In: Statistics and Probability
If A, B, and C events are independent, check if B and A \ C events are independent or not.
A , B , C are the events independent , we have to check if B and A|C are independent or not.
ANSWER :
YES , B and A|C are independent.
SHORT EXPLANATION :
Since , A, B , C are the independent events , so occurence of A have no effect given that the event C has already happened.
p( A|C ) = p ( A ) ................(1)
Now, Since , A, B are the independent events , p ( A B ) = p(A) * P(B) .....(2)
Now , B and A|C are independent if p( A|C B ) = p (A|C) * p(B)
But , p( A|C B ) = p ( A B ) ..........[ From (1) ] ................(3)
From (2) and (3)
p( A|C B ) = p ( A B ) = p (A|C) * p(B)
Therefore, p( A|C B ) = p (A|C) * p(B)
From the above proven statement we can safely conclude that A|C and B are independent.