Get structure in the analysis of the problem
The purpose of doing an analysis with a fishbone diagram is that you can structure the possible causes in different categories. You can decide which these categories are for yourself to fit the analysis, or use pre-defined categories. This could be good to avoid getting stuck on one type of cause directly, without taking into account other possibilities. Here are some examples of pre-defined categories to group different root causes by subject.
4M – common within manufacturing
7M+E – An extended version of the 4M above
4S – for Service businesses
8P – for sales and marketing
- Place and time
- Physical environment
- Productivity and quality
Examples of situation defined categories
- Different parts of a product
- Different areas of a service
- Different components of a machine
- Different steps in a process
Build your fishbone analysis step by step
Most of the time there will be enough to just have 4 bones on the fish for a root cause analysis. But for more complex problems that requires more categories to get the whole picture it is common to use 6 or 8 bones on the fish. You can choose the number of bones on your diagram when you place the order.
Divide the analysis and do it at Gemba
One of the main advantages with using magnetic sheets is that you can take each bone and do the analysis at the point where the problem is – go to Gemba. You can also divide the analysis into groups, and let each group work separately on a pair of bones.
When the analysis is done it’s easy to put the magnetic sheets with the fish bones and build the complete fishbone chart on a whiteboard.