5th Edition PMBOK® Guide—Chapter 8: Interrelationship Digraphs


There are seven quality management tools that are listed among the main tools & techniques for Process 8.2 Perform Quality Assurance.    This posts covers the third out of seven tools, Interrelationship Digraphs.   The word “Digraphs” refers to the linking of various pairs of ideas.

The Relations Diagram, also known as an Interrelationship Diagram (or Digraph), is a brainstorming tool for exploring the cause-and-effect relationship between a series of ideas or facts.    It is often used to explore the relationship between a series of ideas that were generated using other quality tools, such as the Affinity Diagram (tool #1), Tree Diagram (tool #4), or the Fishbone or Ishikawa Diagram (one of the quality ools from process 8.1 Plan Quality Management).

Here’s how it works (the methodology is similar to that of Quality Management Tool #1: Affinity Diagrams):

  Step Description
1. Identify Problem Define your problem or identify a general theme. Example: why has customer satisfaction rate been declining?
2. Collect facts/ideas List the relevant facts, data, or ideas, opinions regarding the subject and put these on the post-in notes or index cards. Post these on a noteboard or blackboard.
3. Create groups Notice which of these notes or cards are related to each other similar and arrange them according to patterns based on those cohesive groups.
4. Identify Groupings Label each group of similar notes or cards with a label for each group. These could be aspects of the problem under consideration.
5. Identify Relationships Identify cause-and-effect relationships between various ideas or facts. Draw an arrow if one idea, effect, or fact is caused by another, with the arrow going from the cause to the effect.
5. Analyze Results Look at the number of arrows leading into and the number of arrows leading out of each idea. Those that have the most arrows going out are causes, and those that have the most arrows going in are effects.
6. Share Results Share the results with the stakeholders at large.

The results should show the natural links that emerge among the various issues or presented, and will help the team discover root causes of the problem defined at the beginning.   

 

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