standard deviation, mean from CAT1 - weird crap...

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 45
Joined: Sun Oct 07, 2007 3:54 pm
Location: Seattle, WA
Thanked: 1 times
:) I got it as I finished typing it up! Anyway, since I already did the work here it is:

7.51 8.22 7.86 8.36
8.09 7.83 8.30 8.01
7.73 8.25 7.96 8.53

A vending machine is designed to dispense 8 ounces of coffee into a cup. After a test that recorded the number of ounces of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in ounces were selected from the data. If the 1,000 recorded amounts have a mean of 8.1 ounces and a standard deviation of 0.3 ounces, how many of the 12 listed amounts are within 1.5 standard deviation of the mean?

4
6
9
10
11

within 1.5 sd means 0.3*1.5=0.45
mean is 8.1
within 1.5 is between (8.1-0.45) and (8.1+0.45) OR:
7.65 < x < 8.55
only one doesn't fit, so 12 - 1 = 11
Eleven is the answer.

GMAT/MBA Expert

User avatar
Site Admin
Posts: 6774
Joined: Mon Feb 13, 2006 8:30 am
Location: Los Angeles, CA
Thanked: 1249 times
Followed by:994 members

by beatthegmat » Sat Oct 27, 2007 11:05 pm
Haha, nice! Glad to hear it came to you while sharing this problem with the community.
Beat The GMAT | The MBA Social Network
Community Management Team

Research Top GMAT Prep Courses:
https://www.beatthegmat.com/gmat-prep-courses

Research The World's Top MBA Programs:
https://www.beatthegmat.com/mba/school

Master | Next Rank: 500 Posts
Posts: 175
Joined: Mon Jul 02, 2007 12:01 pm
Thanked: 15 times
Followed by:1 members

by jangojess » Sat Oct 27, 2007 11:06 pm
rightoo man!!!!!!!!!! u can expect Qs like these in GMAT...have come across similar Qs in mock tests
Trying hard!!!