The mean of a random variable X is also called the expectation of X, denoted by
E(X) Thus,
E (X) = μ =
1
n
i
i
i
x p
  
= x1 p1+ x2 p2 + + xn pn In other words, the mean or expectation of a random variable X is the sum of the
products of all possible values of X by their respective probabilities