You may need to use the appropriate appendix table or technology to answer this question.

A government agency provides the number of miles that residents of the 75 largest metropolitan areas travel per day in a car. Suppose that for a simple random sample of 50 City A residents the mean is 22.9 miles a day and the standard deviation is 8.7 miles a day, and for an independent simple random sample of 40 City B residents the mean is 18.6 miles a day and the standard deviation is 7.7 miles a day.

(a)

What is the point estimate of the difference between the mean number of miles that City A residents travel per day and the mean number of miles that City B residents travel per day? (Use City A City B.)

__________ mi/day

(b)

What is the 95% confidence interval for the difference between the two population means (in miles per day)? (Use City A City B. Round your answers to one decimal place.)

_______________ mi/day to ___________mi/day