SOLUTION: The numbers of pages in the books in a library follow a normal distribution. If the mean number of pages is 180 and the standard deviation is 30 pages, what can you conclude?

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Question 1033517: The numbers of pages in the books in a library follow a
normal distribution. If the mean number of pages is 180
and the standard deviation is 30 pages, what can you conclude?
Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!
In a normally distributed population, by the 
"empirical rule",

1.  68% of the distribution lies within one standard
    deviation of the mean. 

2.  95% of the distribution lies within two standard 
    deviations of the mean. 

3.  99.7% of the distribution lies within three standard 
    deviations of the mean.

Therefore, in that library, we can conclude that: 

1.  68% of the books have between 180-30 or 150 and 
    180+30 or 210 pages.

2.  95% of the books have between 180-2*30 or 180-60 
    or 120 and 180+2*30 180+60 or 240 pages.

3.  99.7% of the books have between 180-3*30 or 180-90 
    or 90 and 180+90 or 270 pages.

Edwin