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Hypothesis Testing on Maintenance Costs of Trucks

An Electric Co. Operates a fleet of trucks that provide electrical service to the construction industry. Monthly mean maintenance cost has been $75 per truck. A random sample of 40 trucks provided a sample mean of $82.50 per month, with a sample deviation of $30. Managers want a test to determine whether the mean monthly maintence cost has increased.

A. Using a .05 level of significance, what is the rejection rule for this test?

B. what is your conclusion based on the sample mean of $82.50?

C. what is the p-value associated with the sample result? What is your conclusion based on the p-value?

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