A hospital administrator wishes to determine the mean number of admissions per day to within \(\pm 0.15\) at a 94% confidence level. What sample size should be chosen if it is known that the standard deviation is 0.56?

A survey is to be taken to estimate the proportion of voters who favor stem cell research. Among the following proposed sample sizes, which is the smallest that will still guarantee a margin of error of at most 0.045 for a 98% confidence interval?

Which of the following would result in the narrowest confidence interval?

A researcher plans to investigate the difference between the proportion of children of drug abusers and the proportion of children of nondrug abusers who experiment with drugs while in high school. Which of the following will give the sample size \(n\) that should be taken (same number for each group) to be 95 percent certain of knowing the difference to within ±0.025?

A concerned-scientists action group wishes to learn the proportion of high school students who believe that humans are the principal cause of observed global warming. From a past study, the group knows that it will have to poll 200 people for the desired level of confidence. If the group wants to keep the same level of confidence but divide the margin of error by 3, how many people will it have to poll?

A guidance counselor wishes to know the difference in GPAs between students who exercise regularly and those who don't. Suppose the standard deviation of each group is known to be 0.93. Which of the following will give the sample size \(n\) that should be taken (same number for each group) to be 99 percent certain of knowing the difference to within ±0.1 on the GPA scale?

Two samples, S and T, of sizes 50 and 200, respectively, are obtained from the same population and result in the same sample proportion. In calculating a confidence interval for \(p\) from each sample, which of the following is a true statement about the margins of error obtained for each confidence interval?

The presence of mercury in fish is a growing concern, especially now that people are being encouraged to eat more fish for the omega-3 content. Past studies of New Jersey coastal fish indicated mercury above 0.5 parts per million, a level that could pose a human health concern. A new study is being planned. Assuming the old study's standard deviation of 0.1 parts per million is still accurate, what size sample of fish should be caught for a 95% confidence interval for mercury with a margin of error no more than 0.008 parts per million?

An administrator at the National Council of Teachers is interested in the proportion of teachers who believe they will be able to retire comfortably when they reach the age of 60. Which of the following will give the minimum sample size that needs to be surveyed to be 98 percent confident of the true proportion to within ±3.5 percent?

How fast can you download movies? We want to estimate the mean download time of new software being heavily advertised. Suppose the standard deviation of download times is known to be approximately 8 minutes. Which of the following gives the number of trial downloads we should run to have 90 percent confidence in our answer with a margin of error of at most 5 minutes?

A cardiologist notices that 20 percent of her patients who complain of chest pain need stents. She plans to establish a confidence interval estimate at the 96 percent level with a margin of error of 3 percent. Of the following, which is the smallest sample size that she can use?