Find all School-related info fast with the new School-Specific MBA Forum

It is currently 22 Oct 2014, 08:16

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A vending machine is designed to dispense 8 oz. of coffee

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 02 Jul 2007
Posts: 112
Followers: 1

Kudos [?]: 1 [0], given: 0

A vending machine is designed to dispense 8 oz. of coffee [#permalink] New post 31 Aug 2007, 17:01
A vending machine is designed to dispense 8 oz. of coffee intto a cup. After a test that recorded the number of oz. of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in oz., were selected from the data. If the 1,000 recorded amounts have a mean of 8.1 oz. and a standard deviation of 0.3 oz., how many of the 12 listed amounted are within 1.5 standard deviations of the mean?

7.51 8.22 7.86 8.36
8.09 7.83 8.30 8.01
7.73 8.25 7.96 8.53
Director
Director
avatar
Joined: 22 Aug 2007
Posts: 573
Followers: 1

Kudos [?]: 13 [0], given: 0

Re: Gmatprep; standard deviation [#permalink] New post 31 Aug 2007, 17:28
gnr646 wrote:
A vending machine is designed to dispense 8 oz. of coffee intto a cup. After a test that recorded the number of oz. of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in oz., were selected from the data. If the 1,000 recorded amounts have a mean of 8.1 oz. and a standard deviation of 0.3 oz., how many of the 12 listed amounted are within 1.5 standard deviations of the mean?

7.51 8.22 7.86 8.36
8.09 7.83 8.30 8.01
7.73 8.25 7.96 8.53


Do they ask these questions on GMAT?
:shock:
Manager
Manager
avatar
Joined: 02 Jul 2007
Posts: 112
Followers: 1

Kudos [?]: 1 [0], given: 0

 [#permalink] New post 31 Aug 2007, 17:36
Yah, I was floored. This one came in the first GMATprep I took a couple of weeks ago. Needless to say, I completely guessed and moved on. No way was I answering that in under 2 min. Anyone have good shortcuts for stats questions like this?
Manager
Manager
avatar
Joined: 20 Dec 2004
Posts: 181
Followers: 2

Kudos [?]: 13 [0], given: 0

 [#permalink] New post 31 Aug 2007, 18:19
mean=8.1 SD=0.3 Therefore 1.5SD=0.45

Hence all values that fall under 8.1-0.45 to 8.1+0.45 is within 1.5 SD from the mean.

i.e we should look out for values between 7.65 and 8.55

There are 11 such values.
_________________

Regards

Subhen

Director
Director
avatar
Joined: 22 Aug 2007
Posts: 573
Followers: 1

Kudos [?]: 13 [0], given: 0

 [#permalink] New post 31 Aug 2007, 19:06
subhen wrote:
mean=8.1 SD=0.3 Therefore 1.5SD=0.45

Hence all values that fall under 8.1-0.45 to 8.1+0.45 is within 1.5 SD from the mean.

i.e we should look out for values between 7.65 and 8.55

There are 11 such values.


Please, can you post the formula or formulas according to which you derived text in bold...

thanks
Director
Director
avatar
Joined: 11 Jun 2007
Posts: 932
Followers: 1

Kudos [?]: 51 [0], given: 0

 [#permalink] New post 31 Aug 2007, 19:38
IrinaOK wrote:
subhen wrote:
mean=8.1 SD=0.3 Therefore 1.5SD=0.45

Hence all values that fall under 8.1-0.45 to 8.1+0.45 is within 1.5 SD from the mean.

i.e we should look out for values between 7.65 and 8.55

There are 11 such values.


