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The variance of first 20 natural numbers is

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Important Questions on Statistics

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In an examination, 20% of the students scored 70 marks, 40% scored 80 marks, 30% scored 90 marks and the rest scored 100 marks. Then the mean score of the students is
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The average marks of 30 students in a class was 80. After two students left out of the class, the average marks of the remaining students was 82. Then the average marks of the two left out students is
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The average weight of a class of 14 students is 42 kg. On including the teacher the average increases by 400 g, then weight of teacher is
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The mean of the values of 1,2,3,..n with respectively frequencies x, 2x, 3x, nx is
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If a variable takes the discrete values α+4, α-72, α-52, α-3, α-2, α+12,  α-12, α+5α>0, then the median is
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If the mean of a set of observations x1, x2, x10 is 20 , then the mean of x1+4, x2+8, x3+12, x10+40 is
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The arithmetic mean of C0n, C1, C2nn, Cnn is
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The sum of 10 items is 12 and the sum of their squares is 18, then standard deviation will be