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

yuri

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.

beatthegmat · Posted: Sat Oct 27, 2007 11:05 pm Post subject:

Haha, nice! Glad to hear it came to you while sharing this problem with the community.

jangojess · Posted: Sat Oct 27, 2007 11:06 pm Post subject:

rightoo man!!!!!!!!!! u can expect Qs like these in GMAT...have come across similar Qs in mock tests