A student referendum is held to determine student opinion about the construction of a recreation complex on campus. Unknown to the administration, 50% of the student body actually favors the construction (F). When the referendum is held, only 40% of the students vote (V). Overall, 32% of student body vote in favor of the construction (V and F). If a student is selected at random from among the student body, what is the probability that he or she either voted or was in favor of the building? Since percentages may be interpreted as being probabilities, we are given that P[F] = .5, P[V] = .4 and P[V and F] = .32. We are asked to find P[V or F]. By the addition rule,
P[V or F] = P[V] + P[F] - P[V and F] = .4 +.5 - .32 = .58