Cumulative Frequency of a Class Interval

The sum of the frequencies of all the previous classes and that particular class, is called or considered as the Cumulative Frequency of the class.

Cumulative Frequency Table –

A table which shows the cumulative frequencies over various classes is called a cumulative frequency distribution table.

Example.1) Following are the ages (in years) of 360 patients, getting medical treatment in a hospital.

Construct the cumulative frequency table for the above data.

Ans.) The cumulative frequency table for the above data is given below.

This table may be presented in “Less than Form”, as under.

Example.2) The monthly wages (in rupees) of 28 labours working in a factory are given below –

220, 268, 258, 242, 210, 267, 272, 242, 311, 290, 300, 320, 319, 304,302, 292, 254, 278, 318, 306, 210, 240, 280, 316, 306, 215, 256, 328. Form a cumulative frequency table with class intervals of length 20

Ans.) We may form the table as under –