1. A method, comprising executing computer executable instructions by one or more processors for automatically determining a multinomial distribution in a Bayesian network, the method further comprising: constructing a graphical structure of a Bayesian network using a set of joint probability parameters associated to the constructed Bayesian network structure; designing an automatic procedure to determine values associated with said joint probability parameters; simultaneously deriving an equivalent mean Bayesian network or a class of Bayesian networks; and performing quantitative predictions and reasoning simulations using the equivalent mean Bayesian network or the class of Bayesian networks.