1. A random sample of 15 telephone calls in an office showed the duration of each...

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1. A random sample of 15 telephone calls in an office showed the duration of each call and whether it was a local or a long distance call. Call Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Duration (In Minutes) 2 12 10 3 5 6 3 5 8 4 5 4 5 4 9 Type of Call local long distance local local long distance local local local local local local local local local long distance a. What is the point estimate for the average duration of all calls? b. What is the point estimate for the standard deviation of the population? C. What is the point estimate for the proportion of all calls that were long distance? 2. In order to determine the average weight of carry-on luggage by passengers in airplanes, a sample of 16 pieces of carry-on luggage was weighed. The average weight was 20 pounds. Assume that we know the standard deviation of the population to be 8 pounds. a. Determine a 97% confidence interval estimate for the mean weight of the carry- on luggage. (5) 3. A tire manufacturer has been producing tires with an average life expectancy of 26,000 miles. Now the company is advertising that its new tires' life expectancy has increased. In order to test the legitimacy of the advertising campaign, an independent testing agency tested a sample of 6 of their tires and has provided the following data. Life Expectancy (In Thousands of Miles) 28 27 25 28 29 25 a. Determine the mean and the standard deviation. (5) b. At 99% confidence using the critical value approach, test to determine whether or not the tire company is using legitimate advertising. Assume the population is normally distributed. (10) ~THE END~ TOTAL: 30 1. A random sample of 15 telephone calls in an office showed the duration of each call and whether it was a local or a long distance call. Call Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Duration (In Minutes) 2 12 10 3 5 6 3 5 8 4 5 4 5 4 9 Type of Call local long distance local local long distance local local local local local local local local local long distance a. What is the point estimate for the average duration of all calls? b. What is the point estimate for the standard deviation of the population? C. What is the point estimate for the proportion of all calls that were long distance? 2. In order to determine the average weight of carry-on luggage by passengers in airplanes, a sample of 16 pieces of carry-on luggage was weighed. The average weight was 20 pounds. Assume that we know the standard deviation of the population to be 8 pounds. a. Determine a 97% confidence interval estimate for the mean weight of the carry- on luggage. (5) 3. A tire manufacturer has been producing tires with an average life expectancy of 26,000 miles. Now the company is advertising that its new tires' life expectancy has increased. In order to test the legitimacy of the advertising campaign, an independent testing agency tested a sample of 6 of their tires and has provided the following data. Life Expectancy (In Thousands of Miles) 28 27 25 28 29 25 a. Determine the mean and the standard deviation. (5) b. At 99% confidence using the critical value approach, test to determine whether or not the tire company is using legitimate advertising. Assume the population is normally distributed. (10) ~THE END~ TOTAL: 30

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