Aakash0101raj wrote:
Set A={9, 13, 4, 2, 7}
Set B={9, 13, 4, 2, 9}
Set C={9, 13, 4, 2, 4}
Set D={9, 13, 4, 2, 6}
Which of the following statement illustrates the exact order of standard deviation of these sets of numbers from the lowest to the greatest?
A. A < B < C < D
B. A < B < D < C
C. D < B < C < A
D. C < B < D < A
E. A < D < B < C
1. The common elements of all these sets are 2,4,9,13 whose average is = 28/4 =7
2. After that we check the absolute difference between the arithmatic mean (=7) and the numbers we are appending to the remaining sets i.e the last numbers in all the 5 sets.
3. The larger the difference, the larger the standard deviation.
That means, for Set A 7~7=0, Set B 9~7 =2 , Set C 4~7=3, Set D 6~7=1. (Normally we know if we append a value equal to the mean to the set, the standard deviation would decrease the most. So obviously A has the least standard deviation)
Therefore the answer would be, A<D<B<C
(E)