Use the test for equal variances to determine whether the variances or the standard deviations of two or more groups differ.

For example, a lumber distributor wants to compare the variation of a cutting process before and after a process improvement. To see an example, go to Minitab Help: Example of Test for Equal Variances.

To add output from an equal variances test, go to Add and complete a form.

Data considerations

You must have at least one categorical factor (X) and a continuous response (Y). To use an equal variances test, you must collect a sample at each level of the input. The sample sizes should be greater than 20. If some of the groups have fewer than 20 samples, the multiple comparisons p-value might not be valid. For details, go to Minitab Help: Data considerations for Test for Equal Variances.

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