Fast-food restaurants spend quite a bit of time studying the amount of time cars spend in their drive throughs. Certainly the faster the cars get through the drive through, the more opportunity for making money. QSR magazine studied drive through times for fast-food restaurants and found Wendy's has the best time, with a mean time spent in the drive through of mu=138.5 second. Assuming drive through times are normally distributed with a standard deviation of 29 seconds, answer the following:
(a) What is the probability that a randomly selected car will get through the Wendy's drive through in less than 100 seconds, P(X<100)?
(b) What is the probababily that a car will spend more than 160 seconds in the Wendy's drive through, P(X>160)?
(c) According to our normal model, what is the probababily that a car will spend less than 4 minutes in the Wendy's drive through P(X<240)? (Note: you will not be able to get me a precise value for this probability using the table, but you can tell me what is has to be greater than.)
(d) Would you say that it is unusual for a car to spend more than 4 minutes in the Wendy's drive through? Why?