A Cause and Effect Diagram (also known as Fishbone Diagram) is a tool used to analyse and iidentify the causes responsible for errors to occur. It is useful in identifying all the possible causes, so that data about them can be collected and analyzed for verification. The causes identified in a cause and effect diagram is based on trust, experience and knowledge of the people involved in putting it together. In instances where data analysis is not possible, cause and effect diagram may also be used (with caution) to identify root causes.
Steps to create a Fishbone diagram
- State the problem or effect at the ‘head’ of a fishbone diagram
- Develop categories and label them at the ‘main bones’ of the diagram
- Brainstorm and record possible causes to the problem under each category
- Drill down if there are possible sub-causes
- If there are too many possible causes, use multi-voting techniques to narrow down
The categories in a fishbone can take many forms. Their main purpose of categories is to provide a structure for the brainstorming process and also to provide a wider perspective as to what can result in the problem. For manufacturing process, it is common to use the MMMMEP categories (Machine, Method, Material, Measurement, People and Environment). For transactional or service processes, the 4P categories (Policy, Procedures, People and Place) are used.
The usage of the cause and effect diagram is fairly flexible and it depends on the creativity of the user. Some of the other applications are:
- Using the main steps of the process as categories and identify possible causes for each step
- Using separate diagrams to identify causes that result in variation and mean
- Using multi-level cause and effect diagram to analyse complex problems and drill down to root causes
Create Fishbone using mind mapping tool