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

 It is currently 03 May 2015, 10:30

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If a certain sample od data has mean of 20.0 and a standard

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Intern
Joined: 06 Sep 2003
Posts: 19
Location: island
Followers: 0

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

If a certain sample od data has mean of 20.0 and a standard [#permalink]  08 Sep 2003, 09:06
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
If a certain sample od data has mean of 20.0 and a standard deviation of 3.0, which of the following values id more than 2.5 standard deviations from the means?
a)12.0 b)13.5 c)17.0 d)23.5 e)26.5

The answer is (a)

I don't understand the explanation in the book.
Who can help me?
CEO
Joined: 15 Aug 2003
Posts: 3469
Followers: 61

Kudos [?]: 702 [0], given: 781

Re: PS [#permalink]  08 Sep 2003, 09:57
mystery wrote:
If a certain sample od data has mean of 20.0 and a standard deviation of 3.0, which of the following values id more than 2.5 standard deviations from the means?
a)12.0 b)13.5 c)17.0 d)23.5 e)26.5

The answer is (a)

I don't understand the explanation in the book.
Who can help me?

20 - 2.5*3 = 12.5

20 + 2.5*3 = 27.5

find the number which is lesser than 12.5 OR greater than 27.5

i guess theres only one...12

thanks
praetorian
Intern
Joined: 06 Sep 2003
Posts: 19
Location: island
Followers: 0

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

[#permalink]  08 Sep 2003, 16:27
Why do we use these equation?

20 +3*2.5=12.5
20 -3*2.5=27.5

I don't know the reasons.

Thanks!!
CEO
Joined: 15 Aug 2003
Posts: 3469
Followers: 61

Kudos [?]: 702 [1] , given: 781

[#permalink]  08 Sep 2003, 16:58
1
KUDOS
mystery wrote:
Why do we use these equation?

20 +3*2.5=12.5
20 -3*2.5=27.5

I don't know the reasons.

Thanks!!

oh.. i am sorry...

We use statistical measures to draw conclusion about a sample on which data has been collected..
For example, you may collect data on the height of the students in 5th grade. If you want to report it statistically, the most common way is to report the mean and the standard deviation...

Mean (Average) is the average of the heights in our sample...
to give more information, we provide the standard deviation..

The standard deviation[SD] tells you how much variation is there is the data..For example , we may find that the S.D for the data is0.4 feet. The 0.4 feet is the deviation about the mean
let the mean be 5 feet.

now , if we are asked...what is the value of heights that are 2 standard deviations from the mean ?

we know SD = 0.4
so 2 SD = 2* 0.4 = 0.8

Now deviation is both to the left and the right of the mean

To the left, we subtract 0.8 from 5 and get one value...which is 4.2
and To the right, we add 0.8 to 5 and get 5.8

These values of 4.2 and 5.8 represent the values that lie TWO SD's from the mean....

Please reply back if you didnt understand...
Hope my explanation was useful..

i tried to draw a diagram ,but it didnt come out right in the post..so i deleted it avoid confusion.

Thanks
Praetorian
Intern
Joined: 06 Sep 2003
Posts: 19
Location: island
Followers: 0

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

[#permalink]  09 Sep 2003, 05:58
Praetorian,

Thanks very much, your explanation is very clear.

Thanks a lot!!

Mystery
[#permalink] 09 Sep 2003, 05:58
Similar topics Replies Last post
Similar
Topics:
2 If a certain sample of data has a mean of 24.0 and the value 5 28 May 2014, 09:05
6 If a certain sample of data has a mean of 20.0 and a 7 11 Apr 2012, 00:46
5 If a certain sample of data has a mean of 20.0 and a 7 19 Feb 2012, 15:04
If a certain sample of data has a mean of 20.0 1 03 Feb 2011, 15:06
If a certain sample of data has a mean of 20 and a standard 5 17 Oct 2008, 10:27
Display posts from previous: Sort by

# If a certain sample od data has mean of 20.0 and a standard

 Question banks Downloads My Bookmarks Reviews Important topics

 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®.