Using the Variation Wizard

The GainSeeker Variation Wizard helps you find the sources of variation in SPC data so you can work to improve your processes. The Variation Wizard is accessible from SPC Control charts*.

 

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*GainSeeker Charts module control chart types from which you can open the Variation Wizard include: Control, Combination, X-Bar/Moving range/Range, Scatter, and Cusum/Control charts.

Opening the Variation Wizard

There are three ways to open the Variation Wizard from a control chart.

The Variation Wizard opens.

Tip: You can press the F1 key any time you are using the Variation Wizard to open this help topic for quick reference.

Step 1 of the Variation Wizard

The Control chart in this example exhibits out of control points. Data points that originate from special causes should be excluded from the analysis before proceeding with the wizard analysis.

If you are unfamiliar with the system that is producing this data, you may want to study the Control chart from which you launched the Variation Wizard. You may also want to become familiar with the traceability relationships for this system so that you can make informed decisions from the Variation Wizard results.

Checking for out of control points before performing the analysis

You can also check for points out of control in the data on Step 1 of the wizard, by checking the message area diagrammed below and you can click the Stability Info button to display information about the current chart.

Information about the current chart used in this example displays when the Stability Info is clicked:

This example shows how it will display after all points are excluded:

Next, select the traceability values used in the analysis

Select whether each selected traceability is Discrete or Continuous

Select the minimum number of items to include as a group in the analysis

Determine how traceability data is ranked

 

Step 2 of the Variation Wizard

This step displays the variation analysis of all the traceability values you selected in Step 1 for which at least two distinct data groups were found. In this example, data grouped by Operator and data grouped by Shift (both ranked 1) share the most Significant difference in variation in spread for the discrete traceability.

You can draw a new chart to display the variation between groups. The results in the column labeled Rank list from top to bottom in order of variation in spread and a central tendency for discrete traceability or correlation for continuous traceability.

Next, select one or more values in the list and then click the Chart button to create new charts that are grouped according to traceability. For continuous traceability, you can click the Scatter plot button to help analyze your data.

When Shift is selected for further analysis by clicking the Chart button on the wizard, the following chart generates.

See Traceability labels and lists

If you have discrete traceability, you will have a list like the one on top where the traceability is ranked and the significance of variation between groups is based on the F-Test and t-Test1 results. The F-Test checks to see if the spread of two groups are significantly different, and the t-Test checks if the means of two groups are significantly different. You should start with the highest-ranked item in the list and look at the chart by the selected traceability. You may quickly decide that although the variation is significant, the differences between groups are not large enough to make any changes.

To exclude out of control chart signals from the analysis:

  1. Close the Variation Wizard, and then right-click the chart from which the wizard was opened.
  2. Click Settings on the right-click menu that displays.
  3. On the Settings tab that opens, enter text in the Search field, such as exclude to display the Data outside Control limits excluded setting. (For more help with using search criteria, see Searching for settings on the Settings tab). Click the Data outside Control limits excluded setting to select it.