A set of data consists of the following 5 numbers: 0,2,4,6, : PS Archive
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 20 Jan 2017, 13:02

### 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

# A set of data consists of the following 5 numbers: 0,2,4,6,

Author Message
Director
Joined: 08 Jun 2007
Posts: 583
Followers: 2

Kudos [?]: 97 [0], given: 0

A set of data consists of the following 5 numbers: 0,2,4,6, [#permalink]

### Show Tags

26 Nov 2007, 20:09
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

A set of data consists of the following 5 numbers: 0,2,4,6, and 8. Which two numbers, if added to create a set of 7 numbers, will result in a new standard deviation that is close to the standard deviation for the original 5 numbers?

A) -1 and 9
B) 4 and 4
C) 3 and 5
D) 2 and 6
E) 0 and 8

I know the solution but I just didn't like . Looking for nice and easy approach or link if this was posted earlier.
CEO
Joined: 17 Nov 2007
Posts: 3589
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 548

Kudos [?]: 3559 [0], given: 360

### Show Tags

26 Nov 2007, 21:40
D.

av=(0+2+4+6+8)/5=4

remember that d=(x-xav)^2 is a key part of standard deviation.

d e {16,4,0,4,16} sd^2=40/5=8

A) -1 and 9 - d=25;25 is too large.
B) 4 and 4 - d=0;0 is too small.
C) 3 and 5 - d=1;1 is too small.
D) 2 and 6 - d=4;4 is possible. sd^2=48/7~7 - the closest.
E) 0 and 8 - d=16;16 is possible. sd^2=72/7~10

Maybe the solution is not so easy. what's OA?
SVP
Joined: 29 Aug 2007
Posts: 2492
Followers: 67

Kudos [?]: 734 [0], given: 19

### Show Tags

26 Nov 2007, 22:21
walker wrote:
D.

av=(0+2+4+6+8)/5=4

remember that d=(x-xav)^2 is a key part of standard deviation.

d e {16,4,0,4,16} sd^2=40/5=8

A) -1 and 9 - d=25;25 is too large.
B) 4 and 4 - d=0;0 is too small.
C) 3 and 5 - d=1;1 is too small.
D) 2 and 6 - d=4;4 is possible. sd^2=48/7~7 - the closest.
E) 0 and 8 - d=16;16 is possible. sd^2=72/7~10

Maybe the solution is not so easy. what's OA?

depends how you divide the sum of square dev.

if by n, then E.
if by (n-1), then D.

not sure whaat we use in gmat. imo, for small samples (less than 30), we should use (n-1). so D.
CEO
Joined: 17 Nov 2007
Posts: 3589
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 548

Kudos [?]: 3559 [0], given: 360

### Show Tags

26 Nov 2007, 22:53
GMAT TIGER wrote:
depends how you divide the sum of square dev.

You are absolutely right. I know that but n is the case of GMAT. I've refreshed my knowledge about standard deviation just before put solution.
(p.115-116 in OG 11th edition.)
......
The other difference of "GMAT logic" from normal one is ignoring densities of materials in solution/mixture problems....
CEO
Joined: 17 Nov 2007
Posts: 3589
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 548

Kudos [?]: 3559 [0], given: 360

### Show Tags

26 Nov 2007, 22:58
GMAT TIGER wrote:
if by n, then E.
if by (n-1), then D.

rather

if by n, then D.
if by (n-1), then E.

sd^2=40/4=10

4) 48/6=8

5) 72/6=12 - the closest.
Director
Joined: 09 Aug 2006
Posts: 763
Followers: 1

Kudos [?]: 192 [0], given: 0

Re: PS - Standard Deviation [#permalink]

### Show Tags

26 Nov 2007, 23:13
ashkrs wrote:
A set of data consists of the following 5 numbers: 0,2,4,6, and 8. Which two numbers, if added to create a set of 7 numbers, will result in a new standard deviation that is close to the standard deviation for the original 5 numbers?

A) -1 and 9
B) 4 and 4
C) 3 and 5
D) 2 and 6
E) 0 and 8

I know the solution but I just didn't like . Looking for nice and easy approach or link if this was posted earlier.

You can calculate the variance for the original set and then the variance for the new set to determine that D is the answer.

However, how do you solve this without calculating the variance?
Re: PS - Standard Deviation   [#permalink] 26 Nov 2007, 23:13
Display posts from previous: Sort by