Assume that aset of test scores is normally distributed with a mean of 100 and a standard deviation of 20 use the 68-95-99?

Answer 1

68% of the scores are within 1 standard deviation of the mean -80, 120

95% of the scores are within 2 standard deviations of the mean -60, 140

99.7% of the scores are within 3 standard deviations of the mean -40, 180