Many of the methods used for dealing with uncertainty in expert systems are based on Bayes' Theorem.
|P(A)||Probability of event A|
|P(A B)||Probability of events A and B occurring together|
|P(A | B)||Conditional probability of event A|
|given that event B has occurred|
If A and B are independent, then P(A | B) = P(A).
Expert systems usually deal with events that are not independent, e.g. a disease and its symptoms are not independent.
P (A B) = P(A | B)* P(B) = P(B | A) * P(A) therefore P(A | B) = P(B | A) * P(A) / P(B)
Contents    Page-10    Prev    Next    Page+10    Index