## anonymous 5 years ago An urn contains 3 red marbles and 2 blue marbles. Three marbles are drawn together. Let X be the number of red marbles drawn. a) List the probability function of X. b) Find the expected value of X, E(X).

1. anonymous

an urn is what they out the ashes of dead ppl in after they cream-ate them.

2. anonymous

X = number of red marbles P(X) is defined on a domain of 1, 2, and 3 Note: 0 isn't in the domain because it isn't a possible outcome when drawing 3 marbles since there are only 2 non-red marbles. The definition of the P(X) is just the assignment of the probabilities to the 1, 2, and 3 $P(1 red)=\frac{C(3,1)*C(2,2)}{C(5,3)}$ $P(2 red)=\frac{C(3,2)*C(2,1)}{C(5,3)}$ $P(2 red)=\frac{C(3,3)*C(2,0)}{C(5,3)}$

3. anonymous

Oops, the last one should be "P(3 red)"

4. anonymous

Thank you SO much. I had a basic idea of this. The rest would be to just plug in the probabilities in the E(X) formula right?

5. anonymous

E(X) = 1*P(1)+2*P(2)+3*P(3) :)

6. anonymous

Thanks, do you have an email or instant messaging program?

7. anonymous

I'm trying to prepare for finals and there is a lot of probability stuff on this level that I do not understand.

8. anonymous

I would love to help but I don't have a lot of time. :(

9. anonymous

Ah... ok. Thanks anyway.