Random Sample's Sample Mean Average and Variance
Formulas
Given a random sample $X_{1} , \cdots , X_{n} \overset{\text{iid}}{\sim} X$, the mean and variance of its sample mean $\bar{X}$ are as follows. $$ \begin{align*} E \bar{X} =& E X \\ \operatorname{Var} \bar{X} =& {{ 1 } \over { n }} \operatorname{Var} X \end{align*} $$