Question

The mean of 100 observations was calculated as 40. it was found later on that one of the observations was misread as 83 instead of 53. the correct mean is

Answer 1

Mean marks of 100 students = 40
Sum of marks = 100 × 40 = 4000
Given that one observation is misread as 53 instead of 83
Hence, error in reading the marks = 83 – 53 = 30
Correct sum of observations = 4000 – 30 = 3970
Therefore, correct mean = 3970/100 = 39.7