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

It is currently 21 Jan 2019, 20:17

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 January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
  • GMAT Club Tests are Free & Open for Martin Luther King Jr.'s Birthday!

     January 21, 2019

     January 21, 2019

     10:00 PM PST

     11:00 PM PST

    Mark your calendars - All GMAT Club Tests are free and open January 21st for celebrate Martin Luther King Jr.'s Birthday.
  • The winners of the GMAT game show

     January 22, 2019

     January 22, 2019

     10:00 PM PST

     11:00 PM PST

    In case you didn’t notice, we recently held the 1st ever GMAT game show and it was awesome! See who won a full GMAT course, and register to the next one.

If a, b, c, d are integers. Is standard deviation of a, b, c, d same

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

Hide Tags

 
Manager
Manager
avatar
D
Joined: 17 May 2015
Posts: 249
If a, b, c, d are integers. Is standard deviation of a, b, c, d same  [#permalink]

Show Tags

New post 27 Mar 2017, 06:00
2
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

70% (00:57) correct 30% (01:39) wrong based on 48 sessions

HideShow timer Statistics

If \(a, b, c, d\) are integers. Is standard deviation of \(a, b, c, d\) same as \(|a|, |b|, |c|, |d|\) ?

(1) Mean of \(a,b,c,d\) is 10.

(2) All numbers have the same sign.


Source: Self-made
DS Forum Moderator
avatar
P
Joined: 21 Aug 2013
Posts: 1432
Location: India
Premium Member
Re: If a, b, c, d are integers. Is standard deviation of a, b, c, d same  [#permalink]

Show Tags

New post 15 Jan 2018, 22:33
1
ganand wrote:
If \(a, b, c, d\) are integers. Is standard deviation of \(a, b, c, d\) same as \(|a|, |b|, |c|, |d|\) ?

(1) Mean of \(a,b,c,d\) is 10.

(2) All numbers have the same sign.


Source: Self-made



(1) Mean of a, b, c, d =10. Or their sum = 40.
Its possible that a=b=c=d=10, in which case |a|= |b|= |c|= |d| = 10. Here Std Dev of a,b,c,d = 0 and Std Dev of |a|,|b|,|c|,|d| is also 0. Both are equal.
Its also possible that a=b=30, c=d=-10. Here |a|=|b|=30, and |c|=|d|=10. Now the numbers a,b,c,d are 30, 30, -10, -10. While the numbers |a|,|b|,|c|,|d| are 30, 30, 10, 10 respectively. We can see that |a|,|b|,|c|,|d| are closer together as compared to a, b, c, d. So Std Dev of |a|,|b|,|c|,|d| will be smaller than that of a, b, c, d.

So Insufficient.


(2) All numbers are positive or all are negative. So in this case relative 'separation' among a,b,c,d will be same as that among |a|,|b|,|c|,|d|. So Std Dev will be same.
Eg, if a=2, b=3, c=4, d=5. Then |a|=2, |b|=3, |c|=4, |d|=5. Both set of numbers are exactly same. Std Dev will be equal.
If a=-2, b=-3, c=-4, d=-5, then |a|=2, |b|=3, |c|=4, |d|=5. The second set of numbers here is different from the first, but we can see that relative separation among the numbers is same. (distance between a&b is same as distance between |a| and |b|; distance between b&d is same as distance between |b| and |d|; and so on).

Sufficient.

Hence B answer
GMAT Club Bot
Re: If a, b, c, d are integers. Is standard deviation of a, b, c, d same &nbs [#permalink] 15 Jan 2018, 22:33
Display posts from previous: Sort by

If a, b, c, d are integers. Is standard deviation of a, b, c, d same

  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®.