## anonymous one year ago So which notation do I use? Which of the following is the appropriate notation when calculating conditional probabilities?

1. anonymous

2. anonymous

And is 'union' interchangeable with 'and'?

3. Michele_Laino

no, since "union" is interchangeable with "or"

4. anonymous

So that would be the upside union sign then?

5. Michele_Laino

"intersection" is interchangeable, with "and", and its symbol is the upside union symbol

6. anonymous

Okay, so then can I eliminate option B as a possible answer?

7. Michele_Laino

yes!

8. anonymous

Sweet! And also A as it has a union sign or no?

9. Michele_Laino

in order to compute the conditional probability, we can eliminate the first two options

10. phi

To answer this one, you need to know the definition of conditional probability some of the choices are correct, but not related to conditional probability

11. anonymous

Okay, thanks.

12. anonymous

Oh, the answer is C Because it needs to be over P(A) not P(B) which in this case is C and D, respectively.

13. anonymous

Correct?

14. Michele_Laino

I think that C is not the answer since the conditional probability involves the probabilities of 2 correlated or uncorrelated distinct events

15. anonymous

Oh, you're right. It would be over P(C) if C was the second term. But it is P(C | D) not P(C | C). I get it, thank you @Michele_Laino

16. phi

P(C | D ) means probability of C given that D occurs it is the intersection of C and D divided by the chance of D occuring

17. Michele_Laino

:)

18. anonymous

*not P(D | C)

19. Michele_Laino

the definition of conditional probability is: $P\left( {C \cap D} \right) = P\left( D \right)P\left( {C|D} \right)$ namely the probability for intersection, is equal to the probability of the first event D times the probability of the other event C, when D is occurred