# View the step-by-step solution to: The U.S. Department of Transportation reported the number of

The U.S. Department of Transportation reported the number of miles that residents of metropolitan areas travel per day in a car. Suppose a simple random sample of 15 residents of Detroit provided the following data on car miles per day.

20 20 28 16 11 17 23 16 22 18 10 22 29 19 32

A) Compute a 95% confidence interval estimate for the population mean number of miles that residents of Detroit travel per day in a car.
B) What assumption must you make in order to calculate the confidence interval in part A?
C) Suppose it is desired to estimate the population mean number of miles with a margin of error of ± 2 miles at 95% confidence. Do the data provide this desired level of precision? What action, if any, would you recommend be taken?

n = 15
x = 20, 20, 28,16,11,17, 23,16, 22,18,10, 22, 29,19,32

20 + 20 + 28 + 16 + 11 + 17 + 23 + 16 + 22 + 18 + 10 + 22 + 29 + 19 + 32
15
⇒ x = 20.2
⇒x=

n

Sample variance, s 2 =

∑ ( x −...

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