During a 4-week inspection period, the number of defects found in a sample of 500 electronic components are listed in the table, below. Construct a c chart for these data. Does it appear as though there existed an assignable cause of variation during the inspection period? Date 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Defects 6 7 10 7 9 17 3 5 3 7 6 4 8 7 8 20 9 10 4 6