In an issue of Quality Progress, Gunter presents several control charts. Four of these charts are reproduced in Figure 16.17. For each chart, find any evidence of a lack of statistical control (that is, for each chart identify any evidence of the existence of one or more assignable causes). In each case, if such evidence exists, clearly explain why the plot points indicate that the process is not in control.

Figure 16.17

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d.

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UCL = 5.3 5.0 X = 4.0 4.0 3.0MM LCL = 2.7 ul ulwulwwE 5 10 15 20 Subgroup number Subgroup mean шit UCL = 5.3 %3D 5.0 X = 4.0 3.0 LCL = 2.7 5 10 15 20 Subgroup number Subgroup mean