Question 28 3 pts A design engineer wants to construct a mean chart for controlling the service life of a halogen headlamp his company produces. He tested service life on randomly picked three samples with four headlamps each, with these results: sample 1 2 3 5 4 1 800 900 1000 900 800 2 2 900 700 900 900 800 3 800 900 900 1000 1000 4 900 900 900 900 900 What are the x-bar chart upper and lower control limits? 4 972 and 798 994.5 and 777.5 0987.2 and 782.8 1001 and 715