Answer: 16%
Explanation:
Since the IQ scores for adults age 20 to 34 years are normally distributed, we would apply the formula for normal distribution which is expressed as
z = (x - µ)/σ
Where
x = IQ scores for adults age 20 to 34 years.
µ = mean score
σ = standard deviation
From the information given,
µ = 120
σ = 20
We want to find the probability of people in this group scored above 140. It is expressed as
P(x > 140) = 1 - P(x ≤ 140)
For x = 140,
z = (140 - 120)/20 = 1
Looking at the normal distribution table, the probability corresponding to the z score is 0.84134
P(x > 140) = 1 - 0.84134 = 0.15866
Approximately 0.16
Therefore, the percent of people in this group scored above 140 is
0.16 × 100 = 16%