In the Variability Chart platform, the Heterogeneity of Variance Tests option performs a test for comparing variances across groups. The test is an Analysis of Means for Variances (ANOMV) based method. This method indicates whether any of the group standard deviations are different from the square root of the average group variance. For an example, see Example of the Heterogeneity of Variance Test.
To be robust against non-normal data, the method uses a permutation simulation to compute decision limits. For more information about this method, see Wludyka and Sa (2004). Because the method uses simulations, the decision limits can be slightly different each time. To obtain the same results each time, assign a random seed in the launch window.
The red triangle menus for the test reports contain the following options:
Set Alpha Level
Sets the alpha level for the test.
Show Summary Report
Shows or hides a summary report for the test. The values in the report are the same values that are shown in the plot.
Display Options
Enables you to show or hide the decision limits, decision limit shading, and center line. There are also points options that you can use to show needles, show connected points, or show only points.