Question

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 quantiles: 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 1

40 60 80 100 120 140 160

This represents +/- 3 standard deviations.

68% falls within 80 and 120
95% falls within 60 and 140
99.7% falls within 40 and 160

Using this information and a diagram, I think you will be able to answer wthe questions.

Answer 2

a.percentage of scores less than 100