Question

Mean of nine observations was found to be 35. Later on it was known that observation 81 was misread as 18. Find the correct mean of the observation

Answer 1

Mean of 9 observations = 35 (Given)

Sum of 9 observations = 35×9

Sum of 9 observations =315

since 81 was misread as 18

Then, sum of new observations =[315- (wrong observation)+(correct observation)]

= 315-18+81

= 315+63= 378

The correct mean = some of new observation/total number of observations

Correct mean= 378/9= 42

Hence, the correct mean is 42.

Hope this will help you....