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:

You make a new sequence by removing 2 elements from the [#permalink]
24 Nov 2005, 04:38

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

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

You make a new sequence by removing 2 elements from the sequence {1, 3, 5, 7, 9, 11, 13, 15, 17, 19}. What is the standard deviation of the new sequence?

(1) The median of the new sequence is 10.
(2) The new sequence has the same average as the original sequence. _________________

Re: DS - Standard deviation [#permalink]
24 Nov 2005, 07:22

E.

from i, sequuences {1, 3, 5, 7, 13, 15, 17, 19} and {3, 5, 7, 9, 11, 13, 15, 17}, both, have median 10 but they have different SDs.

from ii, sequuences {1, 3, 5, 7, 13, 15, 17, 19} and {3, 5, 7, 9, 11, 13, 15, 17}, both, have the same mean 10 as the original has but their SDs are different.

from i and ii also the have different SDs with same mean and median.

Re: DS - Standard deviation [#permalink]
24 Nov 2005, 23:42

HIMALAYA wrote:

E.

from i, sequuences {1, 3, 5, 7, 13, 15, 17, 19} and {3, 5, 7, 9, 11, 13, 15, 17}, both, have median 10 but they have different SDs.

from ii, sequuences {1, 3, 5, 7, 13, 15, 17, 19} and {3, 5, 7, 9, 11, 13, 15, 17}, both, have the same mean 10 as the original has but their SDs are different.

from i and ii also the have different SDs with same mean and median.

HIMALAYA...
can you pls explain ..how you concluded that these different sets will have different SD.. .....any trick or just observation ...

Re: DS - Standard deviation [#permalink]
10 Jun 2006, 19:35

gamjatang wrote:

You make a new sequence by removing 2 elements from the sequence {1, 3, 5, 7, 9, 11, 13, 15, 17, 19}. What is the standard deviation of the new sequence?

(1) The median of the new sequence is 10. (2) The new sequence has the same average as the original sequence.

Pick E in this one.
(1) in order to maintain the median of 10, we have several cases:
Keep (9,11) , we can remove any number of the rest : one number in the left side of (9,11) and another in the right side of (9,11).
For example: remove 1 and 19 ...then compare with removal of (3,19). The two standard deviations are different ---> that means we can't have exactly the same SD for all removals ---> can't find such SD --> insuff

(2) this statement means: the two removed numbers have a sum which is equal to mean*2 . The mean here is 10 . Thus, the pairs of removal can be either ( 1,19) , (3,17) , (5,15) , (3,13) , (9,11) . Since the mean is unchanged, the removal of (1,19) yields a smaller SD than that of (3,13) because (1,19) has wider distances to the mean than (3,13) does. --> no common SD for all removal --> insuff

gmatclubot

Re: DS - Standard deviation
[#permalink]
10 Jun 2006, 19:35

Hello everyone! Researching, networking, and understanding the “feel” for a school are all part of the essential journey to a top MBA. Wouldn’t it be great... ...

As part of our focus on MBA applications next week, which includes a live QA for readers on Thursday with admissions expert Chioma Isiadinso, we asked our bloggers to...

Booth allows you flexibility to communicate in whatever way you see fit. That means you can write yet another boring admissions essay or get creative and submit a poem...