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

It is currently 20 Nov 2018, 23:59

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 November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • All GMAT Club Tests are Free and open on November 22nd in celebration of Thanksgiving Day!

     November 22, 2018

     November 22, 2018

     10:00 PM PST

     11:00 PM PST

    Mark your calendars - All GMAT Club Tests are free and open November 22nd to celebrate Thanksgiving Day! Access will be available from 0:01 AM to 11:59 PM, Pacific Time (USA)
  • Free lesson on number properties

     November 23, 2018

     November 23, 2018

     10:00 PM PST

     11:00 PM PST

    Practice the one most important Quant section - Integer properties, and rapidly improve your skills.

If M is a negative integer and K is a positive integer

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

Hide Tags

Manager
Manager
avatar
Joined: 07 Nov 2009
Posts: 247
If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 30 Jan 2012, 23:08
2
1
16
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

56% (01:31) correct 44% (01:50) wrong based on 613 sessions

HideShow timer Statistics

If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?

I. -1.5
II. -2
III. 0

(A) I only
(B) II only
(C) III only
(D) I and III only
(E) None
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50712
If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 30 Jan 2012, 23:56
15
10
rohitgoel15 wrote:
If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?
I. -1.5
II. -2
III. 0

(A) I only
(B) II only
(C) III only
(D) I and III only
(E) None


Important note: SD is always >=0. SD is 0 only when the list contains all identical elements (or which is same only 1 element).

So the answer is clearly E, none.

Answer: E.

To elaborate more: Standard deviation 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. Also if you look at the formula for the standard deviation you'll see that it's square root of some number (variance) and the square root can never be negative.

Check this for more: math-standard-deviation-87905.html

PS questions on SD: ps-questions-about-standard-deviation-85897.html
DS questions on SD: ds-questions-about-standard-deviation-85896.html

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

General Discussion
Senior Manager
Senior Manager
User avatar
Joined: 23 Oct 2010
Posts: 353
Location: Azerbaijan
Concentration: Finance
Schools: HEC '15 (A)
GMAT 1: 690 Q47 V38
GMAT ToolKit User
Re: M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 30 Jan 2012, 23:57
1
1
SD cant be negative. SD=0 if all the numbers are the same, or it is only one number in the set

So,E is the answ


hm...cant be before Bunuel :lol: trying, but still cant be hehe
_________________

Happy are those who dream dreams and are ready to pay the price to make them come true

I am still on all gmat forums. msg me if you want to ask me smth

Manager
Manager
avatar
Status: MBA Aspirant
Joined: 12 Jun 2010
Posts: 139
Location: India
Concentration: Finance, International Business
WE: Information Technology (Investment Banking)
Re: M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 31 Jan 2012, 20:36
Thanks Bunnel and Rohit for this good post and explanation
Director
Director
User avatar
Joined: 14 Dec 2012
Posts: 766
Location: India
Concentration: General Management, Operations
GMAT 1: 700 Q50 V34
GPA: 3.6
GMAT ToolKit User
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 12 Aug 2013, 02:49
rohitgoel15 wrote:
If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?

I. -1.5
II. -2
III. 0

(A) I only
(B) II only
(C) III only
(D) I and III only
(E) None


SD is always positive ...hence E.

IF the question would have been that what could be themedian.in that case answer would be C.
_________________

When you want to succeed as bad as you want to breathe ...then you will be successfull....

GIVE VALUE TO OFFICIAL QUESTIONS...



GMAT RCs VOCABULARY LIST: http://gmatclub.com/forum/vocabulary-list-for-gmat-reading-comprehension-155228.html
learn AWA writing techniques while watching video : http://www.gmatprepnow.com/module/gmat-analytical-writing-assessment
: http://www.youtube.com/watch?v=APt9ITygGss

Intern
Intern
avatar
Joined: 02 Aug 2015
Posts: 1
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 26 Aug 2015, 18:36
Bunuel wrote:
rohitgoel15 wrote:
If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?
I. -1.5
II. -2
III. 0

(A) I only
(B) II only
(C) III only
(D) I and III only
(E) None


Important note: SD is always >=0. SD is 0 only when the list contains all identical elements (or which is same only 1 element).

