A set of data consists of the following 5 numbers: 0,2,4,6 and 8.Which two numbers,if added to create a set of 7 numbers will result in a new standard deviation that is close to the standard deviation for the original 5 numbers?
A.-1 and 9
B. 4 and 4
C. 3 and 5
D. 2 and 6
E. 0 and 8
OA is D
I have already posted this question sometime back in this forum..But I still have my doubts on whether this problem can be solved using a shorter method without the application of formulas....I kindly request the experts to suggest the best approach to tackle this problem..
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Standard Deviation
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raju232007
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rohangupta83
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I could do it only by calculating standard deviation individually
That way it's too long - if there is a better way, please let me know
That way it's too long - if there is a better way, please let me know
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schumi_gmat
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SD of 5 numbers is sqrt(40/7) = sqrt(8)
only way we can get 8 again is by adding 0 and 8, i.e 40+16)/7 = 8
hence IMO E
only way we can get 8 again is by adding 0 and 8, i.e 40+16)/7 = 8
hence IMO E
Actually all the numbers adds to 8schumi_gmat wrote:SD of 5 numbers is sqrt(40/7) = sqrt(8)
only way we can get 8 again is by adding 0 and 8, i.e 40+16)/7 = 8
hence IMO E
we are waiting for Ian or some other expert to comment on.
