Fishbone Diagram Explained

Fishbone Diagram Explained History of the Fishbone Diagram The fishbone diagram was first developed by Mr. Kaoru Ishikawa in the 1960s which is why you’ll often hear this tool referred to as the Ishikawa diagram. You’ll also hear this tool referred to as a cause and effect diagram. But, due to its unique appearance, most simply refer to this tool as the fishbone diagram. We’d also like to point out that Mr. Ishikawa’s greatest contribution to the world of continuous improvement was his definition of the 7 quality management tools, several of which we’ve already learned about, namely the fishbone diagram, the histogram, the Pareto chart, the check sheet, the control chart, the flowchart, and the scatter diagram. And while Mr. Ishikawa didn’t invent all of these tools he was the first person to use them together in order to solve problems. How to Create a Fishbone Diagram OK, so that’s a bit of the history behind this tool... now let’s turn our attention towards how to create one. Let me start by explaining that there are a number of different ways to complete a fishbone... as such I’d encourage you to experiment and find the approach that works best for you. But to get you started I’d like to share a roadmap we’d encourage you to begin with. First, you’ll want to get your cross-functional team into the same room while also gathering all the supplies needed. In the video we’re using the SigmaXL software tool to keep things neat and easy to read. With this said, I’d like to strongly encourage you to not use software right away. Instead using some butchers’ paper spread across the wall or a white board with some large sized post it notes as shown to the right are excellent ways to construct fishbone diagrams... especially when working with a large group of people. Then, in the end, if you’d like to create and save an electronic copy of your fishbone diagram software like SigmaXL can be used. Or you can simply snap a picture of your fishbone and file that away. Fishbone Diagram Explained 1 Once you and your team are ready to start the first step is to write the main problem or problem statement being focused on the right side of the diagram while also drawing a box around it. We then draw a long horizontal line and arrow off of this box representing the spine of the fish. In this example, the problem we’re dealing with is late pizza deliveries on the weekends. After this we’re ready to draw in the major cause categories. Again, there are no right or wrong major cause categories... however a good place to start are the 4 to 6 Ms we learned about in our previous module. If you’re dealing with more of a service related problem you might try the 6 Ps which stand for People, Process, Policies, Procedures, Price, and Product. And, again, please feel free to make your fishbone work for your company meaning it’s OK if your major cause categories are different than the one’s we’ve discussed. At this point it’s time for your team to get busy as you develop a list of factors that could be causing or contributing to the problem. Again there are many ways to go about this. One way I personally find effective is to hand out the same colored post it notes and pencils to all team members. I then ask the question, “What’s causing this problem?” I then give everyone 3 to 5 minutes to write down as many ideas as they can on their post it notes, which is sometimes referred to as the nominal group technique. Fishbone Diagram Explained 2 After 3 to 5 minutes I ask everyone to place their pencils down. I then go around and ask each person to share their results by reading them aloud. And as they read a post-it note the team agrees where it should be placed on the fishbone. And if it looks like a cause fits on more than one category we create a duplicate and place it in both places. Once this initial brainstorming process is complete the discussion the team has had will usually drum up additional ideas so I let the team write down additional causes followed by the same process of reading them aloud and placing them on the fishbone accordingly. You can actually repeat this process as many times as you need until it seems the team is out of ideas. The next step of the process is to create the second level of causes. To do this we go through each post it note and ask, “Why does this happen?” In many cases we’ll need to ask “why” several times... I normally suggest stopping at around 5 whys or until the cause is controlled by more than one management level away from the existing team members. Using N/3 to Select Root Causes Once this process is complete we’ll have identified numerous root causes... possibly too many to attack at once. So, at this point the team will need to select the root causes they wish to initially focus on. Depending on team dynamics you can also use a powerful technique called N over 3. To do N/3 you simply count up the number of root causes identified and divide that number by 3. Then, each team member gets that many votes as they select which causes they feel are the most important. So, for example, if there are 18 root causes N would be 18 and by dividing this by 3 we arrive at 6. This is to say that each team member gets 6 votes. Please refer to the teaching video for an example of how this works. Add Kaizen Bursts The last step of the fishbone creation process is to draw a cloud or kaizen burst symbol around the root causes the team has selected to initially focus on keeping in mind that the fishbone process is dynamic in nature meaning we’ll definitely come back to update things as the team learns more and begins to attack additional problems. Fishbone Diagram Explained 3.

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