Question 1. Passenger comfort is influenced by the amount of pressurization in the airline cabin. Higher pressurization permits a closer-to-normal environment and a more relaxed flight. A study by an airline user group recorded the corresponding air pressure on 30 randomly chosen flights. The study revealed a mean equivalent pressure of 8,000 feet with a standard deviation of 300 feet.
a. Develop a 99% confidence interval for the population mean equivalent pressure.
b. How large a sample is needed to find the population mean within 25 feet at 95% confidence?
Question 2. A sample of 352 subscribers to wired magazine shows the mean time spent using the internet is 13.4 hrs per week, with a sample standard deviation of 6.8 hrs. Find the 95% confidence interval for the mean time wired subscriber spend on the internet.
Question 3. Traditionally, 2% of the citizens of the United States live in a foreign country because they are disenchanted with U.S POLITICS OR SOCIAL attitudes. In order to test if this proportion has increased since the sept.11 2001, terror attacks, u.s consulates contacted a random sample of 400 of these expatriates. The sample yields 12 people who report they are living overseas because of political and social attitudes. Can you conclude this data shows the proportion of politically motivated expatriates has increased? Use the 0.05 significance level.
Question 4. A national grocer's magazine reports the typical shopper spends 8mins in line waiting to check out. A sample of 24 shoppers at the local farmer Jack's showed a mean of 7.5 minutes with a standard deviation of 3.2 mins. Is the waiting time at the local farmer Jack's less than that reported in the national magazine? Use the .05 significance level.