SOLUTION: A placement exam for entrance into a math class yields a mean of 80 and a standard deviation of 10. The distribution of the scores is roughly bell-shaped. Use the Empirical Rule to

Question 69160This question is from textbook Elementary Statistics
: A placement exam for entrance into a math class yields a mean of 80 and a standard deviation of 10. The distribution of the scores is roughly bell-shaped. Use the Empirical Rule to find the percentage of scores that lie between 60 and 80.
This question is from textbook Elementary Statistics

Answer by stanbon(48558) (Show Source):
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A placement exam for entrance into a math class yields a mean of 80 and a standard deviation of 10. The distribution of the scores is roughly bell-shaped. Use the Empirical Rule to find the percentage of scores that lie between 60 and 80.
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60 is 2 standard deviations below the mean.
The emperical rule says there is approximately 90% of normally distributed
data within 2 standard deviations of the mean. Your interval is half of
that because it is the data between the mean and two standard deviations
below the mean. Your answer is 47.5%.
Cheers,
Stan H.