The performance ratings of two sports cars, the Mazda RX7 and the Nissan 300ZX, are to be compared. A random sample of 30 drivers is selected to drive the two models. Each driver tries one car of each model, and the 30 cars of each model are chosen randomly (i.e. we can assume a completely randomized design). The time of each test drive is recorded for each driver and model. The difference in time (Mazda time - Nissan time) is computed for each driver. From these differences a sample mean and sample standard deviation are obtained. The results are Dbar = 1.0 seconds and sD = 2.1 seconds. Based on these data does the Mazda seem to have better performance? Explain. Also give a 90% confidence interval for the average time difference, in seconds, for the two models over the course driven.