Question

Find the mean using step division method
class:0-10 10-20 20-30 30-40 40-50 50-60
frequency 12 18 27 20 17 6​

Answer 1

∴ Mean = A + (Σft/Σf) × i

Mean = 35 + (-43/100) × 10

Mean = 35 + (-43/10)

Mean = 35 - 4.3

Mean = 30.7

Here,

A → Assumed mean

i → Upper limit - Lower limit

x → Mid-value

f → Frequency

Any number can be taken as assumed mean. But to make the calculations simpler, the assumed mean should be taken from the middle of the values of x.

The mean has been calculated by using the step-deviation method. There are other two methods too. Short-Cut method and Direct method. Whichever method of finding the mean is used, the mean in each case, will be the same.