Fuel Consumption and Cars In many rural areas, newspaper carriers deliver morning papers using their automobiles because the length of the route prohibits walking. In a random sample of 28 carriers who use their automobiles, the sample mean route length was x‾= 16.7 miles with σ = 3.4.
a. If the distribution of route lengths is normal, find a 95% confidence interval for the true mean route length of newspaper carriers who use their automobiles.
b. If the mean length of the routes is over 20 miles, the circulation department becomes concerned that papers will not be delivered by 7:00 a.m. Using your answer to part (a), is there any evidence to suggest the true mean route length is over 20 miles? Justify your answer. Write a Solution Trail for this problem.