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

Redeem

Std dev

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 487
Joined: Fri Mar 27, 2009 5:49 am
Thanked: 36 times

Re: Std dev

by dtweah » Mon May 18, 2009 12:14 pm
crackgmat007 wrote:Can someone solve this pls?
Mean: 8.1

1 SD .3

half SD .15

One and half SD .45

8.1 + .45= 8.55 one and half SD above the mean
8.1-.45= 7.65 one and half SD below the mean

Anything in the region [7.65, 8.55] will do. Only 11 are in this region. 7.51 is out of the interval, it is less than 7.65. Everything else is in.

This is a problem which can be missed because one does not organize his or her solution well. ALWAYS REMEMBER THE SD HAS TWO DIRECTIONS: AN ABOVE THE MEAN DIRECTION AND A BELOW THE MEAN DIRECTIOIN.
Top
Legendary Member
Posts: 882
Joined: Fri Feb 20, 2009 2:57 pm
Thanked: 15 times
Followed by:1 members
GMAT Score:690

by crackgmat007 » Mon May 18, 2009 12:47 pm
tx...i did not understand "1.5 standard deviations of the mean". that is why missed it. there was no word asking to multiply 1.5 with SD (such as times)
Top
Post new topic Post Reply
• Page 1 of 1