Assume that adults have IQ scores that are normally distribu

Assume that adults have IQ scores that are normally distributed with a mean of

102 and a standard deviation of 15. Find the third quartile Q3, which is the IQ score separating the top 25% from the others.

The third quartile,

Q3,

is

___

(Round to one decimal place as needed.)

Solution

P(X<c)=0.75

--> P((X-mean)/s <(c-102)/15)=0.75

--> P(Z<(c-102)/15) = 0.75

--> (c-102)/15= 0.67 (from standard normal table)

So c= 102+0.67*15 =112.1

Answer: 112.1