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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A set of data consists of the following 5 numbers: 0,2,4,6, [#permalink]
26 Nov 2007, 20:09

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

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

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.

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

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.

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....

Re: PS - Standard Deviation [#permalink]
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?

gmatclubot

Re: PS - Standard Deviation
[#permalink]
26 Nov 2007, 23:13

Type of Visa: You will be applying for a Non-Immigrant F-1 (Student) US Visa. Applying for a Visa: Create an account on: https://cgifederal.secure.force.com/?language=Englishcountry=India Complete...

I started running back in 2005. I finally conquered what seemed impossible. Not sure when I would be able to do full marathon, but this will do for now...