Variance
DEFINATION
方差是在概率论和统计方差衡量随机变量或一组数据时离散程度的度量。
Represent
often represented by \[\sigma ^{2}\] ,\[s^{2}\], \[\operatorname {Var} (X)\], V(X), or\[{\displaystyle \mathbb {V} (X)} \]
Formula
\begin{equation} \[S^2 = \frac{\sum (x_i - \bar{x})^2}{n - 1}\] \[S^2 = {sample\ variance}\] \[x_i = {the\ value\ of\ the\ one\ observation}\] \[\bar{x} = the\ mean\ value\ of\ all\ observations\] \[n = the number of observations\] \end{equation}