A cell phone company is trying to improve customer service through a reduction in billing errors. The billing department monitors its billing process by taking daily samples of 150 customer bills for 8 days and checking their accuracy. The sample results are shown below. Construct a control chart to help the phone company monitor the fraction of bills with error. Plot samples 1, 2, 3 on the chart.

Sample	1	2	3	4	5	6	7	8
Number of bills that had an error	8	12	6	5	12	8	11	4