JEE Main Questions
For a group of 200 candidates the mean and S.D. were found to be 40 and 15 respectively. Later on it was found that the score 43 was misread as 34. Find the correct mean and correct S.D.
Solution: Solution: Incorrect mean is . There are candidates.
This is incorrect as was misread as .
Now, we will find the correct standard deviation.
When incorrect observations was present, then standard deviation was .
This is the sum when observations were incorrect.
So, the correct standard deviation is .