One individual is randomly selected from 500:
         Wrinkles       Wrinkles
         Prominent    Not Prominent
Heavy Smoker 120          60
Light Smoker 75           245
(a) Given that the individual is a heavy smoker, what is the
probability that he/she does not have prominent wrinkles?
(b) What is the probability that the selected individual is a
heavy smoker or has prominent wrinkles?

                     Solution


(a)  Given that the individual is a heavy smoker, we look into the first line 
     in the table, only, and take the values from there.


     Doing this way, for the probability under the question, we get

         P =  =  = .    ANSWER




(b)  In (b), the individual is randomly selected from the total of 500.

     Therefore,  P =  =  = 0.51.    ANSWER