# Standard Deviation

**Standard Deviation** is the square root of the variance.

It has the same units as the data.

$$SD = \sqrt{\frac{\sum_{i=1}^{n}(x_i-\bar{x})^2}{n-1}}$$

**Standard Deviation** is the square root of the variance.

It has the same units as the data.

$$SD = \sqrt{\frac{\sum_{i=1}^{n}(x_i-\bar{x})^2}{n-1}}$$