Introduction to Equal Variance Assumption

Cookbook for Checking the Equal Variance Assumption

Minitab uses a homogeneity of variance test for assessing equal variances.
To check equal variances for two or more samples of data
1. Go to the Stat menu, select ANOVA.
2. Select Test for Equal Variances
3. In the Response box, enter the column containing the Y data.
4. In the Factors box, enter the factor or factors. For a two-sample t-test, the factor is simply an indicator variable which states which sample the each Y value belongs in. For ANOVA, there are 2 or more factors.
5. Click Okay.
6. You will see a display as shown below. Check the p-value associated with the Bartlett’s test, Levene’s test, or F test. Also check the confidence intervals for the standard deviations.