Question 1058518: The travel-to-work time for residents of the 22 largest cities in the United States is reported in the
2003 Information Please Almanac. Suppose that a preliminary simple random sample of residents
of San Francisco is used to develop a planning value of 5.95 minutes for the population standard
deviation.
a. If we want to estimate the population mean travel-to-work for San Francisco residents with a
margin of error of 2 minutes, what sample size should be used? Assume 95% confidence.
b. If we want to estimate the population mean travel-to-work for San Francisco residents with a
margin of error of 30 seconds, what sample size should be used? Assume 99% confidence.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! The travel-to-work time for residents of the 22 largest cities in the United States is reported in the 2003 Information Please Almanac. Suppose that a preliminary simple random sample of residents of San Francisco is used to develop a planning value of 5.95 minutes for the population standard
deviation.
a. If we want to estimate the population mean travel-to-work for San Francisco residents with a margin of error of 2 minutes, what sample size should be used? Assume 95% confidence.
Since E = z*s/sqrt(n), n = [z*s/E]^2 = [1.96*5.95/2]^2 = 34
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b. If we want to estimate the population mean travel-to-work for San Francisco residents with a margin of error of 30 seconds, what sample size should be used? Assume 99% confidence.
n = [2.5758*5.95/(1/2)]^2 = 940 when rounded up
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Cheers,
Stan H.
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