Question

Special Plastics, Inc. has been making the blanks for credit cards for a number of years. They use p charts to keep track of the number of nonconforming cards that are created each time a batch of blank cards is run. Use the following data to create a fraction nonconforming chart (p-chart).

Sample	n	y	p
1	900	40
2	900	41
3	900	38
4	900	30
5	900	36
6	900	38
7	900	18
8	900	20
9	900	22
10	900	50

Answer 1

Sample	n	y	p
1	900	40	0.044444
2	900	41	0.045556
3	900	38	0.042222
4	900	30	0.033333
5	900	36	0.04
6	900	38	0.042222
7	900	18	0.02
8	900	20	0.022222
9	900	22	0.024444
10	900	50	0.055556

The p-chart is:

The process is in control.

The control limits are:

Sample size	900
Number of samples	10
	Proportion defective
Upper Control Limit, UCL	0.0559
Center	0.0370
Lower Control Limit, LCL	0.0181