24 Dec 2020

Posted on:

11 Mar 2020

0

# I am not understanding well the available answers for this question "Going back to the card example, which of the following sets of events are independent?"

The answer given to this question "Going back to the card example, which of the following sets of events are independent?" was "Drawing a diamond and drawing an ace". Why? How are these two events independent? There is an Ace-Diamond, right? Why are these two events "drawing a queen and drawing a Jack" dependent? Why are these two events "drawing a four and an ace of spades" dependent? The only events that were clearly dependent were drawing a heart and drawing the Jack of hearts. The other answers were pretty confusing. Please help me out. Thanks a lot.
Instructor
Posted on:

16 Mar 2020

2

Hey Luis,

Thanks for reaching out!

So, in this case we're examining the events in pairs (i.e. A: Draw a Diamond, B: Draw an Ace).

We can state that two events are independent if the conditional and unconditional probabilities are equal (P(A|B ) = P(A)). Hence, if the likelihood of drawing a Diamond (P(A)) is the same as drawing a diamond, provided we knew the card was an Ace (P(A|B )), then the two are independent. In this specific case, P(A) = 1/4 since there are 13 diamonds in the 52-card deck. Simultaneously, there is a single diamond among the 4 aces in the deck, so P(A|B ) = 1/4.

Hence, P(A) = 1/4 =  P(A|B ), so the two are independent.

We can try the same for the other pairs and see that's not the case, so this is the only acceptable answer.

Hope this helps!
Best,
365 Vik

P.S. We're drawing a single card.

Posted on:

24 Dec 2020

0
Hi Vik,   I'm trying to understand the statement when P(A|B) = P(A), then those two events are independent. Could you please elaborate more? Thanks!