Answer:
5% of people have an IQ score less than 60 or greater than 140
Step-by-step explanation:
The Empirical Rule states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean = 100
Standard deviation = 20
What percentage of people have an IQ score less than 60 or greater than 140
60 = 100 - 2*20
So 60 is two standard deviations below the mean
140 = 100 + 2*20
So 140 is two standard deviations above the mean
By the Empirical Rule, 95% of the people have an IQ between 60 and 140, and 5% have an IQ outside this range, that is, less than 60 or greater than 140.
