Hypothesis Testing: t tests. Onyx Corporation designs and manufactures a broad range of fluid-handling and industrial products. Although fluid-handling products have been a rapidly growing market for Onyx during recent years, operating margins dipped recently as customers have complained about lower reliability for one of the company€™s principal products. Indeed, one of its leading customers provided Onyx with 2 years of data on the customer€™s downtime experience:

A. Calculate the 95 percent confidence interval for the population mean downtime for each of the 2 years.

B. At this confidence level, is it possible to reject the hypothesis that downtime experience is the same during each of these 2 years?

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Onyx Corp. Hours of Downtime per Month Month Last Year This Year January February March 5 April May June Onyx Corp. Hours of Downtime per Month Month Last Year This Year August 5 September 5 October November 5 December