Relation diagram in new 7 QC tools

A relation diagram is also known as an inter-relation diagram. It is a tool that finds solutions to problems or projects that have complex cause-and-effect relationships. It helps to identify the cause and find a logical relation. A relation diagram is a creative process that allows multi-directional thinking.

When is a relation diagram used?

Below are the situations when relations charts are used:

  • At the planning stage find out the overall view of the problem.
  • To identify an area of most impact for improvement
  • When a complex problem needs to be solved
  • After preparing the Affinity diagram, Cause and effect diagram or Tree diagram to find out the relations of ideas.

Benefits of a relation diagram:

  • To facilitate common consent among team members.
  • Enable priority to be identified
  • Help to develop and change the thinking of the people.

How to make a relation diagram?

Write a statement defining the problem that the relation diagram will dignose. Write on a card or sticky note and place it on the top.

Brainstorm ideas about the problem and write them on the cards or sticky notes.

Place one idea at a time on the work surface and check that this idea relate to others. Place ideas that are related near the first. Leave space between the cards to allow for drawing arrow later. Repeat until all cards on the work surface.

For each idea check the relation of that idea to others. Draw arrows from each idea to the one it causes or influences. Repeat the check for each idea.

Analyze the relation diagram:

  • Count the arrows in and out for each idea. Write the counts at bottom of each box. The idea with the most arrows is the key idea.
  • Check which idea has primary outgoing arrows. These are the basic causes.
  • Note which ideas have primarily incoming arrows. These are final effects that also may be critical to address.

Also idea with less arrows are key ideas. The number of arrows is only an indicator, not an absolute rule. Draw bold lines around the key ideas.

You make like to read about Scatter Diagram, Cause and Effect Diagram & Tree Diagram.

Example of Relation Diagram:

A company is planning to install a new Robot for welding assembly line. The team in the company draw a relation diagram to sort out a confusing set of elements involved in this project.

Relation diagram for installing welding robot
Relation Diagram example

“Install new robot welding assembly” is the card identifying the project/issue. The ideas that were brainstorms were a mixtures of action steps, problems, results and effect to be handled. All these ideas clubed in the diagram together. As the question asked about relationship and causes, the mixture of ideas began to sort itself out.

After all the arrows were drawn, key issue became clear. They are outlined with bold lines.

  • New Software has one arrow in and four arrows out. Install a new robot that has one arrow in and four arrows out. Both ideas are the basic causes.
  • Increase processing cost has two arrows in and negotiate maintenance cost has three in. The team identified them as key effects to avoid.

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