Answer:
110
Step-by-step explanation:
We have been given that the mean IQ score is 100 and the standard deviation is 15.
We will use normal distribution table to solve our given problem.
The top 25% of the population will represent scores greater than 75%.
The z-score corresponding to data greater than 75% is 0.6745.
Upon substituting our given values in z-score formula, we will get:
[tex]z=\frac{x-\mu}{\sigma}[/tex]
[tex]0.6745=\frac{x-100}{15}[/tex]
[tex]0.6745*15=\frac{x-100}{15}*15[/tex]
[tex]10.1175=x-100[/tex]
[tex]10.1175+100=x-100+100[/tex]
[tex]110.1175=x[/tex]
Therefore, the top 25% of the population (ranked by IQ score) have IQ’s above 110.
