Set A, Set B, and Set C each contain only positive integers. : GMAT Data Sufficiency (DS)
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# Set A, Set B, and Set C each contain only positive integers.

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Set A, Set B, and Set C each contain only positive integers. [#permalink]

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20 Dec 2006, 18:38
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Set A, Set B, and Set C each contain only positive integers. If Set A is composed entirely of all the members of Set B plus all the members of Set C, is the median of Set B greater than the median of Set A?

(1) The mean of Set A is greater than the median of Set B.
(2) The median of Set A is greater than the median of Set C.
[Reveal] Spoiler: OA
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20 Dec 2006, 19:10
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given: A = B + C

(1) meanA > medB
------------------------
useless, the mean indicates nothing for finding medians
the mean can be easily misleading if one element is too large or too small

statement 1 is insufficient

(2) medA > medC
----------------------
although this could be a trap to make you think that the large medB cause medA > medC , the question says nothing about the number of elements in sets B and C. So, C could have like 10 elements while be has only 3 elements and thus the median of A could be larger than the median of B
on the other hand, B could have way more elements than C and thus resulting in a median of A smaller than the median of B

statement 2 is insufficient

(1) and (2) together
-----------------------
is still not helpful as the mean in A leads to nothing

OA ?
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20 Dec 2006, 21:48
Agree with E here. The mean and median are not related in any way that you can devise from the information given, and S1 and S2 provide only comparisons between their supposed relation.
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03 Dec 2009, 12:53
I got E as well. The mean tells us nothing about the median unless there is another specification (eg. consecutive numbers,etc.)
The median could be any number since the question stem does not specify how many numbers are in the set.
for example [1,2,3,4,100,1000], the mean can specify a very large number while the median would be 3.5.
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04 Dec 2009, 15:01
There are 2 imp points here Mean and Median are not related and another is the elements in any of the sets are not fixed so its just impossible to arrive at the answer.
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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12 Oct 2013, 16:11
mm007 wrote:
Set A, Set B, and Set C each contain only positive integers. If Set A is composed entirely of all the members of Set B plus all the members of Set C, is the median of Set B greater than the median of Set A?

(1) The mean of Set A is greater than the median of Set B.

(2) The median of Set A is greater than the median of Set C.

Hi experts, this question is indeed very interesting. Could you please share some of your knowledge on properties for statistics in combined sets.
I think I remember that for example the median of a combined set has to be between the median of of the subsets combined.
But are there any other properties that might be helpful to remember?

Please let us know, or anyone.
Will be happy to throw some kudos out there
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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15 Oct 2013, 20:17
This is a tricky question and statistics is my weakest area so far.
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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16 Oct 2013, 00:20
honchos wrote:
This is a tricky question and statistics is my weakest area so far.

Probably easiest way to solve would be to construct different sets. Try it.
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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17 Oct 2013, 21:27
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If Med(A) > Med(B), it tells me that the quantities in A are typically greater than B
For example Med(5,6,7,8,9) > Med(1,2,3,4,5,6,7,8,9)

Question to answer: is the median of Set B greater than the median of Set A?

(1) The mean of Set A is greater than the median of Set B.
This doesn't tell me much.
For example Mean(5,6,1000) > Med (7,8,9)

(2) The median of Set A is greater than the median of Set C.
Now this is something.
Lets take two lists.
Med(B)=Med(7,8,9,10,11) =9
Med (C) = Med(1,2,3,4,5,6,7) = 4
Now if we combine the two into set A, we should expect Med(C)<Med(A)<Med(B)
In our example, 6

Now lets change the balance between B and C
Med (B) = Med(7,8,9,10,11) =9
Med(C) = Med(12,13,14,15,16) = 14
Med (A) = Med(B,C) = 11.5
In other words, Med(B)<Med(A)<Med(C)

If we are told that Med(C) < Med(A), then Med(A) must be less than Med(B)
Sufficient.

I choose, B
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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18 Oct 2013, 04:27
portland wrote:
If Med(A) > Med(B), it tells me that the quantities in A are typically greater than B
For example Med(5,6,7,8,9) > Med(1,2,3,4,5,6,7,8,9)

Question to answer: is the median of Set B greater than the median of Set A?

(1) The mean of Set A is greater than the median of Set B.
This doesn't tell me much.
For example Mean(5,6,1000) > Med (7,8,9)

(2) The median of Set A is greater than the median of Set C.
Now this is something.
Lets take two lists.
Med(B)=Med(7,8,9,10,11) =9
Med (C) = Med(1,2,3,4,5,6,7) = 4
Now if we combine the two into set A, we should expect Med(C)<Med(A)<Med(B)
In our example, 6

Now lets change the balance between B and C
Med (B) = Med(7,8,9,10,11) =9
Med(C) = Med(12,13,14,15,16) = 14
Med (A) = Med(B,C) = 11.5
In other words, Med(B)<Med(A)<Med(C)

If we are told that Med(C) < Med(A), then Med(A) must be less than Med(B)
Sufficient.

I choose, B

Notice that the correct answer is E, not B.
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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18 Oct 2013, 12:32
Bunuel wrote:
Notice that the correct answer is E, not B.

Ah! did not notice that. Thanks.
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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19 Oct 2013, 04:07
portland wrote:
If Med(A) > Med(B), it tells me that the quantities in A are typically greater than B
For example Med(5,6,7,8,9) > Med(1,2,3,4,5,6,7,8,9)

Question to answer: is the median of Set B greater than the median of Set A?

(1) The mean of Set A is greater than the median of Set B.
This doesn't tell me much.
For example Mean(5,6,1000) > Med (7,8,9)

(2) The median of Set A is greater than the median of Set C.
Now this is something.
Lets take two lists.
Med(B)=Med(7,8,9,10,11) =9
Med (C) = Med(1,2,3,4,5,6,7) = 4
Now if we combine the two into set A, we should expect Med(C)<Med(A)<Med(B)
In our example, 6

Now lets change the balance between B and C
Med (B) = Med(7,8,9,10,11) =9
Med(C) = Med(12,13,14,15,16) = 14
Med (A) = Med(B,C) = 11.5

In other words, Med(B)<Med(A)<Med(C)

If we are told that Med(C) < Med(A), then Med(A) must be less than Med(B)
Sufficient.

I choose, B

I think the condition you mentioned that I have highlighted above doesn't satisfy the condition Median A > Median C

Consider these scenarios,

1) Set B = {3,3,3,3,3} Median of B = 3
Set C = {1,2,3} Median of C = 2
Set A = {1,2,3,3,3,3,3,3} Median of Set A = 3

Satisfies condition specified in Statement 2 i.e. Median of Set A > Median of Set C

But Median of Set B = Median of Set A

2) Set B = {3,4,5,6,7} Median of B = 5
Set C = {1,2,3} Median of C = 2
Set A = {1,2,3,3,4,5,6,7} Median of Set A = 3.5

Satisfies condition specified in Statement 2 i.e. Median of Set A > Median of Set C

But Median of Set B > Median of Set A

Consider Kudos if the post helps!!!
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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16 Apr 2014, 05:06
I would prefer algebra here..
Take two sets..
X1, X2, X3 - B
Y1, Y2, Y3 -C

With the possibility for Set C integers being the greater ones or Set B..There are other but..considering these 2 and the equations formed..It is enough to select an E with a cent percent surity
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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07 Sep 2015, 01:23
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Re: Set A, Set B, and Set C each contain only positive integers. [#permalink]

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28 Sep 2016, 03:27
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Re: Set A, Set B, and Set C each contain only positive integers.   [#permalink] 28 Sep 2016, 03:27
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