Question

Surface finish data of the front bumper for passenger vehicle is listed below. First, decide which control chart should be used and then determine the trial control limits and revised control limits. Assume any out- of-control points have assignable causes.

      Lot Number                                  Sample Size                                 Nonconformities  

               1                                                   10                                                     45

               2                                                   10                                                     51

               3                                                    9                                                      36

               4                                                   12                                                     25

               5                                                   11                                                     26

Answer 1

Sample size	52
Number of samples	5
	Proportion defective
Upper Control Limit, UCL	0.8938
Center	0.7038
Lower Control Limit, LCL	0.5139

The control chart is:

The revised control limits are:

Sample size	52
Number of samples	5
	Proportion defective
Upper Control Limit, UCL	0.8779
Center	0.6846
Lower Control Limit, LCL	0.4913

The control chart is: