If 20 samples of a production process are taken and there are 240 total defects,the upper and lower control limits for a 3-sigma c-chart are
A)UCL = 16.472,LCL = 7.528
B)UCL = 15.464,LCL = 8.536
C)UCL = 22.392,LCL = 1.608
D)UCL = 18.728,LCL = 5.272

Question

Quizplus · Accepted Answer

The average number of defects per sample is calculated as total defects divided by the number of samples, which is 240/20 = 12. For a c-chart, the control limits are calculated using the formula: UCL = $ \bar{c} + 3\sqrt{\bar{c}} $ and LCL = $ \bar{c} - 3\sqrt{\bar{c}} $, where $ \bar{c} $ is the average number of defects. Substituting $ \bar{c} = 12 $, we get UCL = 12 + 3√12 ≈ 22.392 and LCL = 12 - 3√12 ≈ 1.608.

If 20 Samples of a Production Process Are Taken and There