A firm having 4000 employees took a random sample of 25 in order to estimate their average annual state tax payment with 99% confidence. If the results were  x̅ = $640 and s = $20, what is the best interval estimation

What percent of our campus is female? If no preliminary study is made to estimate, how large a sample is needed be 99% sure that the error will be no more than 0.03 from?

A doctor wants to estimate the mean HDL cholesterol of all​ 20- to​ 29-year-old females. How many subjects are needed to estimate the mean HDL cholesterol within 2 points with 99% confidence assuming s=13.4 based on earlier​ studies? Suppose the doctor would be content with 95% confidence. How does the decrease in confidence affect the sample size​ required?

In 2011 the U.S. Department of Transportation reported with 95% confidence that the average length of a motor vehicle trip in the United States was 9.72 miles with a margin or error of 0.22 miles. With 95% confidence the authors of the report are claiming that the true average length of a motor vehicle trip in the United States is between and miles. The level of confidence for this estimate is %.

A hospital administrator wants to estimate the proportion of patients whose hospital stay exceeds a week. How many patients should be sampled to estimate the proportion staying more than a week to within 4 percentage points with 90% confidence?