The inspection crew of a state department of transportation counts the number of potholes per mile on a major highway as part of their quality assurance program. The data below show the number of holes on 32 randomly selected miles. Is the pothole-producing process in-control? In other words, does the incidence of potholes seem to be consistent from mile to mile, or do some miles have significantly more potholes than the others? (The control chart is really a series of significant tests, a test being made each time a sample is collected and checked.) Mile no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 No of potholes 12 8 6 4 2 21 3 2 8 13 25 0 1 5 4 8 Mile no. 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 No. of potholes 11 31 3 0 1 7 0 7 5 2 9 13 0 2 12 15

(a) Calculate the control limits by using a calculator. (b) Construct the control chart by Minitab. (c) Make conclusions and recommendations.