Question

A distribution of scores on an aptitude test is Normally distributed with a mean of 80 and a standard deviation of 5. According to the Empirical Rule (68-95-99.7% Rule). approximately what percent of the values will be between 70 and 90? 75% 68% 99.7% 95%

Answer 1

95%
For 68% :
mean + standard deviation: 80 + 5 = 85
Mean - standard deviation: 80 - 5 = 75

For 95%:
Mean + 2(standard deviation): 80 + 2(5) = 80 + 10 = 90.
Mean - 2(standard deviation): 80 - 2(5) = 80 - 10 = 70.

For 99.7%:
Mean + 3(standard deviation): 80 + 3(5) = 80 + 15 = 95.
Mean - 3(standard deviation): 80 - 3(5) = 80 - 15 = 65
So, the percent of values will be between 70 and 90 is 95%.