SOLUTION: Using the 68-95-99.7 rule: Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 68-95-99.7 rule to find the followin

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Question 275401: Using the 68-95-99.7 rule:
Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 68-95-99.7 rule to find the following quantities:
Suggest you make a drawing and label first�
a. Percentage of scores less than 100
b. Relative frequency of scores less than 120
c. Percentage of scores less than 140
d. Percentage of scores less than 80
e. Relative frequency of scores less than 60
f. Percentage of scores greater than 120

Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
Using the 68-95-99.7 rule:
Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 68-95-99.7 rule to find the following quantities:
Suggest you make a drawing and label first�
MAKE the drawing and you will see the answers.
----
100 in the middle of the axis
80 is 1 std to the left; 120 is 1 std to the right
68% between them
60 is 2 std to the left ; 140 is 2 std to the right
95% between them
40 is 3 std to the left ; 160 is 3 std to the right
99.7% between them
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a. Percentage of scores less than 100::::: 50%
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b. Relative frequency of scores less than 120:::(50+34)%
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c. Percentage of scores less than 140:::::(50+47.5)%
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d. Percentage of scores less than 80:::::::(50-34)%
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e. Relative frequency of scores less than 60::::(50-47.5)%
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f. Percentage of scores greater than 120:::(50-34)%
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Cheers,
Stan H.