An automobile dealer wants to estimate the mean mileage of these vehicles. Previous experience suggests that the population standard deviation is likely to be about 12,000 miles. If a 90% confidence interval for the population mean is to extend 2,000 miles on each side of the sample mean, how large of a sample is required if simple random sampling is employed?
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In this case, the desired level of confidence is 90%. This means that we want to be 90% confident that the true population mean falls within our confidence interval. Show more…
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An automobile dealer has an inventory of 328 used cars. The mean mileage of these vehicles is to be estimated. Previous experience suggests that the population standard deviation is likely to be about 12,000 miles. If a $90 \%$ confidence interval for the population mean is to extend 2,000 miles on each side of the sample mean, how large of a sample is required if simple random sampling is employed?
An automobile dealer has an inventory of 400 used cars. To estimate the mean mileage of this inventory, she intends to take a simple random sample of used cars. Previous studies suggest that the population standard deviation is 10,000 miles. A $90 \%$ confidence interval for the population mean must extend 2,000 miles on each side of its sample estimate. How large of a sample size is necessary to satisfy this requirement?
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