Another consumer agency tests (in exactly the same manner) tires from the same batch of tires tested by the agency in Problem 20. It randomly selects 25 tires and obtains X 82,200 and sX 900.
(a) Calculate t.
(b) What does the second consumer agency conclude ( .05)?
(c) The mean mileage in the second test was less than in the first. How do you account for the different conclusions?