Graph > Boxplot > choose Multiple Y's - With Groups > OK
Use to display boxplots of multiple variables with groups on the same graph.
Graph Variables: Enter one or more columns of data. Minitab displays all columns on the same graph.
Categorical variables for grouping (1-3, outermost first): Enter one to three columns of grouping (categorical) variables. Minitab displays all groups on the same graph. (To panel by one or more variables, use By Variables.) The first variable is the outermost of the grouping variables on the scale.
Scale Level for Graph Variables
Graph variables displayed outermost on scale: Choose to make the graph variables the outermost groups.
Graph variables displayed innermost on scale: Choose to make the graph variables the innermost groups.