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If x and y are the standard deviations of two different data sets, is

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If x and y are the standard deviations of two different data sets, is  [#permalink]

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New post 29 Apr 2018, 08:24
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If x and y are the standard deviations of two different data sets, is x > y?

(1) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.
(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.

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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: If x and y are the standard deviations of two different data sets, is  [#permalink]

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New post 29 Apr 2018, 23:11
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1
Bunuel wrote:
If x and y are the standard deviations of two different data sets, is x > y?

(1) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.
(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.


Hi,

Standard Deviation(SD) is a measure of dispersion of a set of data from its mean. It is the square root of the variance => the minimum value of SD will always be 0.

For more please refer: https://gmatclub.com/forum/math-standar ... 87905.html

Now, let's solve the question.

If x and y are the standard deviations of two different data sets, is x > y?

(1) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.

Since all the data points are same(i.e.50) => x (SD) = 0. Hence, x can't be greater than y. Sufficient.

(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.

Definitely value of y is greater than 0, and we have no information about the value of x. Hence, we can't determine whether x is greater than y or not. Insufficient.

Answer: (A).

Thanks.
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Re: If x and y are the standard deviations of two different data sets, is  [#permalink]

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New post 16 May 2018, 06:01
1
) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.

Standard Deviation(SD) is a measure of dispersion of a set of data from its mean. It is the square root of the variance => the minimum value of SD will always be 0.

In this case x=0

Even if y also have same values in its set and y=0

For the same 0>0 not valid

So x>y will be No in every case
So sufficient


(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.

Y has got some value here
But no info about x
So can't say. Insufficient

A is answer
Give kudos if it helps

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Re: If x and y are the standard deviations of two different data sets, is  [#permalink]

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New post 27 Jun 2018, 19:39
ganand wrote:
Bunuel wrote:
If x and y are the standard deviations of two different data sets, is x > y?

(1) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.
(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.


Hi,

Standard Deviation(SD) is a measure of dispersion of a set of data from its mean. It is the square root of the variance => the minimum value of SD will always be 0.

For more please refer: https://gmatclub.com/forum/math-standar ... 87905.html

Now, let's solve the question.

If x and y are the standard deviations of two different data sets, is x > y?

(1) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.

Since all the data points are same(i.e.50) => x (SD) = 0. Hence, x can't be greater than y. Sufficient.

(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.

Definitely value of y is greater than 0, and we have no information about the value of x. Hence, we can't determine whether x is greater than y or not. Insufficient.

Answer: (A).

Thanks.


Hi..

Here we are assuming that the value of Y is greater..without assessing the infor of Y, How can we assume that X >Y?

It can also be the case where the SD of Y could also be 0

Please help..
Math Expert
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Joined: 02 Sep 2009
Posts: 51215
Re: If x and y are the standard deviations of two different data sets, is  [#permalink]

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New post 27 Jun 2018, 20:01
zanaik89 wrote:
ganand wrote:
Bunuel wrote:
If x and y are the standard deviations of two different data sets, is x > y?

(1) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.
(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.


Hi,

Standard Deviation(SD) is a measure of dispersion of a set of data from its mean. It is the square root of the variance => the minimum value of SD will always be 0.

For more please refer: https://gmatclub.com/forum/math-standar ... 87905.html

Now, let's solve the question.

If x and y are the standard deviations of two different data sets, is x > y?

(1) x is the standard deviation of the data set 50, 50, 50, 50, 50, 50, 50, 50 50, 50, 50.

Since all the data points are same(i.e.50) => x (SD) = 0. Hence, x can't be greater than y. Sufficient.

(2) y is the standard deviation of the data set 40, 42, 44, 46, 48, 50, 52, 54 56, 58, 60.

Definitely value of y is greater than 0, and we have no information about the value of x. Hence, we can't determine whether x is greater than y or not. Insufficient.

Answer: (A).

Thanks.


Hi..

Here we are assuming that the value of Y is greater..without assessing the infor of Y, How can we assume that X >Y?

It can also be the case where the SD of Y could also be 0

Please help..


The standard deviation is always more than or equal to zero: \(SD \ge 0\). SD is 0 only when the list contains all identical elements (or which is same only 1 element).

(1) implies that x = 0. So, x cannot be more than y because y is 0 or more (so we have a NO answer to the question). If y = 0 too, then x =y, so the answer is still NO.
_________________

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

GMAT Club Bot
Re: If x and y are the standard deviations of two different data sets, is &nbs [#permalink] 27 Jun 2018, 20:01
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