It is currently Tue Feb 07, 2012 3:46 am




   Post new topic Reply to topic      [ 20 posts ]  Bookmark and Share Oldest Best Reply
Author Message
  M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Fri Mar 13, 2009 10:29 am 
Offline
Intern
Intern

Joined: Sun Jan 04, 2009
Posts: 12
Schools: not sure
Followers: 0

Kudos (?): 0 (0), given: 0

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

1. All elements of set T are positive
2. The range of set T is 0

[Reveal] Spoiler: OA
B

Source: GMAT Club Tests - hardest GMAT questions

Can anyone explain this? Thanks!


  Profile  
 
Kaplan Promo CodeKnewton GMAT Discount CodesVeritas Prep GMAT Discount Codes
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Mon Mar 16, 2009 8:28 am 
Offline
Manager
Manager

Joined: Sat Jul 07, 2007
Posts: 169
Followers: 1

Kudos (?): 10 (2), given: 0

GMAT Tests User
jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


Answer is B).

S1) All elements of set T are positive. - In this case you can have either 0 or positive, SD. (example: (3,3) or (3,6) and so it is not sufficient).

S2) The range of set T is 0, range is (max - min) and so it is zero only if max and min are same (example: 3, 3, 3, 3 set, in this case range will be zero and so standard deviation will be zero too and so S2) answer this question and sufficient.


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Sun Apr 05, 2009 9:30 am 
Offline
CEO
CEO
User avatar

Joined: Wed Aug 29, 2007
Posts: 2944
Followers: 27

Kudos (?): 285 (1), given: 19

GMAT Tests User
jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


It should be B however set T cannot have elements other than that are divisible by 3.

Remeber: SD and range can never be -ve.

1: The elements in set T could be [2, 3, 4, 5] or [3, 6, 9, 12, 15] or [3, 3, 3, 3, 3]. The SD could be 0 or +ve.
2: If the range of the set T is 0, then the elements in set T could be [-3, -3, -3, -3] or [3, 3, 3, 3, 3] or [6, 6, 6, 6, 6]. in any case the SD is 0, which is not a positive. Hence suff..

_________________
Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html


GT


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Wed Mar 16, 2011 4:29 am 
Offline
Math Forum Moderator

Joined: Mon Dec 20, 2010
Posts: 2239
Followers: 88

Kudos (?): 544 (1), given: 375

GMAT Tests User
Yalephd wrote:
What does the abbreviation -ve mean?

GMAT TIGER wrote:
jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


It should be B however set T cannot have elements other than that are divisible by 3.

Remeber: SD and range can never be -ve.

1: The elements in set T could be [2, 3, 4, 5] or [3, 6, 9, 12, 15] or [3, 3, 3, 3, 3]. The SD could be 0 or +ve.
2: If the range of the set T is 0, then the elements in set T could be [-3, -3, -3, -3] or [3, 3, 3, 3, 3] or [6, 6, 6, 6, 6]. in any case the SD is 0, which is not a positive. Hence suff..


-ve: Negative. All numbers less than 0 on the number line.
+ve: Positive. All numbers greater than 0 on the number line.

Standard Deviation can never be -ve. It can be 0 or +ve.

Set contains certain number of even integers. Integers should be divisible by 6. Set can have -12,0,6,12,18

5 numbers; all even and divisible by 3.

1. All elements are +ve.

"6,12,18" will result in +ve standard deviation
"6,6,6" will result in 0 standard deviation because all numbers are equal.

Not sufficient.

2. The range of the set is 0.

If the range of a set is 0, all the elements are equal.

Set can be; -12,-12,-12. Standard deviation=0
Or
0,0,0. Standard deviation=0
Or
6,6,6. Standard deviation=0

Since, all the numbers of the set are equal, the standard deviation will be 0.
Sufficient.

