A piece of equipment fails repeatedly in one month. A report of the same issue keeps resurfacing even after it has been resolved. A project fails to meet its deadline for the fourth time in a row. When faced with these issues, teams often opt for the simplest solution and get on with their work. A few weeks later, the issue arises again. As it turns out, no one actually pinpointed why the problem occurred in the first place.
This gap between reacting to symptoms and systematically investigating possible causes is what a fishbone diagram helps teams fix.
What Exactly Is a Fishbone Diagram
A fishbone diagram is a visual tool, also called the Ishikawa diagram or the cause-and-effect diagram. It is used for organizing the potential causes of a specific problem. Those causes are listed on the diagram’s branches.
The diagram was introduced by the Japanese quality expert Kaoru Ishikawa in the 1960s and became one of the basic tools used in quality management.
Teams use it for brainstorming, analyzing process-related problems, figuring out key causes, and determining additional information for further analysis. A fishbone diagram does not confirm the responsible cause on its own.
How Fishbone Diagrams Support Problem Solving
The fishbone diagram helps sort brainstorming into categories. This allows teams to consider different areas of a process rather than focusing on a single type of cause.
In industry and production, the 6M categories are frequently used for initial assessment:
| Category | Elements of it |
| Manpower | Lack of training, unclear roles, skill sets, weariness, and communication issues |
| Machine | Condition, calibration, maintenance, tooling, and technology gaps |
| Method | Process stages, work instructions, standards, and inconsistency |
| Material | Quality of inputs, supplier differences, wrong materials, and storage conditions |
| Measurement | Checking methods, wrong measurements, and broken tools |
| Mother Nature or Environment | Weather, humidity, vibration, dust, etc. |
These categories provide a basis for analysis, but they do not represent a rigid set of rules to follow. Different teams can also use Lean Six Sigma templates to organize their analyses.
Fishbone Diagram vs. Other Root Cause Analysis Tools
The fishbone diagram has a different application than other root cause analysis (RCA) tools. Each method has its own stage of application in an investigation.
| Tool | Main function | When it is used |
| Fishbone Diagram | Divides contributing causes into categories | The investigation has several possible drivers across different sections of the process |
| 5 Whys Method | Offers a way to investigate by identifying a cause-and-effect chain through repeated questioning of “Why?” | There is a relatively linear cause-and-effect chain |
| Pareto Chart | Provides a list of causes or defects in order of prevalence | The team has data and needs to prioritize problems based on their severity or frequency |
| 8D | Renders a structure for correcting and preventing recurring problems | A formal process for corrective actions is needed |
| A3 | Combines aspects such as defining the problem, analyzing causes, providing countermeasures, and following up on them | The company wants to have a clear improvement plan |
Final Thoughts
Although a fishbone diagram is not a problem solver in itself, it cuts out the chance of getting stuck on the first explanation.
When combined with data gathering, 5 Whys, Pareto principle analysis, and the DMAIC toolkit, it becomes part of a repeatable continuous improvement paradigm.
The ability to apply these techniques to actual business processes can be developed through formal training for Lean Six Sigma Green Belt certification.
Spoclearn offers corporate training solutions, consulting, blended training, and post-training support for professionals looking to fine-tune their work processes.
FAQs
1. Does the fishbone diagram mean root cause analysis?
No, root cause analysis is a broader process of finding the reason behind a setback. The fishbone diagram is one of the tools used to uncover what is driving the problem.
2. Who uses fishbone diagrams?
Quality professionals, project managers, operations teams, engineers, IT specialists, health care professionals, and customer care leaders can use fishbone diagrams. The tool is especially useful when an issue keeps recurring and may involve a range of factors.
3. Can the fishbone diagram be applied to the manufacturing area only?
No. Although the fishbone diagram is generally associated with quality and manufacturing, its categories can be adapted for health care, IT, project management, customer service, marketing, and other areas of business.