Frequency is how many times something happens at a given point. The cumulative frequency is the number of times something happens at multiple given points. For example, if a teacher grades a test, and five students get in between 71 and 80, five is the frequency. If on the same test, six students score between a 81 and 90, the cumulative frequency from 71 to 90 is 11. This is an important basic statistic to help in more complex statistical calculations, such as mean.
Write out your data, separating the data into data sets. For example, a day care centre has 11 students ages 1 to 5; 14 students ages 6 to 10; and seven students ages 11 to 15. Written out in a table form:
Ages / Frequency
1-5 / 11
6-10 / 14
11-15 / 7
Add the frequency of the first data set to the second data set. In the example, 11 plus 14 equals a cumulative frequency of 25 for ages 1 to 10.
Repeat adding together the next frequency until you add together all the frequencies of your data sets. In the example, the frequency for ages 1 to 15 would be 32.