  The main goal of this paper is to describe a new pruning method for solving
decision trees and game trees. The pruning method for decision trees suggests a
slight variant of decision trees that we call scenario trees. In scenario
trees, we do not need a conditional probability for each edge emanating from a
chance node. Instead, we require a joint probability for each path from the
root node to a leaf node. We compare the pruning method to the traditional
rollback method for decision trees and game trees. For problems that require
Bayesian revision of probabilities, a scenario tree representation with the
pruning method is more efficient than a decision tree representation with the
rollback method. For game trees, the pruning method is more efficient than the
rollback method.
