A textile manufacturer wants to set up a control chart for irregularities (e.g. oil stains, shop soil, loose threads, and tears) per 100 square yards of carpet. The following data were collected from a sample of twenty l00-square.yard pieces of carpet:

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?

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Sample regularities1 8 9 12 4 16 5 8 17 10 Sample irregularities 11 5 7 12 13 8 19 11 9 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20