Question

Mean of 36 observations is 12. One observation 47 was misread as 74. Find the correct mean,

Answer 1

Mean = Sum of observations / No. of observations 

Mean of 36 observations = 12
Sum of 36 observations = 12 × 36 = 432

Actual sum
= Sum of 36 observations - incorrect observation + correct observation
= 432 - 74 + 47
= 405

∴ Correct mean = Actual sum of 36 observations/36 = 405/36 = 11.25