NPT: node probability table

Every node A in a BBN an associated Node Probability Table, the size of which is determined by the number of parent nodes of A. For example, if node A has parent nodes B and C then the NPT for node A expresses the probability p(A|B,C) for all possible combinations of A, B and C. If A has x states, B has y states and C has z states then the NPT has xyz cells. If node A is a root node (i.e. it has no parents), then the NPT simply lists the x prior probabilities for each state of node A..