Probability
posted by Chris .
Every Persons blood belongs to one of four blood groups. The percentage of U.S. blood donors to the Red Cross is given:
Type A=37% B=12.5% AB=3.5% O=47%
a)What is the Probability that the blood of any two unrelated people in a Red Cross blood drive belong to the same group?
Is this correct?
P(Ba)=.37 P(Bb)=.125 P(Bab)=.035 P(Bo)=.47
P(Samegroup)=P(Ba)^2+P(Bb)^2+P(Bab)^2+P(Bo)^2= 0.37465 ?
b)What is the probability that the blood of any four unrelated people in an american red cross blood drive belong to each of the four groups?

a) correct
b) four unrelated people standing in a row. Probability that they are in this exact order: A, B, AB, O is .37*.125*.035*.47 = .0007608
Now then, the number of ways these four people can be rearranged is 4*3*2*1 = 24.
So, Probability is 24*.0007608 = .01826