It is currently 17 Dec 2017, 23:19

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

Events & Promotions in June
Open Detailed Calendar

70 75 80 85 90 105 105 130 130 130 The list shown consist of

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42670

Kudos [?]: 136007 [0], given: 12723

Re: 70 75 80 85 90 105 105 130 130 130 The list shown consist of [#permalink]

Show Tags

New post 04 Jan 2013, 04:59
Sachin9 wrote:
Bunuel wrote:
mainhoon wrote:
How many of the 10 running times are more than one SD below the mean.

So then 1SD below the mean is 77.6. It asks how many of the 10 running times are more than 77.6? I just replaced the one SD below the mean by the value. There are more than 2... What am I missing?


You have a problem with wording.

WRONG reading:
How many of the 10 running times are more than one SD below the mean. So more than Mean-SD.

CORRECT reading:
How many of the 10 running times are more than one SD below the mean. So less than Mean-SD.


I am still not getting this..
Why is it less and not more..
Please elaborate ..


This is more verbal issue than math. In English the first reading is not correct while the second one is.
_________________

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

Kudos [?]: 136007 [0], given: 12723

1 KUDOS received
Director
Director
avatar
Status: Gonna rock this time!!!
Joined: 22 Jul 2012
Posts: 505

Kudos [?]: 72 [1], given: 562

Location: India
GMAT 1: 640 Q43 V34
GMAT 2: 630 Q47 V29
WE: Information Technology (Computer Software)
Re: 70 75 80 85 90 105 105 130 130 130 The list shown consist of [#permalink]

Show Tags

New post 04 Jan 2013, 08:13
1
This post received
KUDOS
Got it finally..
here: http://www.beatthegmat.com/beat-the-sta ... tml#548282
_________________

hope is a good thing, maybe the best of things. And no good thing ever dies.

Who says you need a 700 ?Check this out : http://gmatclub.com/forum/who-says-you-need-a-149706.html#p1201595

My GMAT Journey : http://gmatclub.com/forum/end-of-my-gmat-journey-149328.html#p1197992

Kudos [?]: 72 [1], given: 562

1 KUDOS received
Intern
Intern
avatar
Status: Preparing for GMAT
Joined: 10 Dec 2013
Posts: 18

Kudos [?]: 7 [1], given: 61

Location: India
Concentration: Marketing, Leadership
GMAT 1: 530 Q46 V18
WE: Other (Entertainment and Sports)
Re: 70 75 80 85 90 105 105 130 130 130 The list shown consist of [#permalink]

Show Tags

New post 14 Aug 2014, 11:11
1
This post received
KUDOS
How many of the 10 running times are more than one SD below the mean.?

This is a pretty mean and twisted question, especially on GMAT because only one out of ten would be able to crack it under 2 mins.
To understand this question, draw or visualize the standard deviation-mean graph. Look at it this way:
How many of the running times are farther than one standard deviation below the mean? Another way of looking at it is, how many values lie towards the left of one standard deviation below the mean.

This is what the graph looks like : https://www.google.co.in/url?sa=i&rct=j ... 9705195344

Hope it is clear.

Kudos [?]: 7 [1], given: 61

Intern
Intern
avatar
Joined: 03 May 2015
Posts: 19

Kudos [?]: [0], given: 34

Re: 70 75 80 85 90 105 105 130 130 130 The list shown consist of [#permalink]

Show Tags

New post 25 Jul 2015, 08:22
Btw, isn't the mean in the list above 97.5? (90+105/2)

Kudos [?]: [0], given: 34

Intern
Intern
avatar
Joined: 13 Sep 2015
Posts: 19

Kudos [?]: 10 [0], given: 239

Re: 70 75 80 85 90 105 105 130 130 130 The list shown consist of [#permalink]

Show Tags

New post 06 Oct 2015, 02:03
Long way:

find mean of the 10 numbers. mean is 100. Deduct 22.4 from 100, which equals 77.6. Only two values are below this number

Short way (not sure if this is always reliable):

You have to remember that in a normally distributed sample, Approx 16% of data points are more than 1 standard deviation from the mean, and 16% are less than 1 standard deviation from the mean (i.e. 64 % are within 1 S.d, and 32% are outside 1 S.d of the mean)

16% of the sample = 16/100 * 10 = 1.6 rounded off to 2.

Kudos [?]: 10 [0], given: 239

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 14782

Kudos [?]: 288 [0], given: 0

Premium Member
Re: 70 75 80 85 90 105 105 130 130 130 The list shown consist of [#permalink]

Show Tags

New post 17 Nov 2017, 23:45
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 288 [0], given: 0

Re: 70 75 80 85 90 105 105 130 130 130 The list shown consist of   [#permalink] 17 Nov 2017, 23:45

Go to page   Previous    1   2   [ 26 posts ] 

Display posts from previous: Sort by

70 75 80 85 90 105 105 130 130 130 The list shown consist of

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


GMAT Club MBA Forum Home| About| Terms and Conditions| 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®.