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# Chapter 7 - Question 1 2 out of 2 points A sample of 25...

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Question 1 2 out of 2 points A sample of 25 different payroll departments found that the employees worked an average of 310.3 days a year with a standard deviation of 23.8 days. What is the 90% confidence interval for the average days worked, , of all payroll departments? Answer Selected Answer: Correct Answer: Question 2 2 out of 2 points

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A previous study of nickels showed that the the standard deviation of the weight of nickels is 200 milligrams. A coin counter manufacturer wishes to find the 99% confidence interval for the average weight of a nickel. How many nickels does he need to weigh to be accurate within 20 milligrams? Answer Selected Answer: 664 Correct Answer: 664 Question 3 2 out of 2 points Jennifer wants to find a 95% confidence interval for the time it takes her to get to work. She kept records for 30 days and found her average time to commute to work was 20.5 minutes with a standard deviation of 3.9 minutes. Jennifer's maximum error of estimate would be 1.4 minutes. Answer
Selected Answer: True Correct Answer: True Question 4 2 out of 2 points A researcher conducted a study of the access speed of 45 hard drives and concluded that his maximum error of estimate was 20. If he were to conduct a second study to reduce the maximum error of estimate to 5, about how many hard drives should he include in his new sample? Answer Selected Answer: 720 Correct Answer: 720

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Question 5 2 out of 2 points When computing a confidence interval for a population mean using raw data, round off to two more decimal places than the number of decimal places in the original data. Answer Selected Answer: False Correct Answer: False Question 1 0 out of 2 points A food snack manufacturer samples 9 bags of pretzels off the assembly line and weighed their contents. If the sample mean is 9.8 and the sample standard deviation is 0.10, find the 95% confidence interval of the true mean. Answer
Selected Answer: [None Given] Correct Answer: (9.72, 9.88) Question 2 0 out of 2 points In a study of size 12 where the variance is unknown, the distribution that should be used to calculate confidence intervals is Answer

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Selected Answer: [None Given] Correct Answer: a t distribution with 11 degrees of freedom Question 3 0 out of 2 points Find the 95% confidence interval for the variance of the heights of maple trees if a sample of 21 trees has a standard deviation of 10 feet. Answer
[None Given] Correct Answer: 58.5 < < 208.5 Question 4 0 out of 2 points A study of peach trees showed that the average number of peaches per tree was 1000. The standard deviation of the population is 100. A scientist wishes to find the 98% confidence interval for the mean number of peaches per tree. How many trees does she need to sample to be accurate within 10 peaches per tree? Answer

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Chapter 7 - Question 1 2 out of 2 points A sample of 25...

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