Calculate standard deviation, variance, mean, median, mode, and range for any dataset. Supports both population (σ) and sample (s) formulas.
Measures how spread out data is from the mean. Low SD = clustered near average. High SD = widely spread.
Population SD divides by N (all data). Sample SD divides by N-1 (a sample of a larger group).
Find the mean, subtract mean from each value and square, average those squares (variance), take the square root.
In a normal distribution: 68% of data falls within 1 SD, 95% within 2 SD, 99.7% within 3 SD of the mean.
All values are identical. No spread exists.