What is a Fishbone Diagram
A fishbone diagram, also known as an Ishikawa diagram, is a visual method for Root Cause Analysis (RCA) that organizes cause-and-effect actions into categories.
A fishbone diagram is a simple yet powerful way to brainstorm potential causes of problems and how they interact. Using this diagram during your RCA session can help you narrow in on the root cause of your problems. This will give you a comprehensive view of your issues and where you exactly want to focus your problem-solving.
Over time, this diagram was nicknamed the fishbone diagram due to its resemblance to a fish skeleton laying on its side. The mouth represents the problem itself. While each of the bones into the spine represents a specific category of potential contributors to the problem.
While the categories can change, the most used are:
- People - persons associated with the process.
- Machine - all elements related to the machines used in a process.
- Method - process review of documents and instructions.
- Measurement - techniques used to measure a part or process meets the desired standards.
- Material - captures the materials involved in the given process.
- Environment - work area surroundings in the process.
Under each category is where you add elements that could impact the process associated with that cause. Please keep in mind that each category may also have sub-causes as well.
Tips When Using a Fishbone Diagram
- The “five-whys” technique is often used in conjunction with the fishbone diagram. You want to keep asking why until you can eventually get to the root cause.
- When you are brainstorming causes, consider having team members write each cause on sticky notes, going around the group asking each person for one cause. Continue going through the rounds, getting more causes, until all ideas are exhausted.
- To help identify the root causes from all the ideas generated, consider a multi-voting technique such as having each team member identify the top three root causes. Ask each team member to place three tally marks or colored sticky dots on the fishbone next to what they believe are the root causes that could potentially be addressed.