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 ?=20.

Find the probability that a randomly selected adult has an IQ less than 140.

The probability that a randomly selected adult has an IQ less than 140 is_____.

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

Solution

So probability that a randomly selected adult has an IQ less than 140 is

P(X<140) = P((X-mean)/s <(140-100)/20)

=P(Z<2)

=0.0228 (from standard normal table)