Ans: "B"

_________________
~fluke


  Profile E-mail  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Tue Mar 17, 2009 8:46 am 
Offline
Manager
Manager
User avatar

Joined: Mon Dec 15, 2008
Posts: 53
Schools: HBS(08) - Ding. HBS, Stanford, Kellogg, Tuck, Stern, all dings. Yale - Withdrew App. Emory Executive -- Accepted, Matriculated, Withdrewed (yes, I spelled it wrong on purpose). ROSS -- GO BLUE 2011.
Followers: 1

Kudos (?): 12 (0), given: 1

jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


Standard deviation = the square root of something that has been squared, which must be positive, unless of course it's zero.

S1 -- Insufficient. the SD could be 0 or some other number. 0 is not positive, so insufficent to answer the question.

Example --> if the set is {0,0,0,0} SD is zero. If the set is {2,4} SD is 1
S2 -- Sufficient. All the numbers in the set are the same, therefore SD is 0, there the answer is always no.

{0,0,0,0} SD is 0. {2,2} SD is 0....

B


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Fri Mar 20, 2009 12:09 pm 
Offline
Intern
Intern

Joined: Fri Mar 06, 2009
Posts: 2
Followers: 0

Kudos (?): 0 (0), given: 0

GMAT Tests User
IMO, the answer should be A. Here's the reasoning :

1. They have clearly given that all the members of the set are positive. Hence, 0 is out (0 does not bear a sign). Even if the members of the set are negative, their deviation will always be +ve. Hence A is sufficient.

2. The members of the set could all be 0. Hence the deviation will be 0. At the same time, all the members of the set can be the same. e.g. 2. In such cases, the range will be 0. So option 2 does not give any additional information. The only scenario that the deviation will not be positive is if the deviation is 0 (in case of all zeros). Hence B is not sufficient.

Ans : A


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Thu Mar 26, 2009 5:25 am 
Offline
VP
VP
User avatar

Joined: Tue Apr 01, 2008
Posts: 1011
Location: Bangalore, Baroda
Followers: 7

Kudos (?): 101 (0), given: 18

GMAT Tests User
IMO C.
1) Set can be {6,6} or {6,9,12} so deviation can be 0 or some +ve num. Not suff.
2) Set can be {0,0} or {6,6} or {-6,0,6,9} => deviation can be zero,-ve or +ve.

Combining, all +ve even numbers divisible by 3 are there and all numbers are same. eg{6,6} => deviation is 0 which is not positive.

What is OA?
jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Sun Apr 05, 2009 2:17 am 
Offline
VP
VP
User avatar

Joined: Tue Apr 01, 2008
Posts: 1011
Location: Bangalore, Baroda
Followers: 7

Kudos (?): 101 (0), given: 18

GMAT Tests User
Hi jenyang5268, wat is OA?


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Tue Jan 05, 2010 5:48 pm 
Offline
Manager
Manager

Joined: Wed Jul 08, 2009
Posts: 191
Followers: 0

Kudos (?): 9 (0), given: 26

gmatdreamz wrote:
IMO, the answer should be A. Here's the reasoning :

1. They have clearly given that all the members of the set are positive. Hence, 0 is out (0 does not bear a sign). Even if the members of the set are negative, their deviation will always be +ve. Hence A is sufficient.

2. The members of the set could all be 0. Hence the deviation will be 0. At the same time, all the members of the set can be the same. e.g. 2. In such cases, the range will be 0. So option 2 does not give any additional information. The only scenario that the deviation will not be positive is if the deviation is 0 (in case of all zeros). Hence B is not sufficient.

Ans : A


1, Even if all members of the set are positive, the standard deviation can still be 0.


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Wed Jan 06, 2010 4:55 am 
Online
GMAT Club Legend
GMAT Club Legend
User avatar

Joined: Wed Sep 02, 2009
Posts: 5211
Followers: 617

Kudos (?): 3361 (0), given: 148

GMAT Tests User
Top Member of the Month
Some tips:

SD\geq0, Standard deviation ALWAYS greater or equal to zero.

Standard deviation equals to zero if and only set consists of identical number(s) (special case set has only one element), eg {2,2,2,2}{-5,-5}{3}.

