When you create a graph with groups, by default, Minitab includes groups that have no names and groups that have no data. Use the following options to exclude these groups from your graph.
To exclude groups that have missing names when you create the graph, click Data Options. On the Group Options tab, deselect Include missing as a group.
To exclude empty cells when you create a graph, click Data Options. On the Group Options tab, deselect Include empty cells. To remove empty cells from an existing graph, double-click the scale and deselect Include empty cells on the Scale tab.