Problem 1. The Watson Electric Company produces incandescent light bulbs. The following data on the number of lumens for 40-watt light bulbs were collected when the process was in control. Sample 1 2 3 4 1 614 602 598 600 2 597 601 590 606 3 581 603 585 599 4 620 605 595 588 5 595 609 608 604
a) (15 points) Calculate the control limits for an R-chart. b) (15 points) Calculate the control limits for an x-bar -chart. c) (10 points) Since these data were collected, some new employees were hired. A new sample obtained the following readings: 575, 603, 623 and 583. Is the process still in control? (hint: use the original sample set as a benchmark to assess the new sample)