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

4 620 605 595 588

5 590 614 608 604

a. Assuming 5 samples is sufficient, develop the appropriate control chart(s) and identify the upper and lower control limit(s)

b. Plot your observations on the control chart and draw some conclusions about your results.

c. After the original data was collected, some new employees were hired. A new sample with the following readings was obtained: 570, 603, 623, and 583. Is the process still in control?