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Consider the student population in a college campus. Assume that 55% of the students are female. Assume that 20% of the male drink and 10% of the female

drink.

(a) Pick a female student at random, what is the probability that she does not drink?

(b) Pick a student at random, what is the probability that the student does not drink?

   (c) Pick a student at random, what is the probability that this student is male and

drinks
Guest Mar 26, 2015
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Consider the student population in a college campus. Assume that 55% of the students are female. Assume that 20% of the male drink and 10% of the female drink.
 
(a) Pick a female student at random, what is the probability that she does not drink?
            10% do drink so 90% do not drink

                    90% or    0.9

(b) Pick a student at random, what is the probability that the student does not drink?
     I am going to let the number of students be x
     female = 0.55x     number of female non-drinkers = 0.9*(0.55x) = 0.495x
     male = 0.45x        number of male non-drinkers = 0.8*(0.45x) =  0.36x
     Prob that the student doesn't drink = (0.495x+0.36x)/x = 0.495+0.36 = 0.855 or 85.5%
    
                       
   (c) Pick a student at random, what is the probability that this student is male and drinks
         male = 0.45x        number of male drinkers = 0.2*(0.45x) =  0.09x
         prob that this student is male and drinks = 0.09x/x = 0.09   or  9%
Melody  Mar 27, 2015

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