Statistics & Probability
Intermediate

Standard Deviation

Square root of the variance; typical spread.

Formula

σ=1n∑i=1n(xi−xˉ)2\sigma = \sqrt{\frac{1}{n}\sum_{i=1}^{n}(x_i-\bar{x})^2}

Variables

x_iData values
\bar{x}Mean
nCount

Example

For 2, 4, 6: σ = √2.67 ≈ 1.63.

Did You Know?

Standard deviation is the "typical" distance from the mean — and its units match the data, unlike variance.

standard deviationspread