Each of the eight tests for special causes detects a specific pattern in the data and such occurrence indicates a special cause for the variation. You can change the test parameter to adjust test sensitivity.
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One point is more than 3s from center line. | |
Two out of three consecutive points more than 2s from center line (same side) |
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Nine consecutive points Nine on same side of center line | |
Four out of five consecutive points more than 1s from center line (same side) |
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Six consecutive points, all increasing or all decreasing | |
Fifteen consecutive points within 1s of center line (either side) |
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Fourteen consecutive points, alternating up and down | |
Eight consecutive points more than 1s from center line (either side) |
At the Excel Menu (For Excel 2007, go to Add-ins first)
Choose ProcessMA > Control Charts > Define Tests
Enter k values for the respective tests (integer, between allowable range)
Click OK to save changes
Click Default to reset k values to original setting
Click Cancel to close dialog box without saving
The figure below shows a screenshot of the dialog box to adjist the sensitivity of the control charts
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