
166 Six Sigma Case Studies with Minitab
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to the dialog box shown in Figure10.6. Click on “OK”, and the multivariate
chart shown in Figure10.8 is plotted. (Please note that the chart is shown in
grayscale here, although it has colored dots.) Each black dot is the average
waiting time for a combination of location and service type. Each red dot is
the average waiting time for each level of location. The following interpreta-
tions can be made from Figure10.8:
• The average waiting time at Location 1 (Copley) is longer than that
at Location 2 (Kenmore).
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35
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10
1
2
3
Service
Type
Factor 1 is Service Type, and Factor 2 is Lo ...