IQ scores for adults age 20 to 34 years are normally distributed according to N (120, 20). About what percent of people in this group scored above 140?

68%

34%

16%

13.5%

2.5%

Answer: 16%

Step-by-step 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%