BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

gmat prep - SD, Mean

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 20
Joined: Wed Feb 06, 2008 7:59 am

gmat prep - SD, Mean

by steinbock » Mon Jun 02, 2008 7:37 am
Another one:

If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?

A) 12.0
B) 13.5
C) 17.0
D) 23.5
E) 26.5

OA is A
Top
Source: — Problem Solving |
User avatar
GMAT Instructor
Posts: 85
Joined: Thu May 01, 2008 12:56 pm
Location: Salt Lake City, UT
Thanked: 24 times
GMAT Score:750+

by VP_RedSoxFan » Mon Jun 02, 2008 8:58 am
If the SD is 3.0 and we're looking for the answer choice that is 2.5 stdevs from the mean, then we're looking for an answer choice that is less than 20 - 3*2.5 = 12.5 or greater than 20 + 3*2.5 = 27.5.

Only [A] fits the bill here.

Hope this helps, good luck.
Ryan S.
| GMAT Instructor |
Elite GMAT Preparation and Admissions Consulting
www.VeritasPrep.com

Learn more about me
Top
Master | Next Rank: 500 Posts
Posts: 132
Joined: Tue Oct 07, 2008 4:59 pm
Thanked: 4 times

Range

by vladmire » Sun Nov 02, 2008 12:38 pm
Are there any other ways to come to the same answer. The question asks which value is more than 2.5sd away from the mean. So I will never come up with exactly 12?
Top
Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pm
Thanked: 331 times
Followed by:11 members

by cramya » Sun Nov 02, 2008 1:50 pm
Vladimire,
More than 7.5

Eg: 20-7.5 = 12.5

12 is more than 2.5sd away from the mean.

Lets say choice A was 28 instead of 12 then this would work too since its more than 2.5sd(2.5*3) away

Hope this helps!
Top
Post new topic Post Reply
• Page 1 of 1