Question

The mean of the following frequency distribution is 62.8 and the sum of all the frequencies is 50. Compute the missing frequency f₁ and f₂.

Class:	0−20	20−40	40−60	60−80	80−100	100−120
Frequency:	5	f1	10	f2	7	9

Answer 1

It is given that mean = 62.8 and .

Let the assumed mean A = 50 and h = 20.

.....(1)

We know that mean,

Now, we have , , .

Putting the values in the above formula, we have

.....(2)

Putting the value of in (2), we get

Putting the value of in (1), we get

Hence, the missing frequency f₁ = 8 and f₂ = 12.