Question

15-8. + The copper content of a plating bath is measured three times per day, and the results are reported in ppm. The and r values for 25 days are shown in the following table: Day Day 1 5.45 1.21 147.01 2 5.39 0.95 15 5.83 3 6.85 1.43 16 6.35 1.29 17 6.05 5 5.83 1.35 18 7.11 6 7.22 0.88 19 7.32 7 6.39 0.9220 5.90 8 6.50 1.13 5.50 9 7.15 1.25 6.32 10 5.921.05 236 .55 11 6.45 0.98 24 5.90 125.38 1.36 25 5.95 13 6.03 0.83 1 1.45 1.37 1.04 0.83 1.35 1.09 1.22 0.98 1.21 0.76 1.20 1.19 (a) Using all the data, find trial control limits for X and I charts, construct the chart, and plot the data. Is the process in statistical control?

Answer 1

The control chart is:

Xbar-R Chart VCL-6.5797 Sample Mean X=62836 Ct=5.9875 Sample UCL-2.989 R=194 Sample Range tCt=0.891; Sample

The process is in control.