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.

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:

The lifetime of all the batteries produced by a certain comp [#permalink]
21 Sep 2010, 20:34

4

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

25% (medium)

Question Stats:

71% (01:45) correct
29% (00:48) wrong based on 151 sessions

The lifetime of all the batteries produced by a certain company in a year have a distribution that is symmetric about the mean m. If the distribution has a standard deviation of d, what percent of the distribution is greater than m+d?

(1) 68 percent of the distribution lies in the interval from m-d to m+d, inclusive (2) 16 percent of the distribution is less than m-d

Can sum1 explain the concept behind this...Looking at the answer I have come up with my own assumptions...

Re: SD symmetric about the mean [#permalink]
21 Sep 2010, 20:59

4

This post received KUDOS

Expert's post

1

This post was BOOKMARKED

The lifetime of all the batteries produced by a certain company in a year have a distribution that is symmetric about the mean m. If the distribution has a standard deviation of d, what percent of the distribution is greater than m+d?

Symmetric about the mean means that the shape of the distribution on the right and left side of the curve are mirror-images of each other.

(1) 68% of the distribution lies in the interval from m-d to m+d, inclusive --> 100%-68%=32% is less than m-d and more than m+d. As distribution is symmetric about the mean then exactly half of 32%, or 16%, would be more than m+d. Sufficient.

(2) 16% of the distribution is less than m-d --> again, as distribution is symmetric about the mean then exactly 16%, will be more than m+d. Sufficient.

Re: SD symmetric about the mean [#permalink]
22 Sep 2010, 15:34

Thank you. I drew a diagram with normal distribution and came up with this assumptions...But now I am happy looking at ur explanations that my assumptions are true. +1 _________________

Re: SD symmetric about the mean [#permalink]
15 Mar 2011, 23:31

Bunuel wrote:

The lifetime of all the batteries produced by certain companies have a distribution which is symmetric about mean m. If the distribution has a standard deviation of d , what percentage of distribution is greater than m+d?

Symmetric about the mean means that the shape of the distribution on the right and left side of the curve are mirror-images of each other.

(1) 68% of the distribution lies in the interval from m-d to m+d, inclusive --> 100%-68%=32% is less than m-d and more than m+d. As distribution is symmetric about the mean then exactly half of 32%, or 16%, would be more than m+d. Sufficient.

(2) 16% of the distribution is less than m-d --> again, as distribution is symmetric about the mean then exactly 16%, will be more than m+d. Sufficient.

Answer: D.

Hope it helps.

OMG You make all these horible definitions easier to breathe. i used to be of much fear when thinking of DS but when looking some explanations here, i feel the world is not so dark _________________

Consider giving me kudos if you find my explanations helpful so i can learn how to express ideas to people more understandable.

Status: Manager, Indian Petroleum PSU (Rag picking to Signing Deals) 1 yr Consulting, 6 yrs in Oil&Gas and now Immortal Beggar for 700 above | My Hope: Non IT, Non Banking Indian male in Energy Sector|

Re: SD symmetric about the mean [#permalink]
02 Feb 2012, 09:09

@ ghosh

bell curve is an important topic and often questions crop up. i got one such in my gmat, though it was east, but the qs stem is verbose and one has to make out that its a qs on bell curve. _________________

"To be Nobody but yourself in a world that's doing its best to make you somebody else, is to fight the hardest battle you are ever going to fight. never stop fighting" - E.E Cummings

It's not about the decisions u take, it's about the ones u don't. Period. - Anon

Mind is everything, u become what u think - Gautam Buddha

He who is not courageous enough to take risks will accomplish nothing in life - Muhammad Ali

Re: SD symmetric about the mean [#permalink]
02 Jul 2013, 05:57

Bunuel wrote:

The lifetime of all the batteries produced by a certain company in a year have a distribution that is symmetric about the mean m. If the distribution has a standard deviation of d, what percent of the distribution is greater than m+d?

Symmetric about the mean means that the shape of the distribution on the right and left side of the curve are mirror-images of each other.

(1) 68% of the distribution lies in the interval from m-d to m+d, inclusive --> 100%-68%=32% is less than m-d and more than m+d. As distribution is symmetric about the mean then exactly half of 32%, or 16%, would be more than m+d. Sufficient.

(2) 16% of the distribution is less than m-d --> again, as distribution is symmetric about the mean then exactly 16%, will be more than m+d. Sufficient.

Answer: D.

Hope it helps.

How valuable is the portion in red if you don't read the question carefully would have marked C instead of D! _________________

Re: The lifetime of all the batteries produced by a certain comp [#permalink]
04 Sep 2014, 10:39

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

I couldn’t help myself but stay impressed. young leader who can now basically speak Chinese and handle things alone (I’m Korean Canadian by the way, so...