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 500,000 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:

Is the standard deviation of ages of students in class A [#permalink]

Show Tags

18 Feb 2004, 09:50

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct
100% (01:32) wrong based on 2 sessions

HideShow timer Statistics

Class..............Average Age........# of Students A..................15 years.....................6 B..................16 years.....................12

Is the standard deviation of ages of students in class A greater than the standard deviation of the ages of students in class B?

(1) The maximum difference between the ages of any two students in class A is 1 year.

(2) No student in class B is more than 6 months older than any other student.

C would be the answer
From 1) St. dev. for A is 1 yr. not suff. since we don't know the st. dev. of B
From 2) st. dev. for B is 1/2 yr. not suff. since we don't know the st. dev. of A

Both together we know their relative st. dev. and thus conclude that B's st. dev. is less. St. dev. is a measure of dispersion from the mean. Therefore, the averages of 15 for A and 16 for B have no incidence in selecting an answer regarding st. dev.
_________________

In S1 and S2, we are given the age difference b/w any two students. Is it mean Std Deviation? I think it is Range rather than Std Dev.

Please clarify ans also give some more explanations.
_________________

Want to improve your CR: http://gmatclub.com/forum/cr-methods-an-approach-to-find-the-best-answers-93146.html Tricky Quant problems: http://gmatclub.com/forum/50-tricky-questions-92834.html Important Grammer Fundamentals: http://gmatclub.com/forum/key-fundamentals-of-grammer-our-crucial-learnings-on-sc-93659.html

Standard deviation indicates the spread of data points around the mean. So the stem is asking whether the points in data set A cluster further away from the mean (on average) than the points in data set B.

Looking at the statements:

1) tells us that 1 is the maximum difference between the ages of any two students. This means that some students may be under 15, and some over 15, but since we need a final average that is exactly 15 years, the ages "under" will have to balance the ages "over. For example, you could have 3 students at 14.5 and 3 students at 15.5. But you could also have all students at exactly 15, which yields a st. dev. of 0.

2) is the same as 1, but with a range of 6 months max. Again, it could be 6 students at 3 months under 16, and 6 students at 3 months over 16. In this case, st. dev is > 0. But again, all ages could be exactly 16.

Since there is no information about the actual spread in either statement, and we only know that the range does not exceed a certain amount, the ans is E.

Standard deviation indicates the spread of data points around the mean. So the stem is asking whether the points in data set A cluster further away from the mean (on average) than the points in data set B.

Looking at the statements:

1) tells us that 1 is the maximum difference between the ages of any two students. This means that some students may be under 15, and some over 15, but since we need a final average that is exactly 15 years, the ages "under" will have to balance the ages "over. For example, you could have 3 students at 14.5 and 3 students at 15.5. But you could also have all students at exactly 15, which yields a st. dev. of 0.

2) is the same as 1, but with a range of 6 months max. Again, it could be 6 students at 3 months under 16, and 6 students at 3 months over 16. In this case, st. dev is > 0. But again, all ages could be exactly 16.

Since there is no information about the actual spread in either statement, and we only know that the range does not exceed a certain amount, the ans is E.

Good point mate .. I missed while reading the question and answered C but after readin your explanation I understand why should be E

Cheers

gmatclubot

Re: DS - Standard Deviation
[#permalink]
06 May 2010, 06:10

After days of waiting, sharing the tension with other applicants in forums, coming up with different theories about invites patterns, and, overall, refreshing my inbox every five minutes to...

I was totally freaking out. Apparently, most of the HBS invites were already sent and I didn’t get one. However, there are still some to come out on...

In early 2012, when I was working as a biomedical researcher at the National Institutes of Health , I decided that I wanted to get an MBA and make the...