One of the most powerful features of Crystal is the ability to Group data. When you get right down to it, all analysis by definition is based upon Groupings. Dollars per hour. Calls per day.
And once you have some summaries working for you, groups, then, become synonymous with Dimensions. Think pivot tables.
It is a very common thing to change the dimensions of a report.
In Crystal, select Report | Change Group Expert.
From here, you can select a Group and use the arrow [mouse] buttons to change the "level" of the Group.
Clicking "Options" will allow you to change the Group Field, effectively picking a different dimension.
Pro Tip : I often recommend that a formula be used as a Group field, instead of the "raw" database field. The reason being is that you retain control over what's in the Group based upon the formula, and not necessarily the Group Expert.