SOLUTION: Suppose the scores of 500 college freshmen taking Physics 101 are normally distributed. The mean score is 60 out of 100, and the standard deviation is 10. Estimate how many grades

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Question 858075: Suppose the scores of 500 college freshmen taking Physics 101 are normally distributed. The mean score is 60 out of 100, and the standard deviation is 10. Estimate how many grades will fall between the
interval of 30 and 90.
Answer by stanbon(75887) About Me  (Show Source):
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Suppose the scores of 500 college freshmen taking Physics 101 are normally distributed. The mean score is 60 out of 100, and the standard deviation is 10. Estimate how many grades will fall between the
interval of 30 and 90.
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30 is 3 std below the mean.
90 is 3 std above the mean
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Using Chebychev's approximations.....
% of data within 3 std of the mean is at least = 1-(1/3)^2 = 8/9 = 89%
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Cheers,
Stan H.