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: B
The incorrect sum of observations = 100 × 40 = 4000.
The difference due to misreading = Incorrect value - Correct value = 83 - 53 = 30.
The calculated sum is 30 more than the actual sum.
Correct sum = 4000 - 30 = 3970.
Correct mean = \(\frac{3970}{100} = 39.7\).