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

It is currently 23 Jul 2018, 06:57

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

Two different group of test takers received scores on the

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 26 Jul 2008
Posts: 4
Two different group of test takers received scores on the  [#permalink]

Show Tags

New post 06 Aug 2008, 18:45
Two different group of test takers received scores on the GYZ test. Group A had a normal distribution with mean of 460 and a Standard Deviation of 20. Group B had a normal distribution with mean of 520 and a Standard Deviation of 40. If each group has the same number of test takers, what fractio of test takers who scored below 440 belong to Group B ??

1/9

1/8

1/6

4/17

4/21.

Please help solve this...

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
1 KUDOS received
Director
Director
avatar
Joined: 23 Sep 2007
Posts: 761
Re: Standard Deviation and Normal Distribution  [#permalink]

Show Tags

New post 06 Aug 2008, 19:02
1
Guessing 4/21

this is somewhat of a convoluted question.

approx 68% falls between 1 SD of the average, so 32% outside of 1SD from average.
approx 95% falls between 2 SD of the average, so 5% outside of 2SD from average.

lets say 100 people in each group

in group A 16 people will be below 1 SD from average (32/2)

in group B 2.5 people will be below 2 SD from average (5/2)

So about 18.5 people (16 + 2.5) score lower than 440 from both groups

2.5/18.5 is somewhat closer to E than it it to D

not completely sure about my approximation.
Current Student
User avatar
Joined: 11 May 2008
Posts: 551
Re: Standard Deviation and Normal Distribution  [#permalink]

Show Tags

New post 06 Aug 2008, 20:13
i think A..
the logic as above is same,..
but i have got my result on the basis that 68% is within the 1 st deviation
28% next , and 4% on the last..
BTW, what is the correct values.?
some books say 68%,28%,4%
others say 68, 27,and 5... :roll:
Current Student
User avatar
Joined: 11 May 2008
Posts: 551
Re: Standard Deviation and Normal Distribution  [#permalink]

Show Tags

New post 08 Aug 2008, 10:11
hello... can the einsteins pitch in???
Director
Director
avatar
Joined: 27 May 2008
Posts: 530
Re: Standard Deviation and Normal Distribution  [#permalink]

Show Tags

New post 08 Aug 2008, 11:13
First ot all i dont think its a GMAT question.. we are not supposed to know the properties of normal distribution..

i agree with gmatnub's approach .. the answer should be 2.5/18.5 actually 2.2/18 to be more accurate

closest option is B 1/8.
Expert Post
GMAT Tutor
avatar
S
Joined: 24 Jun 2008
Posts: 1345
Re: Standard Deviation and Normal Distribution  [#permalink]

Show Tags

New post 08 Aug 2008, 18:17
I haven't even read the question (but I trust Durgesh :) ), but you do not need to know anything about the properties of a normal distribution for the GMAT- and you definitely don't need to know what percentage of data points fall within one or two standard deviations in a normally distributed set of data.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

SVP
SVP
User avatar
Joined: 29 Aug 2007
Posts: 2425
Re: Standard Deviation and Normal Distribution  [#permalink]

Show Tags

New post 08 Aug 2008, 18:23
IanStewart wrote:
I haven't even read the question (but I trust Durgesh :) ), but you do not need to know anything about the properties of a normal distribution for the GMAT- and you definitely don't need to know what percentage of data points fall within one or two standard deviations in a normally distributed set of data.


I am not sure about to what extent we need to understand these properties, but it won't harm if we remember these properties as well.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

_________________

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


GT

Re: Standard Deviation and Normal Distribution &nbs [#permalink] 08 Aug 2008, 18:23
Display posts from previous: Sort by

Two different group of test takers received scores on the

  post reply Question banks Downloads My Bookmarks Reviews Important topics  

Moderator: chetan2u

Events & Promotions

PREV
NEXT


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®.