GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 16 Dec 2018, 23:35

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
  • 10 Keys to nail DS and CR questions

     December 17, 2018

     December 17, 2018

     06:00 PM PST

     07:00 PM PST

    Join our live webinar and learn how to approach Data Sufficiency and Critical Reasoning problems, how to identify the best way to solve each question and what most people do wrong.
  • R1 Admission Decisions: Estimated Decision Timelines and Chat Links for Major BSchools

     December 17, 2018

     December 17, 2018

     10:00 PM PST

     11:00 PM PST

    From Dec 5th onward, American programs will start releasing R1 decisions. Chat Rooms: We have also assigned chat rooms for every school so that applicants can stay in touch and exchange information/update during decision period.

M08-09

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51233
M08-09  [#permalink]

Show Tags

New post 15 Sep 2014, 23:36
2
4
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

60% (00:34) correct 40% (00:31) wrong based on 110 sessions

HideShow timer Statistics

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51233
Re M08-09  [#permalink]

Show Tags

New post 15 Sep 2014, 23:36
4
Official Solution:


The standard deviation of a set shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values. So, basically we can say that it in a sense measures the distance and the distance cannot be negative, which means that the standard deviation of any set is greater than or equal to zero: \(SD \ge 0\).

Next, the standard deviation of a set is zero if and only the set consists of identical numbers (or which is the same if the set consists of only one number).

(1) Each term of set \(T\) is positive. If \(T=\{5\}\) then then \(SD=0\) but if set \(T=\{5, 10\}\) then \(SD \gt 0\). Not sufficient.

(2) Set \(T\) consists of one term. Any set with only one term has the standard deviation equal to zero. Sufficient.


Answer: B
_________________

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

Intern
Intern
avatar
Joined: 09 Aug 2014
Posts: 12
Re M08-09  [#permalink]

Show Tags

New post 19 Mar 2015, 02:09
I think this question is good and helpful.
Current Student
avatar
Joined: 14 May 2014
Posts: 41
Schools: Broad '18 (WA)
GMAT 1: 700 Q44 V41
GPA: 3.11
GMAT ToolKit User Reviews Badge
Re: M08-09  [#permalink]

Show Tags

New post 24 Jul 2015, 07:07
Bunuel wrote:
Official Solution:


The standard deviation of a set shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values. So, basically we can say that it in a sense measures the distance and the distance cannot be negative, which means that the standard deviation of any set is greater than or equal to zero: \(SD \ge 0\).

Next, the standard deviation of a set is zero if and only the set consists of identical numbers (or which is the same if the set consists of only one number).

(1) Each term of set \(T\) is positive. If \(T=\{5\}\) then then \(SD=0\) but if set \(T=\{5, 10\}\) then \(SD \gt 0\). Not sufficient.

(2) Set \(T\) consists of one term. Any set with only one term has the standard deviation equal to zero. Sufficient.


Answer: B


dont we consider 0 as a positive no..? in that case both statements would be sufficient. pls help.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51233
Re: M08-09  [#permalink]

Show Tags

New post 24 Jul 2015, 07:09
riyazgilani wrote:
Bunuel wrote:
Official Solution:


The standard deviation of a set shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values. So, basically we can say that it in a sense measures the distance and the distance cannot be negative, which means that the standard deviation of any set is greater than or equal to zero: \(SD \ge 0\).

Next, the standard deviation of a set is zero if and only the set consists of identical numbers (or which is the same if the set consists of only one number).

(1) Each term of set \(T\) is positive. If \(T=\{5\}\) then then \(SD=0\) but if set \(T=\{5, 10\}\) then \(SD \gt 0\). Not sufficient.

(2) Set \(T\) consists of one term. Any set with only one term has the standard deviation equal to zero. Sufficient.


Answer: B


dont we consider 0 as a positive no..? in that case both statements would be sufficient. pls help.


You should brush up fundamentals.

ZERO:

1. 0 is an integer.

2. 0 is an even integer. An even number is an integer that is "evenly divisible" by 2, i.e., divisible by 2 without a remainder and as zero is evenly divisible by 2 then it must be even.

