Math CentralQuandaries & Queries


Question from Jim, a student:

When using a scale e.g. 0-10, what is the formula for calculating percentage change. For example when someone answers a questionnaire where a question has a 0-10 scale, and they score a 4 first time, and then they answer the same questionnaire a different day, and they score an 8, how do I calculate the percentage change.

would it be (100/total number of points on the scale, in this case 11[including 0]) x points changed on the scale [in this case 4]?

Thanks in advance for your time

Hi Jim,

The initial score was 4 points and the second score was 8 points so the change was $8 - 4 = 4$ points. Percentage change is the change, as a percentage of the initial value. Thus the percentage change in this case is

\[\frac44 \times 100 = 100\%.\]


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