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156 Decision trees and influence diagrams
Stage 1
Stage 2
Stage 3
Stage 4
Stage 5
Figure 6.9 – Phases of a decision analysis
The decision analyst constructs
a (provisional) representation
of the problem
Iterative feedback to the
decision maker
If agreement If disagreement
Decision analyst elicits
subjective probabilities and
utilities from the decision maker
Decision analyst combines the
probabilities and utilities using
normative decision theory
Normative decision theory
specifies optimal decisions
What determines the decision analyst’s provisional representation of
the decision problem? Generally, it will be based upon past experience
with similar classes of decision problems and, to a significant extent,
intuition. To quote von Winterfeldt: 13
Often the analyst decides on a specific structure and later finds it unmanageable
... knowing about the recursive nature of the structuring process, it is
good decision analysis practice to spend much effort on structuring and to
keep an open mind about possible revisions.
However, problem representation is an art rather than a science, as
Fischhoff 14 notes:
Regarding the validation of particular assessment techniques we know ...
next to nothing about eliciting the structure of problems from decisionmakers.