1-Assume that the mean hourly cost to operate a commercial airplane follows the normal distribution with a mean of $2,150 per hour and a standard deviation of $200.
What is the operating cost for the lowest 10 percent of the airplanes?
2-The manufacturer of a laser printer reports the mean number of pages a cartridge will print before it needs replacing is 12,325. The distribution of pages printed per cartridge closely follows the normal probability distribution and the standard deviation is 695 pages. The manufacturer wants to provide guidelines to potential customers as to how long they can expect a cartridge to last.
How many pages should the manufacturer advertise for each cartridge if it wants to be correct 95 percent of the time?
3-Dottie's Tax Service specializes in federal tax returns for professional clients, such as physicians, dentists, accountants, and lawyers. A recent audit by the IRS of the returns she prepared indicated that an error was made on 7 percent of the returns she prepared last year. Assuming this rate continues into this year and she prepares 80 returns. What is the probability that she makes errors on: