• • S6.18 Five data entry operators work at the data processing department of the Birmingham Bank. Each day for 30 days, the number of defective records in a sample of 250 records typed by these operators has been noted, as follows:

a) Establish 3s upper and lower control limits.

b) Why can the lower control limit not be a negative number?

c) The industry standards for the upper and lower control limits are 0.10 and 0.01, respectively. What does this imply about Birmingham Bank’s own standards?

SAMPLE NO. NO. SAMPLE DEFECTIVE NO. NO. DEFECTIVE SAMPLE NO. NO. DEFECTIVE 1 7 11 18 21 17 23 5 12 5 22 12 19 13 16 23 6 4565% o 10 14 4 24 7 11 15 11 25 13 8 16 8 26 10 7 12 17 12 27 14 8 9 18 4 28 6 9 6 19 6 29 12 10 13 20 16 30 3