Many companies are increasingly concerned about computer security and employees using their computers for personal use. A random sample of 50 employees of Liberty Mutual Insurance Company was asked whether they use the Internet for nonbusiness (personal) purposes during the day. The number of hours for each employee is given on the text website. Assume s 5 0.5 hours. INTERNET
a. Find a 95% confidence interval for the mean number of hours all employees at Liberty Mutual use the Internet for personal reasons.
b. Using the confidence interval in part (a), is there any evidence to suggest that the mean time spent using the Internet for personal reasons is more than 1 hour? Justify your answer.
c. How large a sample is necessary for the bound on the error of estimation to be 0.1 hours? d. Do you think the underlying distribution of time spent on the Internet for personal use is normal? Explain your answer.
A random sample of professional wrestlers was obtained, and the annual salary (in dollars) for each was recorded. The summary statistics were
and n = 18. Assume the distribution of annual salary is normal with
a. Find a 90% confidence interval for the true mean annual salary for all professional wrestlers.
b. How large a sample is necessary for the bound on the error of estimation to be 3000?
c. How large a sample is necessary for the bound on the error of estimation to be 1000?
The Boeing 747-8 is a technologically advanced aircraft with a new wing design and GEnx-2B engines, and is capable of holding more passengers and payload than previous versions of the 747. In addition, this plane has better fuel efficiency than the 747-400 and the A380, which means lower carbon emissions.12 A random sample of twelve 747-8 test flights was obtained and the carbon emission was measured on each (in grams CO2 per seat-km). The sample mean was 72. Assume the carbon emission distribution is normal and
a. Find a 99% confidence interval for the true mean carbon emission of all 747-8 planes.
b. The carbon emission for the A380 is 80 g CO2 per seat-km. Is there any evidence to suggest that the mean carbon emission for the 747-8 is lower than that of the A380? Justify your answer.