Building a Cumulative Frequency Table

A cumulative frequency distribution shows how data build up across class intervals. Instead of counting only the values in one class, it counts the values in that class and in every class to its left. It is a useful way to track how data accumulate as the table progresses.

A cumulative frequency ...

Consider a frequency distribution of customers who bought cameras at different price ranges. The table shows that three customers bought cameras that cost from 40 to 59 dollars.

To find out how many customers bought cameras that cost less than 60 dollars, calculate the cumulative frequency for the first two classes. It is given by the sum...