$\forall$$p$:FinProbSpace, $a$:$\mathbb{Q}$, $n$:$\mathbb{N}$, $X$:RandomVariable($p$;$n$).
\\[0ex]($\forall$$s$:(\{0..$n$$^{-}$\}$\rightarrow$Outcome). $X$($s$) = $a$) $\Rightarrow$ (E($n$;$X$) = $a$)