: s² = Σ(x⊂i−x̄)²/(N−1)
SD = √Variance
Example
Dataset: 2, 4, 6, 8. Mean=5. Squared deviations: 9+1+1+9=20.
Pop variance=5. SD=2.236
When to Use This Calculator
Use in statistics homework, data analysis, quality control, or any situation requiring measurement of data spread.
Common Mistakes to Avoid
- Wrong type — sample (n−1) for subsets; population (n) for all data.
- Not squaring deviations — variance uses squared differences to eliminate negatives.
- Confusing variance with SD — SD is in original units; variance is squared units.
Frequently Asked Questions
High variance means?
Data points are widely spread from the mean.
Is SD more useful?
SD is more interpretable (same units as data). Variance is used in many statistical formulas.
Sample vs population?
Sample (n−1) when your data represents a larger population. Population (n) when you have all data.
Coefficient of variation?
CV = (SD/Mean) × 100. Compares variability across datasets with different scales.
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Last Updated: July 4, 2026