Cause and effect diagrams were pioneered by Kaoru Ishikawa as a systematic method to think through all the possible causes leading to an effect (usually undesired). Ishikawa diagrams are typically drawn as a ‘fishbone’ where causes (depicted as the ‘bones’) are represented hierarchly. This arrangement promotes considering causes that may not be obvious or might be dismissed prematurely. This has been described as the Completeness Method. They can be really helpful when tackling issues that you not have faced before.
Because Ishikawa diagrams are hierarchial, they are well-suited for capturing in a mindmap. In fact, it is easier to draw and manipulate the relationships with a mindmap than applications like MS PowerPoint. More importantly, mindmaps can provide a better tool for reviewing and documenting progress towards proving which branch is the real root cause of a problem (or effect). In addition, you can use tools like FreeMind|GTD to follow-up on the next actions to validate potential root causes.
Building a Diagram
Start by brainstorming possible causes for the problem along with possible categories (the main bones). Depending on the problem domain, the top level causes may differ. The diagram below uses the ‘6M’ template (often useful for business problems): Method, Man, Management, Measurement, Material, and Machine.
Under each major cause, add the next level of categories until you have homes for the potential root causes you have brainstormed. Notice that your brainstorming starts at the ‘leaf’ end of the hierarchy (bottoms-up) while the Ishikawa diagram builds branches from the problem statement (top-down). The structure of the diagram gives both a stimulus for new ideas and places to collect them.
For complex problems, Ishikawa diagrams can get large as bones are added. If you use a whiteboard for initial brainstorming, take a picture with your phone to help document the work and later recapture it in an application. Better still…
Here is the same example captured in a FreeMind mindmap:
There are a number of advantages to capturing an Ishikawa diagram this way:
- More readable end product
- Can be captured while brainstorming (only do this if you are very comfortable with FreeMind and can move quickly; nothing kills brainstorming like waiting for someone to figure out how to use software…)
- Folding of nodes can be used to focus on a particular category and drive deeper
In addition to these ‘format’ related advantages, there are some really important operational advantages to using a mindmap when meeting with your team to discuss investigations and next steps. For example, focusing on the ‘Man’ branch (click on picture to enlarge):
The team has added two potential root causes to the diagram, along with some related Next Actions (indicated by the * symbol) assigned to some resources (indicated by the @ symbol). This is the notation used by FreeMind|GTD to generate a GTD-style list of Next Actions, which is ideal for using in the team meeting:
After the action items were carried out, the team found these were not valid root causes. Here is where the flexibility of a mindmap is useful; the conclusions and data are documented right in the diagram. Also notice that the just these causes have been closed for investigation. If further brainstorming comes up with a training issue, it can be added to this active branch.
Mindmaps can really extend the usefulness of Ishikawa diagrams in both capturing ideas and following-up and documenting the results. Give them a try!