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Which of the following is impossible

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Which of the following is impossible

by rahulvsd » Fri Apr 20, 2012 6:25 am
Set S consists of positive numbers. If -1 is added as an element to set S, which of the following is impossible ?

A) The mean will decrease but median will not change.
B) The median will decrease but mean will not change.
C) The range will increase but median will not change.
D) The range will increase but mean will decrease.
E) The standard deviation will increase but mean will decrease.

[spoiler]OA: B[/spoiler]
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by Brent@GMATPrepNow » Fri Apr 20, 2012 7:11 am
rahulvsd wrote:Set S consists of positive numbers. If -1 is added as an element to set S, which of the following is impossible ?

A) The mean will decrease but median will not change.
B) The median will decrease but mean will not change.
C) The range will increase but median will not change.
D) The range will increase but mean will decrease.
E) The standard deviation will increase but mean will decrease.

[spoiler]OA: B[/spoiler]
If set S consists of positive numbers, then the sum of those numbers will be positive.
If we add -1 to set S, the sum will decrease.
As such, the mean must decrease as well.
Since B suggests that the mean will not change. B is the correct answer.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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