To display an interval plot with groups
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1    Choose Stat > ANOVA > Interval Plot or Graph > Interval Plot.

2    Under One Y, choose With Groups. Click OK.

3    In Graph variables, enter one or more columns of data. Minitab displays a separate graph for each column.  

4    In Categorical variables for grouping (1-4, outermost first), enter one to four columns of grouping (categorical) variables. The first variable is the outermost on the scale and the last variable is the innermost.

5    If you like, use any dialog box options, then click OK.