Question

The Intelligence Quotient (IQ) test scores are normally distributed with a mean of 100 and a standard deviation of 15.  Given a class with 12 students, what is the probability that the class' average IQ score is less than 115?

Answer 1

Solution :

Given that ,

mean =   = 100

standard deviation = = 15

n = 12

= 100

=  / n =15 / 12=4.3301

P( <115 ) = P[( - ) / < (115 -100) / 4.3301]

= P(z <3.46 )

Using z table  

= 0.9997   

probability= 0.9997