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In many rural areas, newspaper carriers deliver morning papers using their automobiles because the length of the route prohibits walking

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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  ? = 16.7 mi with s = 3.4 mi.
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.
If the mean length of the routes is more than 20 mi, 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 that the true mean route length is more than 20 mi? Justify your answer.