Question

The Intelligence Quotient (IQ) test scores are normally distributed with a mean of 100 and a standard deviation of 15 What is the probability that a person would score between 85 and 115?

Answer 1

Solution :

Given that ,

mean =   = 100

standard deviation = =15

P(85< x <115 ) = P[(85-100) / 15< (x - ) / < (115-100) / 15)]

= P(-1 < Z <1 )

= P(Z <1 ) - P(Z <-1 )

Using z table   

= 0.8413-0.1587

probability= 0.6826