We like Ishikawa’s fishbone diagrams also referred to as cause and effect diagrams for good reason. They’re great for figuring out why something isn’t working.
For our clients, it is not uncommon for pre-shipment inspections to uncover trends in failures. When this happens, we want to know why the problem is occurring so appropriate corrective actions can be taken.
We shared a useful four-minute overview of fishbone diagrams some time ago but also decided to put together a general example specific to our experience in the quality industry. ASQ and Mind Tools also have great resources and templates on the subject as well.
The following process took place to create the fishbone diagram example below.
- We talked about the problem and defined it in a way that was specific and relevant. In this case, there were a series of rejected pre-shipment inspections where paint defects were exceeding AQLs as part of the visual evaluation.
- We brainstormed categories that would have an effect on this problem. We read about and do find the use of sticky notes to be a very effective way to organize this information. Also, looking through examples can help with this, as there are a handful of very common categories used. The categories are used as the branches off the main arrow.
- We brainstormed the issues digging deeper into each one and including them where they fit best in the categories. Keep asking why to get a more in-depth evaluation. Layers in the branches can subdivide out the issues further, as necessary.
- We analyzed the diagram and did further research into the causes we listed. When identifying causes and incorporating corrective action, follow-up metrics are very useful in determining if your actions have produced the desired result of effectively resolving the problem you stated.
