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# median mean and range correlation

Author Message
Manager
Joined: 25 Aug 2011
Posts: 198

Kudos [?]: 375 [0], given: 11

Location: India
GMAT 1: 730 Q49 V40
WE: Operations (Insurance)
median mean and range correlation [#permalink]

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02 Mar 2012, 23:44
Set S consists of positive numbers. If -1 is added as an element to set S, which of the following is impossible ?

The mean will decrease but median will not change.
The median will decrease but mean will not change.
The range will increase but median will not change.
The range will increase but mean will decrease.
The standard deviation will increase but mean will decrease.

what is the best way to test this.. Am getting bogged down by picking numbers .. Also on picking numbers am unable to decide between A B and C - all seem impossible. Pl help

Kudos [?]: 375 [0], given: 11

Math Expert
Joined: 02 Sep 2009
Posts: 41891

Kudos [?]: 128906 [0], given: 12183

Re: median mean and range correlation [#permalink]

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03 Mar 2012, 00:15
devinawilliam83 wrote:
Set S consists of positive numbers. If -1 is added as an element to set S, which of the following is impossible ?

The mean will decrease but median will not change.
The median will decrease but mean will not change.
The range will increase but median will not change.
The range will increase but mean will decrease.
The standard deviation will increase but mean will decrease.

what is the best way to test this.. Am getting bogged down by picking numbers .. Also on picking numbers am unable to decide between A B and C - all seem impossible. Pl help

The mean of set S is sum/n, where n is # of terms in set S.

Since set S consist of positive numbers, then when we add -1 to the set the sum of the numbers in the new set will decrease. So, the new mean will be (less sum)/(more terms)=(less sum)/(n+1), which will be less than the sum/n. Hence the mean must decrease.

P.S. If it's GMAT Club question please site # of test and # of question.
_________________

Kudos [?]: 128906 [0], given: 12183

Re: median mean and range correlation   [#permalink] 03 Mar 2012, 00:15
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# median mean and range correlation

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