Range=0 --> SD=0, as when range=0 either we have the set of identical elements or set has only one element.

_________________
RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory

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 - JUST ADDED!!!; 8 12 Easy Pieces (or not?) - NEWEST SET OF TRICKY QUESTIONS!!!

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 - JUST ADDED!!!; 8 The Discreet Charm of the DS - Latest set of tough DS questions


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Thu Mar 11, 2010 9:50 am 
Offline
Intern
Intern

Joined: Thu Mar 11, 2010
Posts: 4
Followers: 0

Kudos (?): 0 (0), given: 0

RahlowJenkins wrote:
jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


Standard deviation = the square root of something that has been squared, which must be positive, unless of course it's zero.

S1 -- Insufficient. the SD could be 0 or some other number. 0 is not positive, so insufficent to answer the question.

Example --> if the set is {0,0,0,0} SD is zero. If the set is {2,4} SD is 1
S2 -- Sufficient. All the numbers in the set are the same, therefore SD is 0, there the answer is always no.

{0,0,0,0} SD is 0. {2,2} SD is 0....

B



The definition SET in mathematics (according to wikipedia ) is:
A set is a collection of distinct objects, considered as an object in its own right.

Note the word "DISTINCT", in the set given example the elements are identical, thus this doesn't fit the definition of a set.

So, the answer should be B, since the elements in the set should be multiples of 6, and they must be distinct.

S1 alone: They can be {6} or {6,12,18}, in the first case SD is 0 and in the second case SD is positive

S2 alone: Range = 0 implies that the max element = min element in the set, since the elements are distinct, the set contains only one element. The SD in that case will always be 0, so not positive.


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Fri Mar 12, 2010 4:58 am 
Offline
Senior Manager
Senior Manager

Joined: Mon Feb 01, 2010
Posts: 298
Followers: 1

Kudos (?): 25 (0), given: 2

GMAT Tests User
jenyang5268 wrote:
Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

1. All elements of set T are positive
2. The range of set T is 0

[Reveal] Spoiler: OA
B

Source: GMAT Club Tests - hardest GMAT questions

Can anyone explain this? Thanks!


Its B.

Stmt 1: SD can be +ve or zero so can't decide on SD hence insufficient.
Stmt 2: Range is zero so SD has to be zero so sufficient.


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Sun Mar 14, 2010 2:27 am 
Offline
Senior Manager
Senior Manager

Joined: Fri Mar 05, 2010
Posts: 260
Followers: 1

Kudos (?): 13 (0), given: 8

B is my answer


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Thu Mar 18, 2010 9:19 am 
Offline
Senior Manager
Senior Manager

Joined: Mon Dec 21, 2009
Posts: 364
Concentration: Entrepreneurship, Finance
Followers: 3

Kudos (?): 61 (0), given: 10

GMAT Tests User
jenyang5268 wrote:
Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

1. All elements of set T are positive
2. The range of set T is 0


1. 0, 0, are even integers divisible by 3. SD = 0
Also, 0, 6 are even integers divisible by 3. SD is +ve
considering both cases, stmt1 is INSUFF

2. The sets {-6, -6}, {0, 0}, and {12, 12} all have range 0. Irrespective of whether the elements
are +ve or -ve, a unique value in the set gives SD 0.....so, SUFFICIENT
Hence, OA = B.

_________________
KUDOS me if you feel my contribution has helped you.


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Fri Mar 19, 2010 6:32 am 
Offline
Senior Manager
Senior Manager
User avatar

Joined: Sun Dec 13, 2009
Posts: 283
Followers: 2

Kudos (?): 51 (0), given: 13

GMAT Tests User
+1 for B with the above explanation.

_________________
My debrief: done-and-dusted-730-q49-v40


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Mon Sep 06, 2010 11:34 pm 
Offline
Manager
Manager

Joined: Mon Jul 12, 2010
Posts: 151
Followers: 1

Kudos (?): 1 (0), given: 3

B.


