Cafe Mamak has been receiving complaints from its loyal customers concerning the inconsistent quality of their roti bakar over the past few months. The manager had collected some data concerning the types of quality issues concerning their roti bakar over the past month: Sample 1 Defect Type A Worker Sample Defect Type Time Sample Defect Type Worker X 2 D Y 3 D Y 4 D Y 5 C X 6 C Y 7 C Z 8 A X 9 B X 10 D Y 11 E X 12 D Y 13 C W 14 C Y 15 Y 122222222222222 16 A X 31 A W 17 A X 32 A X 18 B Z 33 A X B Z 34 B Y B Y 35 B Y B X 36 B W E X 37 D Y D Z 38 E X D Z 39 D Y D W 40 D X D X 41 D Y 27 D Y 42 D Y C W 43 A X D Y 44 A X D Y 45 A W