The travel-to-work time for residents of the 15 largest cities in the United Sta

Question

The travel-to-work time for residents of the 15 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 6.01 minutes for the population standard deviation.

1.If we want to estimate the population mean travel-to-work time for San Francisco residents with a margin of error of 5 minutes, what sample size should be used? Assume 95% confidence.

2.If we want to estimate the population mean travel-to-work time for San Francisco residents with a margin of error of 2 minutes, what sample size should be used? Assume 95% confidence.

Explanation / Answer

1. z(0.975) = 1.96

for margin of error 5 min let sample size =n

5= 1.96*6.01/sqrt(n)

n = 6

2.

2= 1.96*6.01/sqrt(n)

n = 35

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