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 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
Irregularities 11 5 7 12 13 8 19 11 9 10
Using the above data, set up the appropriate control chart using 3-sigma limits and determine if the process is in control. Also plot the chart.