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DS questions about standard deviation

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Re: DS questions about standard deviation [#permalink]

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New post 19 Dec 2016, 01:16
Hi Bunuel

Can you please post your explanation to Q7. Someone has explained it on page 1, but I'd like to see as to how you approach the question.

I am posting it here for your convenience again.

Set X consists of 8 integers. Is the standard deviation of set X equal to zero?

(1) The range of set X is equal to 3
(2) The mean of set X is equal to 5

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Re: DS questions about standard deviation [#permalink]

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New post 19 Dec 2016, 03:46
Keats wrote:
Hi Bunuel

Can you please post your explanation to Q7. Someone has explained it on page 1, but I'd like to see as to how you approach the question.

I am posting it here for your convenience again.

Set X consists of 8 integers. Is the standard deviation of set X equal to zero?

(1) The range of set X is equal to 3
(2) The mean of set X is equal to 5


Check here: set-x-consists-of-8-integers-is-the-standard-deviation-of-67893.html
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Collection of Questions:
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

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: DS questions about standard deviation [#permalink]

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New post 10 Jun 2017, 09:01
2. What is the standard deviation of Q, a set of consecutive integers?
(1) Q has 21 members.
(2) The median value of set Q is 20.

Hi Banuel,
I have a question on the the above SD, Everyone is saying answer is A,
But,
The question itself is giving the answer without need of choices, coz, he gave a set of consecutive integers, which means SD is 1. You cannot assume all are different or all are same. I don't need 1 or 2 to decide it right?

Can you please explain me.

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Re: DS questions about standard deviation [#permalink]

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New post 10 Jun 2017, 09:13
sasidharrs wrote:
2. What is the standard deviation of Q, a set of consecutive integers?
(1) Q has 21 members.
(2) The median value of set Q is 20.

Hi Banuel,
I have a question on the the above SD, Everyone is saying answer is A,
But,
The question itself is giving the answer without need of choices, coz, he gave a set of consecutive integers, which means SD is 1. You cannot assume all are different or all are same. I don't need 1 or 2 to decide it right?

Can you please explain me.


No, that's not correct. Sets with different number of elements will give different standard deviation. The SD of {1, 2} is different from that of {1, 2, 3, 4, 5, 6}
_________________

New to the Math Forum?
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Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
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

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

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DS questions about standard deviation [#permalink]

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New post 29 Oct 2017, 15:25
3. Lifetime of all the batteries produced by certain companies have a distribution which is symmetric about mean m. If the distribution has a standard deviation of d , what percentage of distribution is greater than m+d?
(1) 68 % of the distribution in the interval from m-d to m+d, inclusive
(2) 16% of the distribution is less than m-d

Hi Bunuel,

Can you please explain the solution of this question?
How are both statements Sufficient?

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Re: DS questions about standard deviation [#permalink]

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New post 29 Oct 2017, 19:31
radhikakhemka007 wrote:
3. Lifetime of all the batteries produced by certain companies have a distribution which is symmetric about mean m. If the distribution has a standard deviation of d , what percentage of distribution is greater than m+d?
(1) 68 % of the distribution in the interval from m-d to m+d, inclusive
(2) 16% of the distribution is less than m-d

Hi Bunuel,

Can you please explain the solution of this question?
How are both statements Sufficient?


The lifetime of all the batteries produced by a certain company in a year have a distribution that is symmetric about the mean m. If the distribution has a standard deviation of d, what percent of the distribution is greater than m+d?

Symmetric about the mean means that the shape of the distribution on the right and left side of the curve are mirror-images of each other.

(1) 68% of the distribution lies in the interval from m-d to m+d, inclusive --> 100%-68%=32% is less than m-d and more than m+d. As distribution is symmetric about the mean then exactly half of 32%, or 16%, would be more than m+d. Sufficient.

(2) 16% of the distribution is less than m-d --> again, as distribution is symmetric about the mean then exactly 16%, will be more than m+d. Sufficient.

Answer: D.

Hope it helps.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
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

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 135874 [0], given: 12715

Re: DS questions about standard deviation   [#permalink] 29 Oct 2017, 19:31

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