Question

If P(AandB) = P(A) x P(B) when A and B are independant, what does P(AandB) equal when they are not independant?


also, what does it mean if they are independant? When are they not independant?

Answer 1

\[P(A|B) = \frac {P(A\cap B)}{P(B)}\]

and

\[P(B|A) = \frac {P(B\cap A)}{P(A)}\]

Answer 2

Does flipping a heads make it more or less likely that I will flip heads the next time?
Nope. It's exactly as likely.
Does pulling an Ace from a deck of cards make it more or less likely that I will pull an ace the next time?
Yes. There are now only 3 aces in the deck. It changed the probability.

Answer 3

oooooh, thats what the |s mean?
I have them equations written down here :D

Answer 4

If the occurrence of A is dependent on occurrence of B then they are dependent otherwise independent.

Answer 5

so independant is when having one chosen doesn't affect the probability of the other being chosen?

Answer 6

The first kind is independent probability. The two events don't effect each other, like coin flips.
The second kind is dependent probability. The outcome of the first event affects the likelihood of the second event.

Answer 7

thanks ;)