The mean and standard deviation of 20 observations are found to be 10 and 2, respectively. On rechecking, it was found that an observation 8 was incorrect.
Calculate the correct mean and standard deviation in each of the following cases:
If it is replaced by 12
It is given in the question that,
Total number of incorrect sum of observations = 200
Also, correct sum of observations = 200 – 8 + 12
= 204
= 10.2
Now, we know that:
Thus, 
= 2080 – 64 + 144
= 2160
= 1.98
5