Question

*You will use the following scenario forquestions 1-4*On the Wechsler Adult IntelligenceScale a mean IQ is 100 with a standarddeviation of 15. You may assume thatIQ scores follow a normal distribution.What percent of people have an IQscore less than 90?*Write your answer as a percent andround to 2 decimal places*

Answer 1

The Solution:

Given:

`\begin{gathered} x=90 \\ \mu=100 \\ \sigma=15 \end{gathered}`

By formula,

`Z=(x-\mu)/(\sigma)=(90-100)/(15)=(-10)/(15)=-0.6667`

From the z-score tables:

`P(Z\leq90)=0.25248`

Convert to percent by multiplying with 100.

`0.25248*100=25.248\approx25.25\text{\%}`

Thus, the number of people that have an IQ score less than 90 is 25.25%

Therefore, the correct answer si 25.25%