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

 It is currently 22 May 2015, 10:27

### 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

# M11 q28

Author Message
Manager
Joined: 13 May 2010
Posts: 125
Followers: 0

Kudos [?]: 8 [0], given: 4

M11 q28 [#permalink]  30 Jan 2012, 08:56
Is the standard deviation of set $$S$$ greater than the standard deviation of set $$T$$ ?

1. The range of set $$S$$ is greater than the range of set $$T$$
2. The mean of set $$S$$ is greater than the mean of set $$T$$

OA: (E)

Can someone please explain me this one?
Chat Moderator
Joined: 31 Oct 2011
Posts: 521
Schools: Johnson '16 (M)
GMAT 1: 690 Q45 V40
WE: Asset Management (Mutual Funds and Brokerage)
Followers: 36

Kudos [?]: 204 [0], given: 57

Re: M11 q28 [#permalink]  30 Jan 2012, 09:02
teal wrote:
Is the standard deviation of set $$S$$ greater than the standard deviation of set $$T$$ ?

1. The range of set $$S$$ is greater than the range of set $$T$$
2. The mean of set $$S$$ is greater than the mean of set $$T$$

OA: (E)

Can someone please explain me this one?

Where did you get tripped up?

Quite simply,
1: No information about the Mean or number of terms, hence insufficient.

2: No information about the number of terms, hence insufficient.

The question you're asking yourself is "do the data points in set S deviate further from the mean of set S than the data points in set T deviate from their mean?"
_________________

My Applicant Blog: http://hamm0.wordpress.com/

Math Expert
Joined: 02 Sep 2009
Posts: 27465
Followers: 4305

Kudos [?]: 42102 [0], given: 5956

Re: M11 q28 [#permalink]  30 Jan 2012, 13:01
Expert's post
teal wrote:
Is the standard deviation of set $$S$$ greater than the standard deviation of set $$T$$ ?

1. The range of set $$S$$ is greater than the range of set $$T$$
2. The mean of set $$S$$ is greater than the mean of set $$T$$

OA: (E)

Can someone please explain me this one?

For the GMAT you only need to understand the concept of SD: you won't be asked to actually calculate the standard deviation of a set on the GMAT. So, what is the main thing you should know about it? Standard deviation shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values.

Now, (1) says that the range of S is greater than the range of T, so the biggest and smallest numbers in S are more widespread than the biggest and smallest numbers in T. But what about the other numbers of these sets?

SD of {0, 10} is greater than SD of {0, 9}, but SD of {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10} is less than SD of {0, 9}. Not sufficient.

(2) The mean of set S is greater than the mean of set T. Info about the mean is totally useless to get how widespread the given sets are. Not sufficient.

(1)+(2) Statement (2) gives absolutely no new info for (1), so even taken together they are still insufficient to answer the question.

Check this for more: math-standard-deviation-87905.html

Hope it helps.
_________________
Manager
Joined: 13 May 2010
Posts: 125
Followers: 0

Kudos [?]: 8 [0], given: 4

Re: M11 q28 [#permalink]  30 Jan 2012, 13:50
Thanks a lot Bunuel and hammo!

Bunuel - thanks for providing all the info.
Manager
Joined: 13 May 2010
Posts: 125
Followers: 0

Kudos [?]: 8 [0], given: 4

Re: M11 q28 [#permalink]  31 Jan 2012, 18:24
SD of {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10} is less than SD of {0, 5}

How did you reach that conclusion? Isn' the std dev. higher for the first set?
What is the best way ( most efficient) to compare the std dev. of given sets without calculating the actual std. dev. ( MGMAT guide covers this topic a little bit)?
Math Expert
Joined: 02 Sep 2009
Posts: 27465
Followers: 4305

Kudos [?]: 42102 [0], given: 5956

Re: M11 q28 [#permalink]  31 Jan 2012, 19:09
Expert's post
teal wrote:
SD of {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10} is less than SD of {0, 5}

How did you reach that conclusion? Isn' the std dev. higher for the first set?
What is the best way ( most efficient) to compare the std dev. of given sets without calculating the actual std. dev. ( MGMAT guide covers this topic a little bit)?

It should be SD of {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10} is less than SD of {0, 9}. Anyway the given sets are just examples to demonstrate the point. Follow the links in my previous post for the staff you need to know about SD. The GMAT SD questions are pretty straightforward and to answer them you just need to understand its concept.
_________________
Re: M11 q28   [#permalink] 31 Jan 2012, 19:09
Similar topics Replies Last post
Similar
Topics:
m08 Q28 4 16 Apr 2011, 05:10
7 m14 q28 20 05 Jan 2010, 21:39
m11,#8 13 11 Nov 2008, 22:35
20 m11#9 9 01 Nov 2008, 07:23
2 M11 #03 2 01 Oct 2008, 14:20
Display posts from previous: Sort by

# M11 q28

Moderators: Bunuel, WoundedTiger

 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®.