Remove Point from Control Chart Calculations (Ghost Point)

Jay Arthur
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KnowWare International, Inc.
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While it is not usually recommended, many customers have asked for the ability to leave a point on a control chart BUT remove the point from the control limit calculations. Using the chart pull down menu, the QI Macros now give you this capability.

To remove a point from the calculations but leave it on a chart:

1. Click on the point to be removed. Note: The first time you click on the point, Excel will select the whole line. Click on the point a second time to get just the point. If you have done this correctly, Excel will highlight your point and the point before it.



2. Select the QI Macros Chart menu and select Ghost Point.



3. The point marker will change to designate that the point has been "ghosted."



4. Next re-run stability analysis with the new control limits.
5. If you want to check the control limit calculations, go to the data sheet where the formulas are created and click on one of the average cells. Look in the formula box to view the formula. You will notice that the row that the ghosted point is in has been removed from the calculations. In the example below, the point in row 19 has been removed.



6. You may also want to add text to the point to further highlight that it has been removed from the calculations.

Excel 2007 Workaround for Ghosting a Point on an Imbedded Chart

QI Macros Control Chart Menu Features

• Add Data to Control Charts
• Remove (Ghost) Point from Control Chart Calculations
• Delete Point from Control Chart
• Add Text to Data Point
• Show Process Change on Control Chart
• Analyze Stability with Control Chart Rules

Add Target or Goal Line to Chart

Other QI Macros and Control Chart Articles

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