Please, can you post the formula or formulas according to which you derived text in bold...

thanks


the question states that the SD = 0.3, and asks how many of the 12 listed amounts are 1.5 within the SD, so it is SD * 1.5 = 0.3 * 1.5 = 0.45. There is no tricky formula involved. From there we find the values that would be within 0.45 from the mean/average of 8.1. This range as explained above is between 7.65 and 8.55 (+/- 0.45). Hence from the list, we see that there are 11 out of 12 amounts.
Director
Director
avatar
Joined: 22 Aug 2007
Posts: 573
Followers: 1

Kudos [?]: 13 [0], given: 0

 [#permalink] New post 01 Sep 2007, 07:06
beckee529 wrote:
IrinaOK wrote:
subhen wrote:
mean=8.1 SD=0.3 Therefore 1.5SD=0.45

Hence all values that fall under 8.1-0.45 to 8.1+0.45 is within 1.5 SD from the mean.

i.e we should look out for values between 7.65 and 8.55

There are 11 such values.


Please, can you post the formula or formulas according to which you derived text in bold...

thanks



the question states that the SD = 0.3, and asks how many of the 12 listed amounts are 1.5 within the SD, so it is SD * 1.5 = 0.3 * 1.5 = 0.45. There is no tricky formula involved. From there we find the values that would be within 0.45 from the mean/average of 8.1. This range as explained above is between 7.65 and 8.55 (+/- 0.45). Hence from the list, we see that there are 11 out of 12 amounts.


got it,

actually, it is wording and redundant numbers that make it look complex...

Thank you for explanation!

Still wonder what OA is.

gnr646, can you please post it?
Manager
Manager
avatar
Joined: 02 Jul 2007
Posts: 112
Followers: 1

Kudos [?]: 1 [0], given: 0

 [#permalink] New post 01 Sep 2007, 09:45
sorry, OA is was 11. I did the same thing - got tripped up in the wording.
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 07 Jul 2004
Posts: 5095
Location: Singapore
Followers: 19

Kudos [?]: 155 [0], given: 0

 [#permalink] New post 02 Sep 2007, 22:04
Nothing tricky about this.

Mean is given -> 8.1
S.D is given -> 0.3

1.5S.D = +/- 0.45 from mean -> so we need values between 7.65 and 8.55. There are 11 such values.

Even if you missed it, you can work out a range and pick from the choices given. 1 S.D is about 64.8% of the number of values, which works out to ~8 values are within 1 S.D. 2S.D is about 95.4% of the number of values which works out to ~slight above 11 of the values are within 2S.D. So you should be picking an answer between 8-11. Tough luck if your choices are 8,9,10,11 though....
CEO
CEO
User avatar
Joined: 29 Mar 2007
Posts: 2593
Followers: 16

Kudos [?]: 197 [0], given: 0

Re: Gmatprep; standard deviation [#permalink] New post 02 Sep 2007, 22:20
gnr646 wrote:
A vending machine is designed to dispense 8 oz. of coffee intto a cup. After a test that recorded the number of oz. of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in oz., were selected from the data. If the 1,000 recorded amounts have a mean of 8.1 oz. and a standard deviation of 0.3 oz., how many of the 12 listed amounted are within 1.5 standard deviations of the mean?

7.51 8.22 7.86 8.36
8.09 7.83 8.30 8.01
7.73 8.25 7.96 8.53


ughh this question lol. Its so easy, but b/c of time pressure on my GMATPrep, I got it wrong. Entered the wrong choice :evil: neway if u don't know SD well, its pretty easy to learn.

mean is 8.1 So just add 1.5(.03)=.45 to 8.1 and subtract .45 from 8.1. You get 7.65-8.55 So just find the numbers that fall inbetween these two numbers. Ans is 11.
Re: Gmatprep; standard deviation   [#permalink] 02 Sep 2007, 22:20
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic Jamal can fill the vending machine in 45 minutes. When his EugeneZelenyi 2 19 Mar 2012, 10:38
20 Experts publish their posts in the topic A vending machine is designed to dispense 8 ounces of coffee zz0vlb 9 27 Apr 2010, 05:21
2 Experts publish their posts in the topic A vending machine randomly dispenses four different types of prasannar 12 21 Mar 2008, 22:18
A vending machine is designed to dispense 8 ouces of coffee Matrix02 6 27 Nov 2006, 17:13
A vending machine is designed to dispense 8 ounces of coffee alimad 1 25 Sep 2006, 21:39
Display posts from previous: Sort by

A vending machine is designed to dispense 8 oz. of coffee

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.