Belief nets: a cousin to decision trees but easier to understand

A paper by Lefki Giannopoulou and Gavin Lawrence discusses several sophisticated techniques for making better litigation decisions. They explain this technique with an example of a decision tree to think through whether to negotiate a settlement or prepare for trial (See my posts of Jan. 17, 2006 and Oct. 24, 2005 on decision trees.). Decision trees suffer from the disadvantage that the number of alternatives can grow almost exponentially and the tree become unwieldy.

The co-authors discuss an alternative: belief nets. “Belief nets are isomorphic with decision trees but are easier to understand and communicate the relationship of all the elements of the problem, and they can cope with substantial sophistication and complexity.” The example they give from the negotiation-litigation decision has four different circles of different sizes as well as two boxes and a diamond each connected by a variety of solid dotted lines. Each geometric figure matches one of the nodes of the decision tree but it is easier to see the total picture no matter how complex.