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

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

Mean square deviation

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

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

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

Mean of all squared data

Mean of all data then squared

All data

No, it ignores outliers

$\sigma$ (standard deviation)