So the answer is clearly E, none.

Answer: E.

To elaborate more: Standard deviation 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. Also if you look at the formula for the standard deviation you'll see that it's square root of some number (variance) and the square root can never be negative.


Hope it helps.

_________________________________________________________________________________________




Hi,

I understood that SD cant be negative,
but SD can be zero, because SD <= 1/2 Range and if the range of a set is ZERO then SD will also be ZERO (I read this somewhere).

Please comment
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50712
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 26 Aug 2015, 22:47
gaganjyot11 wrote:
Bunuel wrote:
rohitgoel15 wrote:
If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?
I. -1.5
II. -2
III. 0

(A) I only
(B) II only
(C) III only
(D) I and III only
(E) None


Important note: SD is always >=0. SD is 0 only when the list contains all identical elements (or which is same only 1 element).

So the answer is clearly E, none.

Answer: E.

To elaborate more: Standard deviation 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. Also if you look at the formula for the standard deviation you'll see that it's square root of some number (variance) and the square root can never be negative.


Hope it helps.

_________________________________________________________________________________________




Hi,

I understood that SD cant be negative,
but SD can be zero, because SD <= 1/2 Range and if the range of a set is ZERO then SD will also be ZERO (I read this somewhere).

Please comment


SD is 0 only when the list contains all identical elements (or which is same only 1 element).

Check for more here: statistics-made-easy-all-in-one-topic-203966.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

Board of Directors
User avatar
P
Joined: 17 Jul 2014
Posts: 2645
Location: United States (IL)
Concentration: Finance, Economics
GMAT 1: 650 Q49 V30
GPA: 3.92
WE: General Management (Transportation)
GMAT ToolKit User Premium Member Reviews Badge
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 04 Dec 2015, 18:05
good one..very tricky
SD can never be negative, thus I and II out
SD will be 0 only when all the elements of the set are equal. thus, in our case, it can't be 0.
if m is -1 and k is 5, then SD would be between 1 and 2.
Intern
Intern
avatar
Joined: 31 Jan 2018
Posts: 16
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 18 Feb 2018, 01:07
-1.5,-2 cannot be the standard deviation,Because standard deviation can never be a negative number. SD>=0
SD=0 only when all the terms are equal.Irrespective of M and K all terms are not equal.So SD cannot be equal to 0 also.
So answer is none (E)
Intern
Intern
User avatar
B
Joined: 09 Jun 2016
Posts: 22
Reviews Badge
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 17 Jun 2018, 22:09
Bunuel wrote:
So, basically we can say that it in a sense measures the distance and the distance cannot be negative.

Hope it helps.


Hi Bunuel , understand that SD is always greater than or equal to 0. But you say that the square root can never be negative, there always seems to be some confusion regarding this. Can you please direct me to any material which helps in understanding when to consider +/- {square root} and when not to?
_________________

..................................................................................................................
micro-level speed, macro-level patience | KUDOS for the post ,shall be appreciated the most

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50712
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 17 Jun 2018, 22:16
abhishek911 wrote:
Bunuel wrote:
So, basically we can say that it in a sense measures the distance and the distance cannot be negative.

Hope it helps.


Hi Bunuel , understand that SD is always greater than or equal to 0. But you say that the square root can never be negative, there always seems to be some confusion regarding this. Can you please direct me to any material which helps in understanding when to consider +/- {square root} and when not to?


What is confusing there? Yes, SD as well as the even roots (such as square root of a number) is 0 or positive.
_________________

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

Veritas Prep GMAT Instructor
User avatar
P
Joined: 16 Oct 2010
Posts: 8576
Location: Pune, India
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 17 Jun 2018, 23:12
1
abhishek911 wrote:
Bunuel wrote:
So, basically we can say that it in a sense measures the distance and the distance cannot be negative.

Hope it helps.


Hi Bunuel , understand that SD is always greater than or equal to 0. But you say that the square root can never be negative, there always seems to be some confusion regarding this. Can you please direct me to any material which helps in understanding when to consider +/- {square root} and when not to?


