A manufacturing company produces valves in various sizes and shapes. One

particular valve plate is supposed to have a tensile strength of 5 pounds per millimeter

(lbs/mm). The company tests a random sample of 42 such valve plates from a lot of 650 valve plates. The sample mean is a tensile strength of 5.0611 lbs/mm, and the

population standard deviation is .2803 lbs/mm. Use a = .10 and test to determine whether the lot of valve plates has an average tensile strength of 5 lbs/mm.