Question

Assume that adults have IQ scores that are normally distributed with a mean of 100 and a standard deviation of 15. Find the probability that a randomly selected adult has an IQ between 84 and 116.

Answer 1

Solution:

Given that,

mean = = 100

standard deviation = = 15

p ( 84 < x < 116 )

= p ( 84 - 100 / 15) < ( x -  / ) < ( 116 - 100 / 15)

= p ( - 16 / 15 < z < 16 / 15 )

= p (- 1.07 < z < 1.07 )

= p (z < 1.07 ) - p ( z < - 1.07 )

Using z table

= 0.8577 - 0.1423

= 0.7154

Probability = 0.7154