Statistical Process Control Methods/ R and x Charts
Watson Electric produces bulbs for emergency flashlights. The following data on the number of lumens (i.e. lumens measure the level of "brightness") for 40-watt bulbs were collected when the process was in control. Observation Sample 1 2 3 4 1 604 612 588 600 2 597 601 607 603 3 581 570 585 592 4 620 605 595