The normal distribution has a greater percentage of its area close to the mean and much less in the tails.
-Assume that adults have IQ scores that are normally distributed with a mean of 100 and a standard deviation of 15 (as on the Wechsler test). Find P30, which is the IQ score separating the bottom 30% from the top 70%.
A) 92.8
B) 91.4
C) 91.9
D) 92.2

Question

Quizplus · Accepted Answer

To find P30, we need to find the z-score that corresponds to the 30th percentile in a standard normal distribution, which is approximately -0.524. Using the formula X = μ + zσ, where μ = 100 and σ = 15, we calculate X = 100 + (-0.524)(15) ≈ 92.2.

The Normal Distribution Has a Greater Percentage of Its Area