Given P(A)=.45, P(B)=.31 calculate:
P(A|B)
P(B|A)
I do not know the source of this problem. I'm simply trying
to find help for a friend. She was having trouble with 4
problems that she was trying to understand. I told her about
the wonderful online math resources that are available. Thank
you for any help in helping her understand these types of
problems.
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P(A|B) means "the probability that A is true if you
are GIVEN that B is true".
You must be given P(A&B), the probability that both A and B
are true at the same time in order to calculate P(A|B) or
P(B|A)
The formulas are
P(A&B) P(A&B)
P(A|B) = 覧覧覧覧 and P(B|A) = 覧覧覧覧
P(B) P(A)
If you had, say P(A)=.45, P(B)=.31 and P(A&B) were, say, .2,
then you could calculate
P(A|B) = .2/.31 = .6451612903
P(B|A) = .2/.45 = .4444444444
But without P(A&B) you cannot calculate these.
Edwin
AnlytcPhil@aol.com
