Question 711148: A vaccine has a 90% probability of being effective in preventing a certain disease. the probability of getting a certain disease if a person is not vaccinated is 50%. In a certain geographic region, 25% of the people get vaccinated. If a person is selected at random, find the probability that he or she will contract the disease.
Answer by srinivas.g(540)   (Show Source):
You can put this solution on YOUR website! % of the people vaccinated = 25%
But vaccine has a 90% probability of being effective in preventing a certain disease.
% probability not being effective = 10 %
% people may get disease = 25% * 10% = 2. 5%
75 % of the people has not vaccinated
the probability of getting a certain disease if a person is not vaccinated is 50%
% people may get disease = 75 % * 50 %
= 37.5 %
total % of people may get disease = 37.5 %+ 2.5 %
= 40 %
so 0ut 0f 100 people , 40 people may get disease
Hence If a person is selected at random, find the probability that he or she will contract the disease is 40 / 100
=4/10
=2/5 or simply 40 %
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