This week I am continuing my journey through the Lean tool box with a look at the Ishikawa-, Fishbone- or Cause-Effect-Diagram. This method is used to graphically represent cause-effect relationships related to a specific problem. The Ishikawa diagram was developed by chemist Kaoru Ishikawa and initially used to analyze quality problems and their causes.
Why is an Ishikawa diagram so useful?
The diagram and the associated analysis process are used to systematically and comprehensively identify problem causes and effect relationships. The beauty of it is that it is an easy-to-use technique that presents the results concisely and visually. Thus, the analysis is transparent for all people involved and can be referred to again and again during a project as a reference.
How do I create an Ishikawa diagram?
🐠 Preparation: Start by drawing the diagram as an arrow from left to right on your board (or a large brown paper). At the right end of the arrow is the goal (the problem to be solved). The more specific the problem statement is formulated, the better. Then draw the "fish bones" and label them with the main influencing dimensions (the so called 8Ms): Material, Machine, Method, huMan, Measurement, Management, environMent and Maintenance.
🐠 Elaboration of the main and sub causes: The possible causes for the problem are now explored with the team. Various creativity/analysis techniques can be used here, such as the 5Ws. Main causes are placed on the large branches, and smaller branches are added for sub-causes. In this way, as the discussion progresses, the branching increases. Finally, verify that all possible causes have been identified.
🐠 Weighting of the causes: The identified potential causes are now assessed in terms of their significance and influence on the problem. For this purpose, existing data analyses must be used, e.g., to determine likelihoods. Further confirmation of having found the relevant causes can be gained from the input of the experts involved. The most important causes are marked and form the basis for the definition of measures in a next step.
And as always, the more diverse the team, i.e., the more different experiences and skills are represented, the greater the likelihood that all cause-and-effect relationships will indeed be discovered.
Have you also worked with Ishikawa diagrams? Which experiences have you gathered using them?