Question

Find the mean of each of the following frequency distributions :

Class interval:	10−30	30−50	50−70	70−90	90−110	110−130
Frequency:	5	8	12	20	3	2

Answer 1

Let the assumed mean be A = 60 and h = 20.

We know that mean,

Now, we have.

Putting the values in the above formula, we have

Hence, the mean is 65.6.