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SD!

by Ahmed MS » Mon Oct 31, 2011 9:54 pm
Q: The mean and sd of the 8 nunbers are (shown below) are 10th and 0.3, respectively. What percent of the 8 numbers are within 1 sd of the mean?

9.4, 9.9, 9.9, 9.9, 10, 10.2, 10.2, 10.5

I failed to get the right answer.


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by rijul007 » Mon Oct 31, 2011 10:08 pm
75% ??
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by shankar.ashwin » Mon Oct 31, 2011 10:18 pm
Given S.D=0.3 and Mean =10

Within 1 SD means 10+ 0.3 (or) 9.7-10.3

Of the 8 numbers, 6 of them lie within this range (9.7-10.3)

6/8 * 100 = 75%
Last edited by shankar.ashwin on Mon Oct 31, 2011 10:19 pm, edited 1 time in total.
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by GmatKiss » Mon Oct 31, 2011 10:19 pm
IMO: 75
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by Ahmed MS » Mon Oct 31, 2011 10:47 pm
shankar.ashwin wrote:Given S.D=0.3 and Mean =10

Within 1 SD means 10+ 0.3 (or) 9.7-10.3

Of the 8 numbers, 6 of them lie within this range (9.7-10.3)

6/8 * 100 = 75%

Thanks for your easy and quick solution.
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