Assume that adults have IQ scores that are normally distribu

Assume that adults have IQ scores that are normally distributed with a mean of ?=100 and a standard deviation ?=15. Find the probability that a randomly selected adult has an IQ between 80 and 120.

The probability that a randomly selected adult has an IQ between 80 and 120?is____

(Type an integer or decimal rounded to four decimal places as needed.)

Solution

So the probability is

P(80<X<120)= P((80-100)/15 <(X-mean)/s <(120-100)/15)

=P(-1.33<Z<1.33) =0.8165 (from standard normal table)