Answer to Question #26079 in Microeconomics for lee

Question

Past data have shown that if the payphones at the airport are emptied every 14 days, the coin collectors will be 70% full on the average. The phone company tries to schedule the collection visits at 70% full because money is lost if the phones get full and unusable, but visiting the phones too frequently is also an expense. The company keeps data on fill amounts during collection, in case they need to increase or decrease collection frequency. During the last visit, suppose that 5 phones were 50%, 40%, 70%, 75%, and 45% full, respectively. Do you think the frequency of visits needs to be changed, or is this just chance variation?