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M05-07

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New post 15 Sep 2014, 23:24
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Which of the following sets has the standard deviation greater than the standard deviation of set X={-19, -17, -15, -13, -11}

A={1, 3, 5, 7, 9}

B={2, 4, 6, 8, 10}

C={1, -1, -3, -5, -7}


A. Set A only
B. Set B only
C. Set C only
D. Sets A, B and C
E. None of the sets

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Re M05-07  [#permalink]

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New post 15 Sep 2014, 23:24
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Official Solution:


Which of the following sets has the standard deviation greater than the standard deviation of set X={-19, -17, -15, -13, -11}

A={1, 3, 5, 7, 9}

B={2, 4, 6, 8, 10}

C={1, -1, -3, -5, -7}


A. Set A only
B. Set B only
C. Set C only
D. Sets A, B and C
E. None of the sets


If we add or subtract a constant to each term in a set the standard deviation will not change.

Since each set can be obtained by adding some constant to each term of set X (20 for set A, 21 for set B and 12 for set C), the standard deviations of all sets are the same.


Answer: E
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Collection of Questions:
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M05-07  [#permalink]

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New post 07 May 2016, 16:57
Bunuel wrote:
Official Solution:


Which of the following sets has the standard deviation greater than the standard deviation of set X={-19, -17, -15, -13, -11}

A={1, 3, 5, 7, 9}

B={2, 4, 6, 8, 10}

C={1, -1, -3, -5, -7}


A. Set A only
B. Set B only
C. Set C only
D. Sets A, B and C
E. None of the sets


If we add or subtract a constant to each term in a set the standard deviation will not change.

Since each set can be obtained by adding some constant to each term of set X (20 for set A, 21 for set B and 12 for set C), the standard deviations of all sets are the same.


Answer: E


Can someone please explain (Bunuel if you're listening I'd appreciate the clarification) what exactly the logistics behind "adding some constant to each term" means? I presume like this, if Set x is [1, 2, 3, 4, 5] and adding 20 to it you get [21, 22, 23, 24, 25]. but I'm not sure how this relates either to the standard deviation or to why Bunuel chose different numbers for each set "20 for set A, 21 for set B and 12 for set C"
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Re: M05-07  [#permalink]

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New post 07 May 2016, 18:41
1
redfield wrote:
Bunuel wrote:
Official Solution:


Which of the following sets has the standard deviation greater than the standard deviation of set X={-19, -17, -15, -13, -11}

A={1, 3, 5, 7, 9}

B={2, 4, 6, 8, 10}

C={1, -1, -3, -5, -7}


A. Set A only
B. Set B only
C. Set C only
D. Sets A, B and C
E. None of the sets


If we add or subtract a constant to each term in a set the standard deviation will not change.

Since each set can be obtained by adding some constant to each term of set X (20 for set A, 21 for set B and 12 for set C), the standard deviations of all sets are the same.


Answer: E


Can someone please explain (Bunuel if you're listening I'd appreciate the clarification) what exactly the logistics behind "adding some constant to each term" means? I presume like this, if Set x is [1, 2, 3, 4, 5] and adding 20 to it you get [21, 22, 23, 24, 25]. but I'm not sure how this relates either to the standard deviation or to why Bunuel chose different numbers for each set "20 for set A, 21 for set B and 12 for set C"
...


the addition is being done to the SET in Question stem - set X={-19, -17, -15, -13, -11}
1) add 20 to each item of X {-19+20, -17+20, -15+20, -13+20, -11+20}
{1,3,5,7,9} SAME as A={1, 3, 5, 7, 9}

2) add 21 to each item of X {-19+21, -17+21, -15+21, -13+21, -11+21}
{2, 4, 6, 8, 10} SAME as B={2, 4, 6, 8, 10}

1) add 12 to each item of X {-19+12, -17+12, -15+12, -13+12, -11+12}
{1,-1,-3,-5,-7} SAME asC={1, -1, -3, -5, -7}
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Re M05-07  [#permalink]

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New post 26 Nov 2016, 03:54
I think this is a poor-quality question and I don't agree with the explanation. There is an error in Set C. The explanation says -19+12=-1? How is that possible?
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New post 26 Nov 2016, 04:14
saumyasharma wrote:
I think this is a poor-quality question and I don't agree with the explanation. There is an error in Set C. The explanation says -19+12=-1? How is that possible?


The question is fine.

X = {-19, -17, -15, -13, -11}

+12

C = {-7, -5, -3, -1, 1} (it's the same set as {1, -1, -3, -5, -7} but in different order).
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PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

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Re: M05-07  [#permalink]

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New post 05 Feb 2017, 06:20
Empowergmat Rich, Egmat cab you please explain the concept behind this question. How can I solve similar type of questions?
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M05-07  [#permalink]

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New post 26 Oct 2018, 11:52
Bunuel wrote:
Which of the following sets has the standard deviation greater than the standard deviation of set X={-19, -17, -15, -13, -11}

A={1, 3, 5, 7, 9}

B={2, 4, 6, 8, 10}

C={1, -1, -3, -5, -7}


A. Set A only
B. Set B only
C. Set C only
D. Sets A, B and C
E. None of the sets


Dear Bunuel,

Two sets dispersed equally along their mean have equal SD. Is this logic fine to solve this question?
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M05-07 &nbs [#permalink] 26 Oct 2018, 11:52
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