Question

Shaft wear in excess of 3.50 microns could lead to catastrophic failures of a certain model fuel pump in extreme weather conditions. Engineers for the manufacturer of the shafts claim that the shaft wear is within acceptable limits. Lawyers representing a class action legal suit filed against the company feel that recent vehicle failures for vehicles with this shaft are due to faulty bearings causing abnormal wear and, thus, feel that the company should pay for the necessary vehicle repair and parts replacement.

The amount of shaft wear (in microns.) after a simulated mileage of 250,000 miles was determined for each of n = 45 fuel pumps having copper lead as a bearing material, resulting in x̄ = 2.73 and s = 1.25. Use the appropriate hypothesis test at level .01 to determine if the shaft wear is within acceptable limits.  Please state any assumption you have made, if necessary.

Answer 1