NCERT Class 11 Mathematics Solutions: Chapter 15 –Statics Miscellaneous Exercise Part 4

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In figure formula of standerd Deviation is shown.

Formula of Standard Deviation

In figure formula of standerd Deviation is shown.

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