Question

What is the cumulative frequency of the modal class of the following distribution?

Class	3−6	6−9	9−12	12−15	15−18	18−21	21−24
Frequency	7	13	10	23	4	21	16

Answer 1

​Here the maximum class frequency is 23, and the class corresponding to this frequency is 12−15.

So, the modal class is 12−15.

Now, to find the cumulative frequency let us put the data in the table given below:

Class	Frequency (fi)	Cumulative frequency (cf)
3−6	7	7
6−9	13	20
9−12	10	30
12−15	23	53
15−18	4	57
18−21	21	78
21−24	16	94
Total	N = ∑fi = 94

Thus, the cumulative frequency of the modal class is 53.