UN-GROUPED FREQUENCY DISTRIBUTION -
ii) ASSUMED MEAN METHOD-
When the product fᵢyᵢ involves large numbers, we use the assumed mean method for finding the mean and proceed step wise as under.
Step.1) We have to choose a suitable value of yᵢ in the middle as the assumed mean and call it A.
Step.2) Now, we should calculate the deviation dᵢ = (yᵢ - A) for each yᵢ
Step.3) Now, we have to calculate the product fᵢdᵢ for each i
Step.4) Now, we have to find the value of Ʃ fᵢdᵢ and Ʃ fᵢ
Step.5) Now, we have to calculate the mean using the formula –
Mean = A + -----------
Example) Using the assumed mean method, find the mean weekly wages from the data given below –
Ans.) Let the assumed mean A = 140
Now, we can arrange the given data as under.
Mean, y = A + -------------
= 140 + ----------
= 140 + 2.54
Hence mean weekly wages = $ 142.54 (Ans.)