Showing posts with label Conditional Probability. Show all posts
Showing posts with label Conditional Probability. Show all posts

Monday, August 9, 2010

Conditional Probability

Conditional Probability
The conditional probability of an event B will be the probability that the event will occur given the knowledge that an event A has already occurred. This probability is written P(B|A), notation for the probability of B given A. In the case where events A and B are independent to the conditional probability of event B given event A is simply the probability of event B, that is P(B)..
Let us consider the events A and B are not independent, then the probability of the intersection of A and B (the probability that both events occur) is defined by
P(A and B) = P(A)P(B|A).
From this definition, the conditional probability P(B|A) is easily obtained by dividing by P(A):
P(B|A)= P(A and B)/ P(A)
This expression is only valid when P(A) is greater than 0. This could also help us on digestive system diagram