The mean or _expected value of a discrete random variable refers to the long-run average value of the random process if it is repeated indefinitely under identical conditions. It is a weighted average of the possible values the random variable can take. The mean of a random variable weights each outcome , according to its probability, .The symbol for the mean (also known as the expected value of ) is or .Use the definition for expected value shown in the margin to calculate the (theoretical) expected value E(G) of the number of green lights that Nicholas encounters on his morning drive to school