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Mean and Standard deviation

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Mean and Standard deviation

by nxanand » Mon Apr 19, 2010 9:56 pm
This question is from the GMAT Prep test. I didn't understand what "within 1 standard deviation of the mean" stands for.

Q. 9.4 , 9.9 , 9.9 , 9.9 , 10.0 , 10.2 , 10.2 , 10.5

The mean and the standard deviation of the 8 numbers is 10 & 0.3 respectively. What percent of the 8 numbers are within 1 standard deviation of the mean?

a. 90%
b. 85%
c. 80%
d. 75%
e. 70%
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by liferocks » Mon Apr 19, 2010 10:05 pm
within '1 standard deviation of the mean ' implies whether the absolute value is within mean +/- sd

here this value is 9.7 to 10.3
total 6 of 8 numbers lies in this range
hence ans is 6/8*100%=75%

option D
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Junior | Next Rank: 30 Posts
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by nxanand » Mon Apr 19, 2010 10:11 pm
thanks :)
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