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 Example 27 Let a pair of dice be thrown and the random variable X be the sum of the
numbers that appear on the two dice