Variance, $\sigma^2 = \overline{x^2} - (\overline{x})^2$
A mnemonic...
Mean of squares minus square of mean.
and then remember that standard deviation, $\sigma$, is the sqrt of variance.
Variance, $\sigma^2 = \overline{x^2} - (\overline{x})^2$
A mnemonic...
Mean of squares minus square of mean.
and then remember that standard deviation, $\sigma$, is the sqrt of variance.