Closely related to decision trees and often used in conjunction, Influence Diagrams are a
summary of information contained in a decision tree. They involve 4 variable types for
notation: a decision (a rectangle), chance (an oval), objective (a hexagon), and function
(a rounded rectangle). Influence diagrams also use solid lines to denote influence.
Their appearance is much like that of a flowchart.
Influence Diagrams show the dependences between variables. This is an important distinction
between Influence Diagrams and decision trees. Decisions trees offer much more detail about
each possible decision.
If a decision tree is very complex and needs to either be explained to someone or presented, an
Influence Diagram is very helpful.
- Start your tree. Draw a rectangle near the top-left corner of the page; this will be the first node. In this rectangle write the first question or a criterion that leads to a decision.
- Add to the process. Referencing the decision tree, add more boxes to the page as needed, labeling each. A series of decisions, functions, and chances should lead to an objective.
- Add connectors. Draw lines between all related boxes with arrowheads indicating the flow of influence. Each box should be connected to at least one line.
- Verify accuracy. Consult with all stakeholders to verify accuracy.