Jack Joyner, Director of Quality Control at Covington Castings (CC), is designing a c chart to monitor the number of nonconformances per aluminum casting produced at CC.The total number of nonconformances for 26 castings is 91.The upper control limit for Jack's c chart is ___________.
A)9.11
B)13.40
C)3.50
D)7.61
E)1.00

Question

Quizplus · Accepted Answer

The upper control limit (UCL) for a c chart is calculated using the formula UCL = $ \bar{c} + 3\sqrt{\bar{c}} $, where $ \bar{c} $ is the average number of nonconformances per item. Given 91 nonconformances for 26 castings, $ \bar{c} = \frac{91}{26} = 3.5 $. Thus, UCL = $ 3.5 + 3\sqrt{3.5} \approx 9.11 $.