QUESTION 4 A design engineer wants to construct a sample mean chart for controlling the service life of a halogen headlamp his company produces. He knows from numerous previous samples that when this service life is in control it is normally distributed with a mean of 500 hours and a standard deviation of 20 hours. On three recent production butches, ho tested service life on random samples of four headlamps, with these results: Compute the Upper Control Limit for the Range chart Sample 1 2 3 490 520 475 Service Life Chours) 500 500 515 530 480 490 500 SIS 470 51 hours 474 hours 49 hours 44 hours 34 hours