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

 It is currently 26 Oct 2016, 06:27

### 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

# Standard deviation question?

Author Message
TAGS:

### Hide Tags

Director
Joined: 29 Nov 2012
Posts: 900
Followers: 14

Kudos [?]: 951 [0], given: 543

### Show Tags

17 Jan 2013, 00:42
I know this isn't very common on the gmat but can this approach be used to calculate S.D?

Example 1,3,5

Mean 9/3 = 3

subtract difference from each term so -2,0,2

square each term 4,0,4

divide the above sum by number of terms 8/3

S.d = square root of the sum = square root of 8/3?

is this approach correct?
_________________

Click +1 Kudos if my post helped...

Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/

GMAT Prep software What if scenarios http://gmatclub.com/forum/gmat-prep-software-analysis-and-what-if-scenarios-146146.html

Director
Status: Done with formalities.. and back..
Joined: 15 Sep 2012
Posts: 647
Location: India
Concentration: Strategy, General Management
Schools: Olin - Wash U - Class of 2015
WE: Information Technology (Computer Software)
Followers: 44

Kudos [?]: 521 [1] , given: 23

### Show Tags

17 Jan 2013, 01:21
1
KUDOS
fozzzy wrote:
I know this isn't very common on the gmat but can this approach be used to calculate S.D?

Example 1,3,5

Mean 9/3 = 3

subtract difference from each term so -2,0,2

square each term 4,0,4

divide the above sum by number of terms 8/3

S.d = square root of the sum = square root of 8/3?

is this approach correct?

Yes. But if a question on GMAT asks u to calculate SD using this approach, pat yourself on the back for you would've crossed Q52
_________________

Lets Kudos!!!
Black Friday Debrief

Senior Manager
Joined: 02 Sep 2012
Posts: 259
Location: United States
Concentration: Entrepreneurship, Finance
GMAT Date: 07-25-2013
GPA: 3.83
WE: Architecture (Computer Hardware)
Followers: 5

Kudos [?]: 171 [0], given: 99

### Show Tags

17 Jan 2013, 01:26
Normally GMAT gives you two sets and asks you to compare between the two sets which has the highest S.D value.
_________________

"Giving kudos" is a decent way to say "Thanks" and motivate contributors. Please use them, it won't cost you anything

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 6971
Location: Pune, India
Followers: 2031

Kudos [?]: 12771 [0], given: 221

### Show Tags

19 Jan 2013, 00:28
fozzzy wrote:
I know this isn't very common on the gmat but can this approach be used to calculate S.D?

Example 1,3,5

Mean 9/3 = 3

subtract difference from each term so -2,0,2

square each term 4,0,4

divide the above sum by number of terms 8/3

S.d = square root of the sum = square root of 8/3?

is this approach correct?

$$SD = \sqrt{Sum(Ai - Aavg)^2/n}$$
Ai represents the terms from 1 to n.
Aavg is the average of all the terms.
n is the number of terms.

Basically, you are using this formula.

The process is tedious so it is not asked on GMAT. All you need to know is how to compare SDs of two sets and how a change in a set affects the SD.
Check out this post:
http://www.veritasprep.com/blog/2012/06 ... deviation/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for \$199

Veritas Prep Reviews

Current Student
Joined: 27 Jun 2012
Posts: 418
Concentration: Strategy, Finance
Followers: 75

Kudos [?]: 741 [1] , given: 184

### Show Tags

19 Jan 2013, 13:14
1
KUDOS
Your method of calculating SD is correct. This link also gives good details on SD concepts.
http://www.platinumgmat.com/gmat_study_ ... _deviation

Below questions are a MUST SOLVE to get your hands on SD:
_________________

Thanks,
Prashant Ponde

Tough 700+ Level RCs: Passage1 | Passage2 | Passage3 | Passage4 | Passage5 | Passage6 | Passage7
VOTE GMAT Practice Tests: Vote Here
PowerScore CR Bible - Official Guide 13 Questions Set Mapped: Click here

Director
Affiliations: GMATQuantum
Joined: 19 Apr 2009
Posts: 583
Followers: 112

Kudos [?]: 418 [0], given: 14

### Show Tags

21 Jan 2013, 19:51
GMAT does ask you to compute the standard deviation of a finite set, however they will provide you with an expression that will tell you how to compute the standard deviation. You will just need to interpret the different terms in the expression for the standard deviation. For example, they will give you an explicit formula for the standard deviation and in the description they may say things like m is the mean of the numbers in the set and n is the number of terms in the list, etc. So technically you don't have to know the formula for the standard deviation, but they do expect you to interpret the expression for standard deviation. I would classify this type of a question as medium, partly because a lot of students will be thrown off by the tedious looking expression for standard deviation.

Now, I also do want to point out that you may also be asked to recognize that the standard deviation is related to the sum of the square of the deviations from the mean in a data sufficiency context, however this question would likely fall in the Q51 range.

Cheers,
Dabral
Re: Standard deviation question?   [#permalink] 21 Jan 2013, 19:51
Similar topics Replies Last post
Similar
Topics:
6 How to Quickly Solve Standard Deviation Questions on the GMAT 1 25 Mar 2015, 04:50
PS Standard Deviation question 0 16 Mar 2015, 08:33
Standard Deviation List question 1 30 Jun 2013, 09:37
Question about Standard Deviation 2 01 Nov 2010, 22:18
10 Questions about the standard deviation 18 01 Apr 2010, 23:19
Display posts from previous: Sort by