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Re: If sets X and Y have an equal number of elements, does set X have a [#permalink]
That said, i agree with IanStewart completely. I had to make a lot of assumptions to arrive at this answer. Should not be the case with the actual test. This question is very ambigous and can be answered in many ways with different Options.
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Re: If sets X and Y have an equal number of elements, does set X have a [#permalink]
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I agree with you all. Ivy is the name of the book that I am following and some questions are really vague. My apologies.
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Re: If sets X and Y have an equal number of elements, does set X have a [#permalink]
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If sets X and Y have an equal number of elements, does set X have a greater standard deviation than set Y?

(1) The difference between each pair of the neighboring elements is consistent throughout each set;
(2) Each of the first two elements in Set Y is twice greater than the corresponding first and second elements in Set X.

Solution

Solution:

1) We are told that both sets are arithmetic progressions. Although both sets X and Y have the same number of elements, a very important fact, the statement neither specifies the distributions of the arithmetic sequence for each of the sets NOR a relationship between how the arthimetic progression between the two sets relate. Either would have done. Ex.

X={2,4,6,8,10} A.P. with spacing of 2
Y={5,10,15,20,25} A.P with spacing of 5.

In this case Y has a higher standard deviation(large spacing) than X. The reverse could be flipped:

X={6,12,18,24,30} A.P. with spacing of 6
Y={5,10,15,20,25} A.P with spacing of 5.

In this case X has a higher standard deviation(large spacing) than Y.

2) Doesn't tell us how the numbers after the first two terms play out. Ex:

X={3,7,10000}
Y={6,14,20}

X has the larger SD in this example.

X={3,7,5}
Y={6,14,2000}

Y has the larger SD in this example.

Hence INSUFF

(1) & (2)

AP for both sets and Y doubles the first two elements of X.

X={a,a+2,a+4,.....} spacing of 2
Y={2a,2a+4,2a+6....} spacing of 4 imposed on all the numbers since we have an A.P.

Notice we now have a relationship between the two sets. The spacing for Y is double that of X. Hence SUFF.
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Re: If sets X and Y have an equal number of elements, does set X have a [#permalink]
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The wording of this question is quite ambiguous and non-GMAT like:

1. Sets are not ordered by definition. So, "the first two elements in Set" doesn't make any sense.
2. "Twice greater" and "consistent throughout each set" is not the wording you'll see on the GMAT.

So, I wouldn't worry about this question at all.
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Re: If sets X and Y have an equal number of elements, does set X have a [#permalink]
Bunuel wrote:
The wording of this question is quite ambiguous and non-GMAT like:

1. Sets are not ordered by definition. So, "the first two elements in Set" doesn't make any sense.
2. "Twice greater" and "consistent throughout each set" is not the wording you'll see on the GMAT.

So, I wouldn't worry about this question at all.


Your absolutly right! That slipped my mind. Nonetheless the writer of the questions intent was that the set is sequntielly ordered. If that were the case the answer would be (C)

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