# Thread: Pretty Basic probability question

1. ## Pretty Basic probability question

Thanks guys. Figured it out!

2. ## Re: Pretty Basic probability question

Originally Posted by TampaBuff
I thought that I would be 1/2 but im not sure if that is right because they are only mutually exclusive and not collectively exhaustive.
You thought what would be 1/2? I see the question asking for 4 things. Which of those things did you think is 1/2 and why?

3. ## Re: Pretty Basic probability question

Originally Posted by Dason
You thought what would be 1/2? I see the question asking for 4 things. Which of those things did you think is 1/2 and why?
Sorry. I thought initially that P(A) would be 1/2, but then I realized that it didnt say anything about being collectively exhaustive. Therefore, I thought that 1/2 would be wrong for part a.

4. ## Re: Pretty Basic probability question

Question: If we know X is a subset of Y then what is ?

If you don't know then drawing a picture might help you out.

5. ## Re: Pretty Basic probability question

Ok thanks. The subset thing was throwing me off. I think I'm at least headed in the right direction now.

So since A is a subset of C, is P(C and not A) = 0 because of the subset?

6. ## Re: Pretty Basic probability question

No. That's not true. Once again draw a picture. I suggest a large circle to represent C and then a smaller circle inside of that to represent A. Now clearly it is possible to have something happen in C without it being inside of A as well so

What I was getting at what that if then

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