70. A control chart is to be established on a process producing refrigerators. The inspection unit is one refrigerator, and a common chart for nonconformities is to be used. As preliminary data, 16 nonconformities were counted in inspecting 30 refrigerators. (a) What are the three-sigma control limits? (b) What is the -risk for this control chart? (c) What is the -risk if the average number of defects is actually 2 (i.e., if c=2.0 )? (d) Find the average run length if the average number of defects is actually 2