Probability

$E(X) = \overline{x} = \mu$

$Var(X) = E(X^2) - (E(x))^2$

$\therefore E(X^2) = Var(X) + (E(X))^2$

Law of Large Numbers

Whatever the setup as the number of trials increases the observed probability will approach the theoretical probability

e.g. The more coin tosses you do the more the observed number of heads will approach 50% of the total amount of coin flips