Standard Deviation & Variance (Edexcel A-Level Mathematics): Flashcards

On average, how far each data point deviates from the mean

Mean square deviation

$\sigma = \sqrt{\sigma^2}$ (SD is square root of variance)

$\sigma^2 = \frac{\Sigma(x-\bar{x})^2}{n}$

$\sigma^2 = \overline{x^2} - (\bar{x})^2$

Mean of all squared data

Mean of all data, then squared

Two data points

Two data points

All data

Includes outliers

Ignores outliers

Includes extreme outliers