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

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How many elements are there in Set A? 1) Frequency of each element in  [#permalink]

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05 Oct 2017, 07:08
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Difficulty:

25% (medium)

Question Stats:

67% (00:46) correct 33% (00:34) wrong based on 36 sessions

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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: http://www.GMATinsight.com

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How many elements are there in Set A? 1) Frequency of each element in  [#permalink]

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05 Oct 2017, 07:46
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: http://www.GMATinsight.com

Statement 1:set can be {1,2,3...} or {1}. in either case frequency is 1 but no of elements are different. Hence insufficient

Statement 2: implies St. Dvi is 0 because standard deviation cannot be negative, it is either positive or 0. Note standard deviation is the square root of variance, hence cannot be negative. so in Set A all elements are equal i.e {1,1,1,1....} or {1}. In either case no of elements are different. hence Insufficient

Combining 1 & 2,it is clear that the set A has only One element. Hence Sufficient

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Re: How many elements are there in Set A? 1) Frequency of each element in  [#permalink]

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18 Mar 2019, 00:00
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: http://www.GMATinsight.com

From statement 1 : the set can be [1,2,5,6,7] or [3,4,5] nothing conclusive.
From statement 2 : Standard deviation =0 since standard deviation cannot be negative. So that means all the element in the set are the same i.e [2,2,2] or [2]. But we cannot infer anything about the number of elements.

Comibining 1 and 2:

Frequency is 1 and the elements are same. Hence number of elements has to 1.

Re: How many elements are there in Set A? 1) Frequency of each element in   [#permalink] 18 Mar 2019, 00:00
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