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Wed Mar 16, 2011 4:19 am 
Offline
Manager
Manager

Joined: Tue Aug 03, 2010
Posts: 98
GMAT Date: 08-08-2011
Followers: 1

Kudos (?): 5 (0), given: 63

What does the abbreviation -ve mean?

GMAT TIGER wrote:
jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


It should be B however set T cannot have elements other than that are divisible by 3.

Remeber: SD and range can never be -ve.

1: The elements in set T could be [2, 3, 4, 5] or [3, 6, 9, 12, 15] or [3, 3, 3, 3, 3]. The SD could be 0 or +ve.
2: If the range of the set T is 0, then the elements in set T could be [-3, -3, -3, -3] or [3, 3, 3, 3, 3] or [6, 6, 6, 6, 6]. in any case the SD is 0, which is not a positive. Hence suff..


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Wed Mar 16, 2011 7:31 am 
Offline
SVP
SVP
User avatar

Joined: Tue Nov 16, 2010
Posts: 1662
Location: Singapore
Concentration: Strategy, Technology
Followers: 12

Kudos (?): 137 (0), given: 27

GMAT Tests User
The answer is B.

_________________
Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Wed Mar 16, 2011 9:37 am 
Offline
Manager
Manager

Joined: Fri Feb 11, 2011
Posts: 203
Followers: 1

Kudos (?): 0 (0), given: 0

GMAT Tests User
answer is B


  Profile  
 
  Re: M25 Q10 Data Sufficiency Problem [#permalink]
New postPosted: Wed Mar 16, 2011 8:08 pm 
Offline
Manager
Manager

Status: A continuous journey of self-improvement is essential for every person -Socrates
Joined: Sun Jan 02, 2011
Posts: 87
Followers: 1

Kudos (?): 0 (0), given: 14

patedhav wrote:
jenyang5268 wrote:
M25, Q10 Data Sufficiency:

Set T consists of a certain number of even integers divisible by 3. Is standard deviation of T positive?

S1) All elements of set T are positive
S2) The range of set T is 0

Can anyone explain this? Thanks!


Answer is B).

S1) All elements of set T are positive. - In this case you can have either 0 or positive, SD. (example: (3,3) or (3,6) and so it is not sufficient).

S2) The range of set T is 0, range is (max - min) and so it is zero only if max and min are same (example: 3, 3, 3, 3 set, in this case range will be zero and so standard deviation will be zero too and so S2) answer this question and sufficient.



Short and crisp explanation that too before OA. +1.


  Profile  
 
Online
gmatclubot
Display posts from previous:  Sort by  

Get Started:
Two Free Trial Tests

Get All GMATClub Tests

GMAT Heavy Lifting

GMAT Club Tests

Post new topic Reply to topic  [ 20 posts ] 

 Similar topics   Author   Replies   Views   Last post 
Data Sufficiency Problem

in GMAT Data Sufficiency (DS)

mirzohidjon

6

507

Thu Aug 27, 2009 4:48 am

Data sufficiency Geometry problem

in GMAT Club Tests

ksharma12

1

246

Thu Apr 15, 2010 11:14 am

Data Sufficiency problem

in GMAT Data Sufficiency (DS)

ctgmat123

7

1204

Mon Jun 14, 2010 4:50 pm

Data Sufficiency-word problem

in GMAT Data Sufficiency (DS)

rite2deepti

6

642

Mon Dec 13, 2010 5:53 am

Data Sufficiency Problem Help

in GMAT Data Sufficiency (DS)

rk0900

1

543

Fri Jul 08, 2011 10:12 am





Who is online

Users browsing this forum: No registered users and 0 guests


Search for:
Jump to:




GMAT Club MBA Forum Home | About | Privacy Policy | Terms and Conditions | GMAT Club Rules | Contact | Sitemap
Powered by phpBB © phpBB Group and phpBB SEO
Kindly note that GMAT (C) is a registered trademark of the Graduate Management Admission Council, and this site has neither been reviewed nor endorsed by GMAC.