A sample of 40 different payroll departments found that employees worked an average of 240.6 days a year.  If the population standard deviation is 20 days, find the 95% confidence interval for the average number of days μ worked by all employees who are paid through payroll departments.

A Gallup poll of 1487 adults showed that 43% of the respondents have Facebook pages.  Construct a 95% confidence interval for the proportion of adults who have a Facebook page.

In a recent year, a sample of the South American Redeye Piranha was collected by fishermen on a particular river. Wildlife biologists regard this sample as a random sample of all Redeye Piranha in that river. The mean length of the 60 fish in the sample was 12.88 cm, and a 99% confidence level for the true mean length of all Redeye Piranha in that river is 12.09 cm to 13.67 cm.  Explain what would happen to the length of the interval if the confidence level were decreased to 95%.

According to a study of 90 truckers, a trucker drives, on average, 560 miles per day.  If the standard deviation of the miles driven per day for the population of truckers is 40, find the 95% confidence interval of the mean number of miles driven per day by all truckers.

In a random sample of 400 adults in a small town, 189 of them participated in some form of adult education. Find a 98% confidence interval for the population proportion of adults in the town who participate in adult education

A random sample of high school seniors were asked whether they were applying for college. The resulting confidence interval for the proportion of students applying for college is (0.65,0.69). What is the margin of error?

A study of 22 goats reveals that the average length of a goat’s tail is 6.3 inches. If the standarddeviation is known to be 1.2 inches find a 95% confidence interval for the mean tail length.

A sample of 30 Microsoft employees yielded a mean of 44 hours worked per week with a standard deviation of 8 hours. What is the 95% confidence interval on the mean hours worked for Microsoft employees?