Visualizer User Guide  7.5.0
Statistical Charts >

Use a Control Limits Chart

Control limits charts show whether the variance in your data is within tolerance levels that you set in the chart. The control limits chart is actually two charts. The top chart plots the data values for a numeric data item across an ordered text item, such as Product Type. The bottom chart shows the size of the variance between data points by plotting the moving range. The moving range is the difference between a data point and its predecessor on the horizontal axis in the top chart.

The control limits chart does not calculate statistics to draw the chart, but uses waterlines based on the following statistics:

  • mean

  • standard deviation

The sample chart named Control Limits is an example of a control limits chart.

Steps to insert the Control Limits Chart

  1. From the Insert menu, click Chart.

  2. Click Manually insert a chart.

  3. Ensure that the Insert into selected panel check box is cleared.

  4. Click 2D panel, select the Control Limits chart, and click Next.

  5. Do one of the following:

    • If another chart already exists in the visualization, click Add, and select Quantity_Sold_by_Month2006.txt from the list of data sources, and then click the right arrow icon  to add it to the Selected box.

    • If the visualization is blank, select Quantity_Sold_by_Month2006.txt in the list of data sources and click the Insert Data Source icon to add it to the Selected box.

    The Text Settings dialog box appears.

  6. In the Format box, select Tab delimited, and click OK.

    The file appears in the Selected list.

  7. Click Next.

  8. In the Data Item Properties dialog box, choose the following settings.

    Items box

    Item Type box

    OrderMonth

    Text

    SumOfQuantity

    Number

  9. Click Next.

  10. In the Set Chart Settings dialog box, in the Data source box, select Quantity_Sold_by_Month2006.txt.

  11. In the Settings box, select Sequence Axis (X), and then in the Data item box, select OrderMonth.

  12. In the Settings box, select Value Axis (Y), then in the Data item box, select SumOfQuantity.

  13. Click Finish.

Steps to Format the Top Chart

  1. In the top chart, click the vertical axis.

  2. If the property sheet is not open, from the View menu, click Properties.

  3. Under Numeric Precision, in the Intervals box, type 5, and press Enter.

  4. In the Decimal places box, type 0, and press Enter.

  5. In the Waterlines box, select the Mean check box.

  6. In the Alignment box, select Inside Left.

  7. Click an element in the chart.

    The chart property sheet opens.

  8. In the Title box, type Quantity, and press Enter.

  9. Under Marker, in the Weight box, type 4, and press Enter.

  10. Click Use a single color, and then in the color well, select black.

The top chart should now match the top chart of the sample named Control Limits provided in the visualization named Sales_Territory.viz.

Steps to Format the Bottom Chart

  1. In the bottom chart, click the vertical axis.

  2. Under Numeric Precision, in the Intervals box, type 5, and press Enter.

  3. In the Decimal places box, type 0, and press Enter.

  4. In the Waterlines box, click Add.

  5. In the Add Waterline dialog box, click Statistical Waterline.

  6. In the Chart box, select the chart to which you are adding the new waterline.

  7. In the Statistical computation box

    • For the standard formula, select Mean + n standard deviations and in the n box, type a value for n, and click OK.

    • For the alternate formula, select Mean + 'n' * average moving range and in the n box, type a value for n. The default value is 2.66. For more information, see Alternate Formula.

  8. In the Label box, type a label for the waterline or accept the default label, and click OK.

  9. In the Alignment box, select Inside Left.

  10. Click an element in the bottom chart.

    The chart property sheet for the bottom chart opens.

  11. In the Marker box, choose the line marker settings:

    • In the Weight box, type 4, and press Enter.

    • Click Use a single color, and then in the color well, select black.

  12. Click the horizontal axis, and then in the property sheet, click the Format tab.

  13. In the Axis Tick Label box, choose axis tick label settings:

    • Clear the Autofit check box.

    • Click the font button . Change Size to 7, and click OK.

    • In the Rotation box, type 30, and press Enter.

The bottom chart should now match the top chart of the sample named Control Limits provided in the visualization named Sales_Territory.viz.


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