Computer upgrades have a nominal listed I time of 80 minutes. Samples of five o

Question

Computer upgrades have a nominal listed I time of 80 minutes. Samples of five o tions each have been taken, and the results are as 79.280.5 79.6 78.9 80.5 79.7 78.8 78.7 79.6 79.4 79.6 80.6 80.0 81. 80.4 79.7 80.4 80.5 78.480.4 80.3 79.4 80.8 8.0 81.080.1 80.8 80.6 78.8 81.1 Factors for three-sigma control limits for and R charts FACTORS FOR R CHARTS Number of observations chart, in Subgroup42 Factor for Control Limit, Control 1.88 1.02 0.73 0.58 0.48 3.27 2.57 2.28 2.11 2.00 1.92 1.86 1.82 1.78 8.08 0.37 0.34 0.31 0.29 0.18 0.22 0.26 10

Explanation / Answer

R

R= 9.5/5= 1.9

UCL= D4*R= 2*1.9=3.8

LCL= D3*R= 0*1.9=0

X-bar

X= 399.8/5= 79.96

UCL= X+A2*R= 79.96+0.48*1.9= 80.872

LCL= X-A2*R= 79.96-0.48*1.9= 79.048

D3, D4 and A2 are for n=6 because we have six sub groups in each sample.

1 2 3 4 5 6 X R 79.2 80.5 79.6 78.9 80.5 79.7 79.73333333 1.6 78.8 78.7 79.6 79.4 79.6 80.6 79.45 1.9 80 81 80.4 79.7 80.4 80.5 80.33333333 1.3 78.4 80.4 80.3 79.4 80.8 80 79.88333333 2.4 81 80.1 80.8 80.6 78.8 81.1 80.4 2.3 X R 79.96 1.9

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