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Is the standard deviation of set A > standard deviation of set B?

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Is the standard deviation of set A > standard deviation of set B?  [#permalink]

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New post 21 Aug 2018, 20:55
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A
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C
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Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.

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Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

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New post 22 Aug 2018, 20:33
PKN wrote:
PKN wrote:
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.


Question stem:- Is \(SD_{A}>SD_{B}\)?

Note:- If you multiply the numbers on a list by any values (other than ±1), or if you raise the numbers on a list to a power, that always changes the standard deviation. Multiplying changes the spacing on the list. In particular, if you multiply each number by k, then you multiply the standard deviation by |k|.

St1:- Set A consists of consecutive multiples of 10.
Or A={10,20,30,40,....,10n}
No info on Set B.
Insufficient.

St2:- Set B consists of consecutive multiples of 2
Or, B={2,4,6,8,....,2n}
No info on Set A.
Insufficient.

Combined, Set A can be written as A={5*1,5*2,5*33,5*4,.........} or each term of the set B when multiplied by a constant 5 yield set A.
So, SD of set A=5* SD of set B
Hence \(SD_{A}>SD_{B}\)

Ans. (C)


Hi chetan2u,
Could you please guide me where I am wrong in my explanation above?

Thanking you in advance.



Hi..

You have gone wrong in taking number of elements of each.

Combined..
Set A consists of consecutive multiple of 10, say 10,20
Set B = {2,4,6}
SD of A> SD of B..

But if set A={10,20}
And set B = {2,4,6,8,10,........50}
SD of A<SD of B

Different answers possible..
Hence E
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Is the standard deviation of set A > standard deviation of set B?  [#permalink]

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New post 21 Aug 2018, 21:34
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.



Standard deviation is 0,if all elements are equal.
Also Std deviation is always greater than or equal to zero.
Since by one std deviation we cannot tell for sure if it is less or greater than other deviation,both statements are required.

Ans :C
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Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

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New post 21 Aug 2018, 21:39
Statement 1 doesn't give any info about Set B. Hence insufficient.
Statement 2 doesn't give any info about Set A. Hence insufficient.

Combining both we can say that SD of A will always be greater than B.Irrespective of the number of elements in each set.

C is the answer.

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Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

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New post 21 Aug 2018, 21:49
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.


Question stem:- Is \(SD_{A}>SD_{B}\)?

Note:- If you multiply the numbers on a list by any values (other than ±1), or if you raise the numbers on a list to a power, that always changes the standard deviation. Multiplying changes the spacing on the list. In particular, if you multiply each number by k, then you multiply the standard deviation by |k|.

St1:- Set A consists of consecutive multiples of 10.
Or A={10,20,30,40,....,10n}
No info on Set B.
Insufficient.

St2:- Set B consists of consecutive multiples of 2
Or, B={2,4,6,8,....,2n}
No info on Set A.
Insufficient.

Combined, Set A can be written as A={5*1,5*2,5*33,5*4,.........} or each term of the set B when multiplied by a constant 5 yield set A.
So, SD of set A=5* SD of set B
Hence \(SD_{A}>SD_{B}\)

Ans. (C)
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PKN

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Director
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Re: Is the standard deviation of set A > standard deviation of set B?  [#permalink]

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New post 22 Aug 2018, 20:03
PKN wrote:
Bunuel wrote:
Is the standard deviation of set A > standard deviation of set B?

(1) Set A consists of consecutive multiples of 10.

(2) Set B consists of consecutive multiples of 2.


Question stem:- Is \(SD_{A}>SD_{B}\)?

Note:- If you multiply the numbers on a list by any values (other than ±1), or if you raise the numbers on a list to a power, that always changes the standard deviation. Multiplying changes the spacing on the list. In particular, if you multiply each number by k, then you multiply the standard deviation by |k|.

St1:- Set A consists of consecutive multiples of 10.
Or A={10,20,30,40,....,10n}
No info on Set B.
Insufficient.

St2:- Set B consists of consecutive multiples of 2
Or, B={2,4,6,8,....,2n}
No info on Set A.
Insufficient.

Combined, Set A can be written as A={5*1,5*2,5*33,5*4,.........} or each term of the set B when multiplied by a constant 5 yield set A.
So, SD of set A=5* SD of set B
Hence \(SD_{A}>SD_{B}\)

Ans. (C)


Hi chetan2u,
Could you please guide me where I am wrong in my explanation above?

Thanking you in advance.
_________________

Regards,

PKN

Rise above the storm, you will find the sunshine

Re: Is the standard deviation of set A > standard deviation of set B? &nbs [#permalink] 22 Aug 2018, 20:03
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