Also, check out this post:
https://www.veritasprep.com/blog/2016/0 ... oots-gmat/
_________________

Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >

GMAT self-study has never been more personalized or more fun. Try ORION Free!

Intern
Intern
User avatar
B
Joined: 09 Jun 2016
Posts: 22
Reviews Badge
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 20 Jun 2018, 21:15
VeritasPrepKarishma wrote:
abhishek911 wrote:
Bunuel wrote:
So, basically we can say that it in a sense measures the distance and the distance cannot be negative.

Hope it helps.


Hi Bunuel , understand that SD is always greater than or equal to 0. But you say that the square root can never be negative, there always seems to be some confusion regarding this. Can you please direct me to any material which helps in understanding when to consider +/- {square root} and when not to?


Also, check out this post:
https://www.veritasprep.com/blog/2016/0 ... oots-gmat/


Thanks. This was the confusion!
_________________

..................................................................................................................
micro-level speed, macro-level patience | KUDOS for the post ,shall be appreciated the most

e-GMAT Representative
User avatar
P
Joined: 04 Jan 2015
Posts: 2203
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 20 Jun 2018, 21:36

Solution


Standard deviation formula is the mean of square of difference between mean and each element of the set which can either be positive or 0.

Image

Thus, SD can either be 0 or positive.
Now, standard deviation is 0 when x= x ̅ or when mean and all the elements of the set are equal.
However, in the set {-7, -5, -3, M, 0, 1, 3, K, 7} all the elements of the given set are not equal.
Thus, none of the given number can be the mean of the set {-7, -5, -3, M, 0, 1, 3, K, 7}.
Hence, the correct answer is option E.

Answer: E
_________________








Register for free sessions
Number Properties | Algebra |Quant Workshop

Success Stories
Guillermo's Success Story | Carrie's Success Story

Ace GMAT quant
Articles and Question to reach Q51 | Question of the week

Must Read Articles
Number Properties – Even Odd | LCM GCD | Statistics-1 | Statistics-2
Word Problems – Percentage 1 | Percentage 2 | Time and Work 1 | Time and Work 2 | Time, Speed and Distance 1 | Time, Speed and Distance 2
Advanced Topics- Permutation and Combination 1 | Permutation and Combination 2 | Permutation and Combination 3 | Probability
Geometry- Triangles 1 | Triangles 2 | Triangles 3 | Common Mistakes in Geometry
Algebra- Wavy line | Inequalities

Practice Questions
Number Properties 1 | Number Properties 2 | Algebra 1 | Geometry | Prime Numbers | Absolute value equations | Sets



| '4 out of Top 5' Instructors on gmatclub | 70 point improvement guarantee | www.e-gmat.com

CEO
CEO
User avatar
D
Joined: 11 Sep 2015
Posts: 3130
Location: Canada
Re: If M is a negative integer and K is a positive integer  [#permalink]

Show Tags

New post 11 Sep 2018, 09:10
Top Contributor
rohitgoel15 wrote:
If M is a negative integer and K is a positive integer, which of the following could be the standard deviation of a set {-7, -5, -3, M, 0, 1, 3, K, 7}?

I. -1.5
II. -2
III. 0

(A) I only
(B) II only
(C) III only
(D) I and III only
(E) None


Property 1: The standard deviation of a set of values is always greater than equal to 0
Property 2: If all values in a set are equal, the standard deviation of the set equals 0
Property 3: If the values in a set are NOT all equal, the standard deviation of the set is greater than 0

Now examine the statements...
I. -1.5 standard deviation cannot be negative.
II. -2 standard deviation cannot be negative.
III. 0 since the values are not all equal, the standard deviation cannot be zero.

Answer: E

Cheers,
Brent
_________________

Test confidently with gmatprepnow.com
Image

GMAT Club Bot
Re: If M is a negative integer and K is a positive integer &nbs [#permalink] 11 Sep 2018, 09:10
Display posts from previous: Sort by

If M is a negative integer and K is a positive integer

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


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®.