I am absolutely stumped. I have a take-home final for quantitative analysis and quality control that is due tomorrow and there are a few questions that I can't figure out. (I wish I had thought to ask my professor which part of statistics to use to help me but too late now)


In the United States, the 4 blood types (O,A, B, and AB) are distributed as follows:
Type O: 45%
Type A: 40%
Type B: 11%
Type AB: ?

a. What proportion of this population have type AB blood?
b. If a citizen is chosen at random, what is the probability that they have type A or type B blood?
c. If 3 citizens are chosen at random, what is the probability that they have type A or type B blood?
d. If 5 people are chosen randomly from the entire population, what is the probability that NONE have type O blood?


I know this looks like I'm asking you to do my assignment for me, but I really need help. If anyone can give me some hints or formulas, that would be great. Answers with the explanations would be awesome, that way I can use this question to answer others. (I'm the kind of person that does better with examples and simple instructions instead of long, drawn-out instructions)



Thanks for the answers galactus, I fixed part c so hopefully you can help me out now!

For part a, the probabilities must add to 1.

Part b, add the probs for type A and B

Part c, you have 3 but said 'both'. Do you mean 2 instead of 3?

Part d. 55% do not have O. So, the prob of choosing 1 person without O is .55

What about for 5 people?

Now that you've fixed part 3 and you have the solutions to the other questions, you should be able to solve part 3 on your own... considering this is your take home final.