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Determine the critical value of t in each of the following a) 1-a.95,n 10 b) 1-α=.99, n . 10 c) 1-a-.95, n-32 d) 1-as,95, n . 65 e) 1-a-.90, n-16 Homework Problem 8.12 (v5) or None (v7): Southside Hospital in Bay Shore, New York commonly conducts stress tests to study the heat muscle after a person has a heart attack. Members of the diagnostic imaging department conducted a quality improvement project to try to reduce the turnaround time for stress tests. Turnaround time is defined as the time from when the test is ordered to when the radiologist signs off on the test results. Initially, the mean turnaround time for a stress test was 68 hours. After incorporating changes into the stress-test process, the quality improvement team collected a sample of 50 turnaround times. In this sample the mean turnaround time was 32 hours, with a standard deviation of 9 hours a) Construct a 95% confidence interval estimate for the population mean turnaround time. b) Interpret the interval constructed in (a). c) Do you think the quality improvement project was a success? Explain. View as Text
Homework Problem 8.13 (v5) or 8.17 (v7): The U.S. Department of Transportation requires tire manufacturers to provide tire performance information on the sidewall of a tire to better inform prospective customers as they make purchasing decisions. One very important measure of tire performance is the tread wear index, which indicates the tires resistance to tread wear compared with a tire graded with a base of 100. A tire with a grade of 200 should last twice as long, on average, as a tire graded with a base of 100. A consumer organization wants to estimate the actual tread wear index of a brand name of tires that claims graded 200 on the sidewall of the tire. A random sample of n 18 indicates a sample mean tread wear index of 195.3 and a sample standard deviation of 21.4. a) Assuming that the population of tread wear indexes is normally distributed, construct a 95% confidence interval estimate for the population mean tread wear index for tires produced by this manufacturer under this brand name. (Also, include the INTERPRETATION). b) Do you think that the consumer organization should accuse the manufacturer of producing tires that do not meet the performance information provided on the sidewall of the tire? Explain. c) Explain why an observed tread wear index of 210 for a particular tire is not unusual, even though it is outside the confidence interval developed in (a). 42 2 View as Text
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Finding the t critical values using t tables

,05,9 . 1-833 ,05,31= D5, 6406290 1o66

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