Question

the mean of a hundred observations was found to be 40, later on it was discovered that a score of 27 was misread as 57 find the correct mean.

Answer 1

(57 + x)= 4000
x = 3943

(3943+27)/100 = 3970/100 =39.7

Answer 2

mean score = 40

mean=sum of observation /no of observations

  

sum of observations = mean x no of observations

 

that is 40 x 100

     

           = 4000

after replacement, sum of new observation=4000-83+53

                                                                    =4970

mean of new observation = 3970/100

                                         =39.7

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