The dice role is random. So each die consists of a set {1
.. 6}. Knowing what was rolled on one die provides no information on what was rolled on
the second die. Pretend the die A is labeled {1 ..6 } while die B is labeled { A .. B }.
There is no union between these two sets, so the event of rolling the die remains
independent. So the answer to your question is that, yes events A and B
are independent.
You can see this by examining the
conditional probability. Two events are independent
if:
P(A|B) = P(A)
P(A|B) = 1/2
= P(A)
P(B|A) = 1/2 =
P(B)
If A and B were on the same die,
the answer would be different.
The standard definition
of independence is:
Two events A and B are independent if
and only if Pr(A ∩ B) = Pr(A)Pr(B).
A is the set: {1,3,5}
--> P(A) = 1/2
B is the set: {1,2,3,5} -->
P(B) = 2/3
A ∩ B is the set : {1,3,5} --> P(A ∩ B) =
1/2
Pr(A ∩ B)
≠ Pr(A)Pr(B)
Therefore these events are
not independent.
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