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arjtryarjtry
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arjtryarjtry
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arjtryarjtry
i think it is E.
for same avg/ median, we ahve to remove nos symetrical about the median nos.
so if we remove 6 and 16, we get a diff SD than when we remove ,say 4 and 18.
is logic ok?
Sorry I messed up with idea, you are right.
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abhijit.. it happens ... GMAT was made to make fools out of us.... :lol:

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. If two numbers are removed from 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20, what is the standard deviation of the remaining numbers?
(1) The average remains unchanged after the numbers removing.
(2) The median remains unchanged after the numbers removing.

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I will go with D.

Since, the numbers are consecutive even numbers, average or median will remain the same only if the two extreme numbers are removed. And, hence, it will be possible to calculate the SD.
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I think E.

We have from the stem that the average is the same as the median and it is 11. We can remove two numbers without changing the median/average, by removing any of the pairs: 2&20, 4&18, 6&16, 8&14, 10&12. I never bothered to remember how stdev is calculated, but if we remove 2 and 20, it will be different than removing 10 and 12, right?
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If you remove 4 and 18 or 6 and 16, the average will change.
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Oops....my silly mistake.....it will be E.
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Even though average/median remains the same, the SD for a subset of the numbers will be different because the numerators (in calculation of SD) varies. Hence E
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arjtryarjtry
. If two numbers are removed from 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20, what is the standard deviation of the remaining numbers?
(1) The average remains unchanged after the numbers removing.
(2) The median remains unchanged after the numbers removing.
When we symmetrically remove the data the mean and median remain unchanged but SD is distance from the mean hence which values removed does matter here !!!Hence in both the options cant say!!
IMO E



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