Q7

1. An economics professor randomly selected 100 millionaires in the U.S. The average age of these millionaires was 52.10 years with a standard deviation of 12.30 years. Find the 95% confidence interval for the mean age, , of all U.S. millionaires?

2. A lawyer researched the average number of years served by 40 different justices on the Supreme Court. The average number of years served was 14.80 years with a standard deviation of 7.80 years. What is the 99% confidence interval for the average number of years served by all Supreme Court justices?

3. A sample of 36 different payroll departments found that the employees worked an average of 242.50 days a year with a standard deviation of 21.20 days. What is the 90% confidence interval for the average days worked, , of all payroll departments?

4. The average cost of living for a family of 4 in twelve different cities was found to be $65,351.00 with a standard deviation of $7711.00. What is the 90% confidence interval for the true mean?

5. The base salaries of the nine highest paid basketball players was reported to be $7.45 million with a standard deviation of $2.83 million. What is the 90% confidence interval for the true mean?

6. The following list is a sampling of the costs of various statistics textbooks used at several colleges. Give the 95% confidence interval estimate for the mean cost of all statistics textbooks.

109.95

92

96.7

84.85

92.6

84.45

90.95

77

75.5

1. The average daily high temperature during the winter months in the Midwest is to be estimated with a confidence of 98%. How many days must you measure the high temperature in order to be within 3 degrees? Assume the population of temperatures has a standard deviation of 7.18 degrees.

2. Find the Margin of Error(also called Maximum Error of Estimate) that would give the following confidence interval.

37.46