A manufacturer of band saws wants to estimate the average repair cost per month for the saws he has sold to certain industries. He cannot obtain a repair cost for each saw, but he can obtain the total amount spent for saw repairs and the number of saws owned by each industry. Thus, he decides to use cluster sampling, with each industry as a cluster. The manufacturer selects a simple random sample of n = 20 from the N = 96 industries he services. The data on total cost of repairs per industry' and number of saws per industry' are as given in the accompanying table. (a) Estimate the average repair cost per saw for the past month and place a bound on the error of estimation.
(b) Estimate the total amount spent by the 96 industries on band saw repairs. Place a bound on the error of estimation.
(c) After checking his sales records, the manufacturer finds that he sold a total of 710 band saws to these industries. Using this additional information, estimate the total amount spent on saw repairs by these industries and place a bound on the error of estimation.