The data processing department of the Arizona Bank has five data entry clerks. Each working day their supervisor verifies the accuracy of a random sample of 250 records. A record containing one or more errors is considered defective and must be redone. The results of the last 30 samples are shown in the table. All were checked to make sure that none was out of control.

a. Based on these historical data, set up a p-chart using z = 3.
b. Samples for the next 4 days showed the following:

What is the supervisor’s assessment of the data entry process likely to be?

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Sample 1 2 3 4 5 6 7 8 Number of Defective Records 7 5 19 10 11 8 12 9 Sample 9 10 11 12 13 14 15 16 Number of Defective Records 6 13 18 5 16 4 11 8 Sample 17 18 19 20 21 22 23 Number of Defective Records 12 4 6 11 17 12 6 Sample 24 25 26 27 28 29 30 Total Number of Defective Records 7 13 10 14 6 11 9 300