Deviation Taken from Assumed Mean

This methods  is assorted  when the  arithmetic  average  is a  fractional value. Taking  deviation from  fractional value would  be a very  difficult and tedious task. To save time  and labor we apply  short  cut methods deviations are taken  from  and assumed mean. The followings are the  steps.

a.Assume any  one  of the item  in the series as an average(A).

b.Find out  the deviation from  the assumed mean i e, X-A denoted by d.

c.Find out  the total  of the deviation  i ,e, ∑d.

d.Square the deviations i ,e, d² and add up  the squares of devotion i ,e, ∑d².

e.Then  substitute the  values  in the  followings  formula.

        = √ ∑d²- / N - ( ∑d²)/N 2

Where  d stands  for the  deviation from  assumed mean = ( X-A)

 Note : If the actual  mean in fraction then it is  better to take  deviations form  an assumed mean  for  avoiding  too much  calculation.