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Old 05-27-2011
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Stats Another question about Normal Gaussian Distribution

The purpose of a study by Luglie et al was to investigate the oral status of a group of patients diagnosed with thalassemia major (TM). One of the outcome measures was the decayed, missing, and filled teeth index (DMFT). In a sample of 100 patients, the mean DMFT index value was 18 with a standard error of 1.2.

What percentage of people will be in the interval [6, 42]?


a) 50%
b) 68.2%
c) 81.8%
d) 99.7%
e) more information is need it
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Old 05-27-2011
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SE=SD/square root of n
so SD=SE x square of n
=1.2x10(squareroot of 100)
SD=12
As mean is 18 ,so 6 will be 1 SD below the mean and 42 will be 2SD above the mean
1SD above and below the mean is equal to 68%
and as 42 is 2SD above the mean we will add 13.2%
So ,answer will be 81.3%
in simple words,34+34+13=81%
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Old 05-27-2011
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Quote:
Originally Posted by struggle View Post
SE=SD/square root of n
so SD=SE x square of n
=1.2x10(squareroot of 100)
SD=12
As mean is 18 ,so 6 will be 1 SD below the mean and 42 will be 2SD above the mean
1SD above and below the mean is equal to 68%
and as 42 is 2SD above the mean we will add 13.2%
So ,answer will be 81.3%
in simple words,34+34+13=81%
I spent over 10 minutes trying to answer this question!...now I see why my answer was wrong
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  #4  
Old 05-27-2011
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Correct Answer

Answer should be c, explained accurately by struggle -81%
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  #5  
Old 05-28-2011
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YES, the correct answer is indeed C).

point to remember: SD is not the same as SE
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