JEE MATHEMATICS MCQ: STATISTICS

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A sample of 35 observations has the mean as 30 and SD as 4. A second sample of 65 observations from the same population has mean as 70 and SD as 3. The SD of the combined sample is

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Correct option: D

None of these

Option D (None of these) is correct because the calculated standard deviation of the combined sample is approximately 19.38, which is not among the given options.

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If the mean of a set of observations

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\bar X,

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is The sum of 10 items is 12 and sum of their squares is 18 , then standard deviation will be In a family, there are 8 men, 7 women and 5 children whose mean ages separately are respectively 24,20 and 6 years. The mean age of the family is The mean and variance of seven observations are 8 and 16, respectively. If 5 of the observations are 2, 4, 10, 12, 14, then the product of the remaining two observations is

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