What is the ishikawa diagram?
The ishikawa diagram is a tool which helps you to get to the root cause of problems. It is also known as the fish bone diagram or cause and effect diagram. You can use the diagram for any kind of problem.
How do you make an effective diagram?
On the right of the diagram (in the fish head) you write the problem you want to analyze. There needs to be a shared understanding on what the problem is. It is important that everybody agrees that this is the problem that has to be solved now.
On the branches of the fish bone you can use different categories. The categories you choose depend on the situation you are in. These are the categories most often used:
- 5M’s: Machine, Man, Material, Method, Measurement
- 8M’s: 5M’s + Management, Maintenance, Mission
- 8P’s: Product, Price, Place, People, Promotion, Process, Physical evidence, Performance
- 4S: Surroundings, Suppliers, Systems and Skills
You can choose one of these models or mix them up according to your needs. During the first phase of the kaizen you will have acquired input which can help you choose the best branches for your fish bone. I always involve the group in choosing the branches as well. It is important that everybody feels they can use the diagram to analyze the problem effectively.
How do you use the diagram?
- First you need to describe the problem en give each of the branches a name as described above.
- Thenext step is that you start a brainstorm with your team to fill out each of the branches with root causes.
- When one of the root causes is not clearly defined help each other to define it using 5 times why.
- Once the brainstorm is over it is important to look for root causes that have a correlation or causal relationship.
- Thelast step is to prioritize your improvement efforts. You can do this by answering two questions for each cause:
- How big is the contribution of this cause to our problem?
- How easy is it to solve this problem?
5 times why
Advantages of the diagram
- The visual presentation helps the creative thinking process.
- If one cause keeps popping up in different branches, or there is one underlying cause beneath a couple of symptoms, it will become apparent immediately.
- People will be very energized to start working on the problem immediately.
- It helps to understand how other people are effected by the same problem. Thereby giving added urgency to solving the problem.
- It’s visual presentation helps to inform and involve stakeholders.
Disadvantages of using the fishbone diagram
- There can be a lot of causes to one problem. This can make the tool look cluttered. This will make it harder to spot interrelationships between causes. It also makes it harder to decide what to do first. Make sure people do not get dejected by the sheer volume of causes. It shows that this is a problem worth solving.
- People can have their own idea about what should be solved and plot their idea accordingly in the priority matrix. Make sure you ask them why it is this important to them and stay respectful to the person and the group as a whole.
Using the ishikawa diagram to get to the root cause of succes
Instead to using the ishikawa diagram to get to the root cause of a problem you can also use it to get to the root cause of a success. This can help you identify critical success factors for achieving future success. The use of the diagram remains the same (root causes, brainstorm, 5 times why, priority matrix). The focus is on what makes us work well. You ask different types of questions:
- Who or what contributed to this process?
- What enabled this to happen?
- Why was this item critical to our success?
- How did this make a difference to you or the company?
You can also use the ishikawa diagram for a wishbone analysis. Here you do the same, but now you focus on what you need more of to get to the desired state. The causes that come from the success or wishbone analysis can be used to define and focus your improvement efforts.
How to choose?
I have used the problem, success and wish bone analysis based on the needs of the organization and the team. Some people will feel that the success or wish bone analysis is too vague to deliver any results, so i use the traditional fish bone diagram with them. Some people teams are very creative and not very problem focused, with them a success or wish bone diagram can be very effective. Choose the tool which best suits the needs of your customers.
Below you can find two of my favorite resources on these topics.