3. 0 is neither positive nor negative integer (the only one of this kind).

4. 0 is divisible by EVERY integer except 0 itself.

Check more here: number-properties-tips-and-hints-174996.html
_________________

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

Manager
Manager
User avatar
Joined: 11 Oct 2013
Posts: 106
Concentration: Marketing, General Management
GMAT 1: 600 Q41 V31
GMAT ToolKit User
Re M08-09  [#permalink]

Show Tags

New post 18 Dec 2015, 03:16
I think this is a high-quality question and I agree with explanation.
_________________

Its not over..

Intern
Intern
User avatar
Joined: 22 Aug 2014
Posts: 43
GMAT ToolKit User
M08-09  [#permalink]

Show Tags

New post 15 Jan 2016, 07:57
It is very tricky because of two crucial facts:
(1) SD is never negative. Think of its formula. SD is zero when single or same elements.
(2) Zero is neither positive nor negative.
Intern
Intern
avatar
Joined: 25 Dec 2015
Posts: 3
Re: M08-09  [#permalink]

Show Tags

New post 15 Jan 2016, 20:04
Bunuel wrote:
Official Solution:


The standard deviation of a set shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values. So, basically we can say that it in a sense measures the distance and the distance cannot be negative, which means that the standard deviation of any set is greater than or equal to zero: \(SD \ge 0\).

Next, the standard deviation of a set is zero if and only the set consists of identical numbers (or which is the same if the set consists of only one number).

(1) Each term of set \(T\) is positive. If \(T=\{5\}\) then then \(SD=0\) but if set \(T=\{5, 10\}\) then \(SD \gt 0\). Not sufficient.

(2) Set \(T\) consists of one term. Any set with only one term has the standard deviation equal to zero. Sufficient.


Answer: B



Are we not required to find whether the SD is positive or not and from the answer you have provided does not A give us SD>0 ?
So should not the answer be D instead of B ?
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 7108
Re: M08-09  [#permalink]

Show Tags

New post 15 Jan 2016, 20:16
soumya90 wrote:
Bunuel wrote:
Official Solution:


The standard deviation of a set shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values. So, basically we can say that it in a sense measures the distance and the distance cannot be negative, which means that the standard deviation of any set is greater than or equal to zero: \(SD \ge 0\).

Next, the standard deviation of a set is zero if and only the set consists of identical numbers (or which is the same if the set consists of only one number).

(1) Each term of set \(T\) is positive. If \(T=\{5\}\) then then \(SD=0\) but if set \(T=\{5, 10\}\) then \(SD \gt 0\). Not sufficient.

(2) Set \(T\) consists of one term. Any set with only one term has the standard deviation equal to zero. Sufficient.


Answer: B



Are we not required to find whether the SD is positive or not and from the answer you have provided does not A give us SD>0 ?
So should not the answer be D instead of B ?


Hi,
we are required to find out if SD is positive...
but we do not get a clear answer from A..
1) if there is only one element, or all elements are same say 5,5,5.. SD = 0..
2) if more than one and different, SD>0..

so SD can be 0, which is neither positive or negative or SD >0..
that is why insuff..
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


GMAT online Tutor

Intern
Intern
avatar
B
Joined: 22 Jun 2017
Posts: 25
Re M08-09  [#permalink]

Show Tags

New post 20 May 2018, 08:09
I think this is a high-quality question and I agree with explanation.
Intern
Intern
avatar
B
Joined: 22 Dec 2017
Posts: 9
Re: M08-09  [#permalink]

Show Tags

New post 07 Aug 2018, 08:43
Each term of set T is a multiple of 5. Is standard deviation of T positive?

(1) Each term of set T is positive

(2) T consists of one term
Hi,
the first statement is clearly not sufficient to answer the question about the SD.
The second SD=0 and 0 is neither positive nor negative , so that still didn't answer our question whether SD is positive or negative .
Please explain how statement 2 is sufficient.
GMAT Club Bot
Re: M08-09 &nbs [#permalink] 07 Aug 2018, 08:43
Display posts from previous: Sort by

M08-09

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Moderators: chetan2u, Bunuel



Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.