Since all percentages are a fraction of some larger base, sometimes it’s helpful to re-define that base to make sense of a percentage — this is called rebasing. For example, if you ask a question to a smaller group of people and want to know how many of them said “yes,” you can either look at them as a percentage of only the people who responded to that question, or you can look at them as a percentage of everyone in the study. Changing the base that the percentage is using is called “rebasing.”