Answer Happy

(b) Printed circuit boards for a mobile phone are produced by an etch-resist printing process, the exposed copper is acid-etched away, leaving the circuit-board ready for population with components. Because the acid-etch process is expensive, the boards are inspected for print defects after the printing process, but before etching. Any defective boards are rejected and reprocessed. Table Q1 shows the number of boards produced and defective boards found each day for 20 days of production. Day Day Number of Number of Number of Boards Number of Defective Boards Defective Produced Boards Produced Boards 1 1047 62 11 1497 99 2 950 48 1851 153 12 13 3 1201 85 1452 87 4 1388 103 14 1347 108 5 1164 93 15 1066 80 6 1502 126 16 263 29 7 1871 153 17 1180 72 8 493 27 18 784 18 9 826 37 19 1258 71 10 1478 104 20 1726 135 Table Q1[b) Daily Production and Number of Defective Printed Boards (0) Name and briefly describe the four main types of attribute control charts. (4 marks) (11) Which type of attribute control chart should be used in this case? [2 marks]
(HH) Calculate the upper and lower control limits of a suitable attribute control chart for the data. (Upper and Lower Control limits for attribute charts are given in the Appendix) and plot the chart. Thus explain whether or not the process is in control. [14 marks]