The interrelationship digraph is used to display the interrelated factors in complex, multi-variable problems. It can also be used to display the same information for desired outcomes. It shows graphically the logical relationships between factors. This often shows the sequential, cause and effect relationships. The affinity diagram can be used to provide input to this tool.
The steps for constructing an interrelationship digraph are:
- Place the problem statement or desired outcome in the middle of a large piece of paper, such as, a flipchart.
- Draw a double circle around the statement or outcome.
- Arrange the major items (if using an affinity diagram to feed this, use the title cards) in a circle around the problem statement. Place the cards which have ideas most closely related to the problem nearer the problem, if this can be determined.
- Draw lines between ideas that are related. Put an arrowhead on the end of the line that shows the direction of the cause and effect relationship. Use only one way arrows. The arrow should point toward the effect and away from the cause. Each of the cards should have an arrow pointing toward the problem statement.
- Count the number of arrows leading into and out of each idea card. Place the number of arrows going out of the card, a slash and the number of arrows coming into the card above each card (i.e. number away/number into -3/4).
- The card with the most arrows going out is the key cause factor. Place a double box around it.
- Give each team member a copy of the results and discuss them. Attempt to reach consensus on what are the key drivers to the problem.
- The key idea categories from the interrelationship digraph may be used in the systematic diagram.
Content copied from NC Department of Environment and Natural Resources
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