Expected value = E(x) = x1P1+x2P2+ ... + xnPn Where x = the outcome and P = probability of outcome Dr. Kimball likes to go fishing with his son. To motivate his son, he pays him for the first fish that he catches. There are two types of edible fish that his son can catch: Trout and Salmon.  If he catches a Trout he pays him $5, if he catches Salmon $3. There is a 20% chance that he will catch a trout and 50% that he will catch a Salmon.