Set A consists of 8 different integers from the list {1,3,5,

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Set A consists of 8 different integers from the list {1,3,5,7,9,11,13,15,17,19}. What is standard deviation of the set A?

1. Set A does not include 11.
2. The average of the numbers in the given list is equal to the average of numbers in set A.

OA C.

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by Jay@ManhattanReview » Sat Sep 08, 2018 8:45 pm

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AAPL wrote:e-GMAT

Set A consists of 8 different integers from the list {1,3,5,7,9,11,13,15,17,19}. What is standard deviation of the set A?

1. Set A does not include 11.
2. The average of the numbers in the given list is equal to the average of numbers in set A.

OA C.
There are 10 integers in the set {1,3,5,7,9,11,13,15,17,19}; out of which 8 integeras are to be chosen.

If we freeze on the unique 8 integers, we get the value of standard deviation. Note that the computation of standard deviation is out of the scope of the GMAT; however, since this is a DS question, and we have to answer whether there is a unique answer to the question.

Let's take each statement one by one.

1. Set A does not include 11.

One more integer is not known. It will impact the value of SD. Insufficient.

2. The average of the numbers in the given list is equal to the average of numbers in set A.

Average of the given set {1,3,5,7,9,11,13,15,17,19} = 10

Thus, the average of Set A = 10.

We can exclude one of the four possible groups: (1, 19), (3, 17), (5, 15), (7, 13), and (9, 11).

It will impact the value of SD. Insufficient.

(1) and (2) together

Since Statement states that 11 is not there in the set, that means 9 is also not there, thus, Set A: {1,3,5,7,13,15,17,19}. Unique value of SD can be computed. Sufficient.

The correct answer: C

Hope this helps!

-Jay
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