Sum of the frequencies up to the value of an observation or class is called cumulative frequency (cf) and its distribution is called cumulative frequency distribution.

Two types of cumulative frequency distribution are :

1. ‘Less than’ type cumulative frequency distribution: The sum of the frequencies upto the specified value of the observation or specified upper boundary point of a class is called ‘less than’ type cumulative frequency of that specified value or class and the distribution is called ‘less than’ type cumulative frequency distribution. Here, cumulative frequencies are in ascending order.

2. ‘More than’ type cumulative frequency distribution: The sum of all the frequencies of the specified value of the observation or the lower boundary point of the specified class and the values or classes succeeding to it, is called ‘more than’ type cumulative frequency and its distribution is called ‘more than’ type cumulative frequency distribution. Here, cumulative frequencies are in descending order.