Q6 (a) Differentiate between Quality Control and Quality Assurance. Support your comparison with suitable explanation. (4 marks) (b) Table 7 shows the lengths for circuit board manufactured in Albina company. Solve the average and range for subgroup 20, 21, 22, 23, 24 and 25. Use three decimal points. (3 marks) Determine upper and lower control limits for X chart. Use the information in Table 8 to compute the control chart limits. (7 marks) (111) Construct X control chart. (4 marks) (iv) Based on Q6(b)(111), evaluate whether the process is in control. Justify your answer. (2 marks) Subgroup Number Table 7: Circuit board lengths Lengths X2 X3 X4 Xs X1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Average X 5.010 5.001 5.008 5.003 5.003 4.996 5.000 4.997 5.005 4.998 4.994 5.001 4.998 4.990 5.006 4.997 5.001 5.007 4.998 Range R 0.038 0.019 0.036 0.022 0.026 0.024 0.012 0.030 0.014 0.017 0.008 0.011 0.029 0.039 0.016 0.021 0.026 0.018 0.021 5.000 4.988 5.004 5.010 5.015 4.982 5.010 5.001 4.999 4.989 5.008 4.984 5.013 5.009 4.990 4.990 4.993 4.995 5.020 5.005 5.006 5.009 5.000 5.017 5.003 4.996 5.009 5.014 5.010 5.013 Table 8. Factors for calculating X and R control charts Size of sample (n) Factor for UCL and LCL for X-charts (A2) 1.880 Factor for LCL for R-charts (D3) 0 Factor for UCL for R-charts (DA) 3.267 2.574 2 3 1.023 0 4 0.729 0 2.282 5 0.577 0 2.114 6 0 2.004 0.483 0.419 7 0.076 1.924 8 0.373 0.136 1.864 9 0.337 0.184 1.816 10 0.308 0.223 1.777