Standard deviation DS:

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\'manpreet singh: Master | Next Rank: 500 Posts; Posts: 271; Joined: Tue May 22, 2012 3:22 amFollowed by: 3 members; Thanked: 7 times

by \'manpreet singh » Mon Aug 26, 2013 8:23 pm

Given that the mean of Set A is 10, what is the range of two standard deviations above and below the mean?

(1) One standard deviation above and below the mean ranges from 7 to 13.

(2) The median of set A is 11.

ans a

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Source: Beat The GMAT — Data Sufficiency | Mon Aug 26, 2013 8:23 pm

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by [email protected] » Mon Aug 26, 2013 9:47 pm

Hi manpreet,

Do you have a specific question or issue with this DS question?

On the GMAT, standard deviation is about how "spread out" a group of numbers is, relative to the mean/average. Here, we're asked what would be two standard deviations around a mean of 10.

Fact 1 tells us what 1 standard deviation would be in either direction (from 10 to 7 and from 10 to 13). This tells us that the SD = 3, so we can figure out what 2 SDs would be.
Fact 1 is SUFFICIENT

Fact 2 tells us the median, but doesn't give us any info about how spread out the numbers are.
Fact 2 is INSUFFICIENT

Final Asnwer: A

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Mike@Magoosh: GMAT Instructor; Posts: 768; Joined: Wed Dec 28, 2011 4:18 pmFollowed by: 140 members; Location: Berkeley, CA; Thanked: 387 times

by Mike@Magoosh » Tue Aug 27, 2013 4:57 pm

'manpreet singh wrote:Given that the mean of Set A is 10, what is the range of two standard deviations above and below the mean?

(1) One standard deviation above and below the mean ranges from 7 to 13.

(2) The median of set A is 11.

ans a

Dear manpreet singh,
Here's a blog that give several helpful tips about DS:
https://magoosh.com/gmat/2012/standard-d ... -the-gmat/

I hope this helps.
Mike

Magoosh GMAT Instructor
https://gmat.magoosh.com/

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