Survey
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 38
- Joined: Sat Nov 08, 2008 4:36 am
-
- Master | Next Rank: 500 Posts
- Posts: 496
- Joined: Sun May 04, 2008 11:01 pm
- Location: mumbai
- Thanked: 7 times
- GMAT Score:640
Hi sumit,
Mean is 21
SD is 6
Pat watched television below sd in b/w 1 and 2
SD1=21-6=15
SD2=15-6=9
Answer should be in b/w 9-15
only one option 12.....
Hope it helps....
Mean is 21
SD is 6
Pat watched television below sd in b/w 1 and 2
SD1=21-6=15
SD2=15-6=9
Answer should be in b/w 9-15
only one option 12.....
Hope it helps....
-
- Junior | Next Rank: 30 Posts
- Posts: 29
- Joined: Sun Sep 28, 2008 10:53 am
- Thanked: 1 times
Hey why is it :
SD1 =21-6=15
SD2 =15-6=9
It says SD 0f 6 ...so mean can lie between 21+6 and 21-7 ??
I know i am wrong , but please explain me the concept.
SD1 =21-6=15
SD2 =15-6=9
It says SD 0f 6 ...so mean can lie between 21+6 and 21-7 ??
I know i am wrong , but please explain me the concept.
-
- Newbie | Next Rank: 10 Posts
- Posts: 5
- Joined: Mon Nov 24, 2008 7:12 pm
- Location: California
- Thanked: 1 times
A population can be defined with a mean (in this case, hours of tv watched, or 21 hours) and a standard deviation (which is, how much the population can vary from the mean). In this case, the standard deviation is 6 hours. Meaning that people one standard deviation away from the mean (21 hours) either watch 21-6 hours of TV, or 15 hours, OR they can watch 21+6 hours of tv, which is 27 hours. 2 standard deviations away from the mean implies that 2 standard deviations from the population watches between 21-(6*2), or 9 hours of tv or 21+(6*2), or 33 hours of tv. Remeber this applies to the whole population. But the problem only cares about that one person, who watches between 1 and 2 standard deviations BELOW the mean. that is he watches between 21-6 hours, or 21-(6*2) hours of TV, which is between 9 and 15 hours. Hope i helped
p.s. if you ever have trouble with anything statistics related, try visualizing a bell curve, it always helps me.
p.s. if you ever have trouble with anything statistics related, try visualizing a bell curve, it always helps me.
The MBA Dirt
"Trying is the first step towards failure" -Homer the philosopher and Simpson
"Trying is the first step towards failure" -Homer the philosopher and Simpson