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christoph
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 09:53
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The mean weight of 500 male students at a certain school is 150 lbs. and the standard deviation is 15 lbs. Assuming that the weights are normally distributed, how many students weight (a) between 135 and 165 lbs., (b) more than 180 lbs. or less than 120 lbs.?



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The mean weight of 500 male students at a certain school is 10 Feb 2005, 10:53
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There's been a long time since I have had my statistics courses so I googled this from the web:


Quote:

All normal density curves satisfy the following property which is often referred to as the Empirical Rule.


68% of the observations fall within 1 standard deviation of the mean, 95% of the observations fall within 2 standard deviations of the mean,
99.7% of the observations fall within 3 standard deviations of the mean.
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(a) between 135 and 165 lbs.,
This is 1s, so 68%

(b) more than 180 lbs. or less than 120 lbs.?
This is 2s, so 1-95%=5%

GMAT will NOT test on this.
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 11:16
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Thanks for that refresher Hong
Good to know.
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mantha
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 11:23
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I agree with your answers - 68% and ~4%. However, the basic normal distribution is not out of scope.
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Folaa3
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 14:21
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HongHu
There's been a long time since I have had my statistics courses so I googled this from the web:


Quote:

All normal density curves satisfy the following property which is often referred to as the Empirical Rule.


68% of the observations fall within 1 standard deviation of the mean, 95% of the observations fall within 2 standard deviations of the mean,
99.7% of the observations fall within 3 standard deviations of the mean.


(a) between 135 and 165 lbs.,
This is 1s, so 68%

(b) more than 180 lbs. or less than 120 lbs.?
This is 2s, so 1-95%=5%

GMAT will NOT test on this.
Show more


Thanks for backing my thoughts cos that was the first thing that came to mind when i saw this questions like...ermmmmm i hope ETS doesn't go this route! :lol:
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 16:24
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mantha ,
you say
Quote:
However, the basic normal distribution is not out of scope.
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Have you heard anybody getting a Normal distribution question in the GMAT? or is it in the OG or practice ETS papers?

Thanks
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Marina
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 17:52
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I don’t think there will be questions on Normal Distributions (or other distributions) on the test. I would assume ETS would need to provide tables for these distributions before giving any questions.
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 20:50
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From OG, page 8.

Quote:

Both types of questions (DS & PS) require knowledge of
arithmetic
elementary algebra
commonly known concepts of geometry
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Paul
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 20:52
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normal distribution is not a GMAT type question
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MA
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The mean weight of 500 male students at a certain school is 10 Feb 2005, 23:07
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(a) 68% of 500 = 340 students.
(b) 5% of 500 = 25 students.



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