Notation

Description	Example	Meaning
E function	$E(Y)$	Expected (mean) value
Var function	$Var(Y)$	Variance of a random variable
Subscript	$E_{Y|X=x}(Y)$ $E_{Y|x}(Y)$ $E_Y(Y|X = x)$	Indicate the distribution used to compute the parameters. In this example, the equation represents the mean of $Y$ given that random variable $X$ assumes the value of $x$