How to Elicit Many Probabilities

In building Bayesian belief networks, the elic­ itation of all probabilities required can be a major obstacle. We learned the extent of this often-cited observation in the construc­ tion of the probabilistic part of a complex influence diagram in the field of cancer treat­ ment. Based upon our negative experiences with existing methods, we designed a new method for probability elicitation from do­ main experts. The method combines various ideas, among which are the ideas of transcrib­ ing probabilities and of using a scale with both numerical and verbal anchors for mark­ ing assessments. In the construction of the probabilistic part of our influence diagram, the method proved to allow for the elicita­ tion of many probabilities in little time.