Determine whether process is under control:
Hall's refrigeration and heating company is concerned about complaints from their customers about some of their technicians. Because of this, the owner has authorized a quality control study to be conducted. Each week, a sample of 100 customers is questioned on their feelings towards their service. For eight weeks, the following number of complaints are made: 10, 8, 18, 6, 4, 17, 8, 10.
a. In this case, what control chart is best to determine whether this process is under control?
b. Use a 3 sigma control chart to determine upper and lower control limits for this process.
c. Is this process under control? Explain (a simple yes or no will not suffice).