NCERT Class 11 Mathematics Solutions: Chapter 15 –Statics Miscellaneous Exercise Part 4
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Formula of Standard Deviation
1. The mean and standard deviation of observations are found to be and , respectively. On rechecking, it was found that an observation was incorrect. Calculate the correct mean and standard deviation in each of the following cases:
(i) If wrong item is omitted.
(ii) If it is replaced by .
Answer: (i)
Number of observations
Incorrect mean
Incorrect standard deviation
That is, incorrect sum of observations
Correct sum of observations
Correct Mean
Standard deviation
Answer: (ii)
When is replaced by ,
Incorrect sum of observations
Correct sum of observations
Correct Mean
Standard deviation