A metropolitan transportation authority has set a bus mechanical reliability goal of 3,700 bus miles. Bus mechanical reliability is measured specifically as the number of bus miles between mechanical road calls. Suppose a sample of 100 buses resulted in a sample mean of 3,750 bus miles and a sample standard deviation of 275 bus miles. What are the critical value(s) for the test statistic?
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A. A metropolitan transportation authority has set a bus mechanical reliability goal of 3,700 bus miles. Bus mechanical reliability is measured specifically as the number of bus miles between mechanical road calls. Suppose a sample of 100 buses resulted in a sample mean of 3,750 bus miles and a sample standard deviation of 275 bus miles. What are the critical value(s) for the test statistic?
B. A report states that the cost of repairing a hybrid vehicle is falling even while typical repairs on conventional vehicles are getting more expensive. The most common hybrid repair, replacing the hybrid inverter assembly, had a mean repair cost of $3,927 in 2012. Industry experts suspect that the cost will continue to decrease given the increase in the number of technicians who have gained expertise on fixing gas-electric engines in recent months. Suppose a sample of 100 hybrid inverter assembly repairs completed in the last month was selected. The sample mean repair cost was $3,750 with the sample standard deviation of $600. What are the critical value(s) for the test statistic?
C. The worldwide market share for a web browser was 20.4% in a recent month. Suppose that a sample of 200 random students at a certain university finds that 50 use the browser. Suppose that a sample of n=800 students at the same university (instead of n=200) determines that 25% of the sample use the web browser. At the 0.05 level of significance, is there evidence that the market share for the web browser at the university is greater than the worldwide market share of 20.4%? Calculate the test statistic for the second sample. What is the p-value? State the conclusion of the test.
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