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How many elements are there in Set A? 1) Frequency of each

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by GMATinsight » Thu Oct 05, 2017 8:39 pm
How many elements are there in Set A?

1) Frequency of each element in the set A is 1
2) Standard Deviation of Set A is NOT Positive

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Answer: Option C
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Source: — Data Sufficiency |

by Jay@ManhattanReview » Thu Oct 05, 2017 9:26 pm
GMATinsight wrote:How many elements are there in Set A?

1) Frequency of each element in the set A is 1
2) Standard Deviation of Set A is NOT Positive

Source: https://www.GMATinsight.com

Answer: Option C
(1) The frequency of each element in the set A is 1.

If Set A is {2, 3, 4, 5}, the answer is 4; however, if Set A is {2, 3, 4}, the answer is 3. No unique answer. Insufficient.

(2) Standard Deviation of Set A is NOT Positive.

Since the standard deviation is a non-negative number, and it is given that SD is not positive, it means that SD = 0.

A set with SD will have all the equal elements in it.

If Set A is {2, 2, 2}, the answer is 3; however, if Set A is {2, 2}, the answer is 2. No unique answer. Insufficient.

(1) and (2) combined

From (1) and (2) Set A can be {1), {2}, {-1/2}, or anything having only ONE element in it. The answer is 1. Sufficient.

The correct answer: C

Hope this helps!

-Jay

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