Answer:
2.5% of adults are intellectually disabled by this criterion
Step-by-step explanation:
The Empirical Rule(68-95-99.7 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 = 105
Standard deviation = 16
The normal distribution is symmetric, which means that 50% of the measures are below the mean and 50% are above.
What percent of adults are intellectually disabled by this criterion
Below 73
73 = 105 - 2*16
So 73 is 2 standard deviations below the mean.
Of the 50% of the measures that are below the mean, 95% are within 2 standard deviations of the mean, that is, between 73 and 105. The other 100 - 95% = 5% are below 73. So
0.05*0.5 = 0.025
0.025*100 = 2.5%
2.5% of adults are intellectually disabled by this criterion
