JEE MATHEMATICS MCQ: STATISTICS

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The mean of 20 observations is 15 . On checking it was found that the two observations were wrongly copied as 3 and 6 . The correct values are 8 and 4 , then correct mean will be given by

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Correct option: A

15.15

Option A (15.15) is correct because the correct mean is calculated by subtracting the incorrect values and adding the correct values to the original sum, then dividing by the number of observations.

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If the mean of a set of observations

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\bar X,

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the s.d. of the new set of observations will be