A textile manufacturer wants to set up a control chart for irregularities per 100 square yards of carpet. The following data were collected from a sample of twenty 100-square-yard pieces of carpet:
Sample : 1 2 3 4 5 6 7 8 9 10
Irregularities : 11 8 9 12 4 16 5 8 17 10
Sample : 11 12 13 14 15 16 17 18 19 20
Irregulaties: 11 5 7 12 13 8 19 11 9 10
a) Using these data, set up a c-chart with z= 3.
b) Suppose that the next five samples had 15, 18, 12, 22, and 21 irregularities. What do you conclude?