Cumulative frequency
- CBSE · NCERT Class 10, Ch 13 Statistics
The cumulative frequency of a class is its own frequency added to the frequencies of all the classes before it.
Cumulative means building up. Go down a frequency table and keep a running total. Each total tells you how many values lie up to the end of that class. The last running total always equals n, the total frequency. That is a quick check on your adding.
A small example
Four classes have frequencies 4, 7, 9 and 5. The cumulative frequencies are 4, then 4 + 7 = 11, then 11 + 9 = 20, then 20 + 5 = 25. The last one, 25, equals the sum of all four frequencies, so the column is right.
Where marks go
Question 10 of CBSE's 2026-27 Maths Basic sample paper gives five classes with a total frequency of 66. It asks for the lower limit of the median class. The 2026-27 Maths Basic marking scheme finds n/2 = 33 and places it in the class 10-15, so the answer is 10.
The running totals are 10, 25 and 37 by that class. It is a multiple-choice question. Section A carries no part marks, unlike the step marking in longer answers. A slip in the running total picks a wrong class and scores 0. In the median formula, cf is the total for the class just before the median class, not the median class itself.
Sources
Facts last checked against these sources on 30 September 2026.
About the author
Chief Architect
An engineer (B.Tech, Computer Science) with over 20 years of preparing students for entrance exams, including as Dean at FIITJEE and Vice-President at Aakash. He is the chief architect of the TRUpreBoards evaluation engine.
Mohit Sardana on LinkedIn
