A random study reported that 80% of very-low-birth-weight babies graduate from high school by age 20. If 280 very-low-birth-weight babies are followed through high school, how many would you expect to graduate from high school?
Recall that if a random variable x can take on the n values x1,x2…..,xn and the probabilities that these values occur are, respectively, p1,p2,….,pn, then the expected of the random variable is E(x) = x1p1+x2p2 + …..xnpn.
(0.80)(280) = 224
Therefore , it is expected that 224 out of 280 very-low-birth-weight babies will graduate high school by the age of 20.