Chapter 6: Q107SE (page 374)
Use Table III, Appendix D to determine the values foreach of the following probability statements and their respectivedegrees of freedom (df ).
a.
b.
c.
d.
Short Answer
a.-0.6912
b.1.39682
c.0.0127
d.0.06337
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Chapter 6: Q107SE (page 374)
Use Table III, Appendix D to determine the values foreach of the following probability statements and their respectivedegrees of freedom (df ).
a.
b.
c.
d.
a.-0.6912
b.1.39682
c.0.0127
d.0.06337
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Accountants鈥 salary survey. Each year, ManagementAccountingreports the results of a salary survey of themembers of the Institute of Management Accountants(IMA). One year, the 2,112 members responding had a salarydistribution with a 20th percentile of \(35,100; a medianof \)50,000; and an 80th percentile of \(73,000.
Lead and copper in drinking water. Periodically, the Hillsborough County (Florida) Water Department tests the drinking water of homeowners for contaminants such as lead and copper. The lead and copper levels in water specimens collected for a sample of 10 residents of the Crystal Lakes Manors subdivision are shown below, followed by a Minitab printout analysing the data.


a. Locate a 90% confidence interval for the mean lead level in water specimens from Crystal Lakes Manors on the printout.
b. Locate a 90% confidence interval on the printout for the mean copper level in water specimens from Crystal Lakes Manors.
c. Interpret the intervals, parts a and b, in the words of the problem.
d. Discuss the meaning of the phrase 鈥90% confident.鈥
Overbooking policies for major airlines.Airlines overbook flights to reduce the odds of flying with unused seats. An article in Transportation Research (Vol. 38, 2002) investigated the optimal overbooking policies for major airlines. One of the variables measured for each airline was the compensation (in dollars) per bumped passenger required to maximize future revenue. Consider the threshold compensation levels for a random sample of major airlines shown in the next table. Estimate the true mean threshold compensation level for all major worldwide airlines using a confidence interval. Interpret the result practically.
825 | 850 | 1,210 | 1,370 | 1,415 |
1,500 | 1,560 | 1,625 | 2,155 | 2,220 |
Hospital length of stay. Health insurers and the federal government are both putting pressure on hospitals to shorten the average length of stay (LOS) of their patients. The average LOS in the United States is 4.5 days (Healthcare Cost and Utilization Project Statistical Brief, October 2014). A random sample of 20 hospitals in one state had a mean LOS of 3.8 days and a standard deviation of 1.2 days.
a. Use a 90% confidence interval to estimate the population's mean LOS for the state鈥檚 hospitals.
b. Interpret the interval in terms of this application.
c. What is meant by the phrase 鈥90% confidence interval鈥?
What is the confidence level of each of the following confidence intervals ?
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