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median

by ketkoag » Wed Jun 10, 2009 12:54 am
If 2 numbers are picked out from 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, what's the deviation of the remaining numbers?
1) The median of the remaining numbers is 10
2) The average value doesn't change

[spoiler]IMO : D, please confirm the answer..[/spoiler]
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Re: median

by iamcste » Wed Jun 10, 2009 1:24 am
ketkoag wrote:If 2 numbers are picked out from 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, what's the deviation of the remaining numbers?
1) The median of the remaining numbers is 10
2) The average value doesn't change

[spoiler]IMO : D, please confirm the answer..[/spoiler]
yes IMO D

d=constant difference=2, mean=median

1. this means 1 and 19 are out to get median 10.. for the remaining nos, we can find standard deviation as we know data set as well as the mean( =median)

2. Current average=10..even after removing 2 integers, average=10

Also as mean=median...this statement can be rephrased to statment "The median of the remaining numbers is 10"

Sufficient
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by ketkoag » Wed Jun 10, 2009 2:26 am
thanks
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by tohellandback » Wed Jun 10, 2009 6:20 am
I think the answer should be E

in both the cases we can remove any of the 5 pairs of numbers and it satisfies the condition but it will change the standard deviation.


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by mikeCoolBoy » Wed Jun 10, 2009 10:23 am
I agree with tohellandback

the mean for the initial set is 10 = (1+19)/2

1) says that the new mean is 10
you can remove the pairs (1,19), (3,17), (5,15) ... and the mean is 10 but the standard deviation changes

2) if you remove the any of the pairs I mentioned you get the same mean but the standard deviation changes.
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