Variance

Definition

• Population variance
• Measurement of how spreading a set of values are in a population
• $Var(X)=E[(X-\mu {)}^2]=E[X^2]-(E[X]{)}^2$
• Equals to Standard deviation squared

Propositions:

• $Var(aX+b)=a^{2}Var(X)$
• If $X_i,...,X_n$ are pairwise independent, then $Var\left(\sum _{i=1}^n{X}_i\right)=\sum _{i=1}^{n}Var(X_i)$

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