How to do a cause and effect diagram?

Imagine that you work in a factory and right now you have a quality problem in production. You’ve tried to solve it several times, but the results remain inconsistent, customers are dissatisfied, and operating costs increase. It’s frustrating, isn’t it? Luckily, we have a solution for you: the cause and effect diagram, a fundamental tool in quality management and problem resolution. 

This diagram, known as an Ishikawa or fishbone diagram, provides a visual structure that helps identify and categorize possible causes that could contribute to an observed problem. Do you want to learn how to design this tool? Keep reading and we’ll tell you! 

Cause and Effect Diagram Features 

The cause and effect diagram was developed by Professor Kaoru Ishikawa in the 1960s and has been a powerful tool for problem analysis ever since. This is a way to organize potential causes into key categories and then conduct a thorough and structured evaluation. Next, we explain the characteristics and elements of the diagram. 

Structure 

The diagram has a structure that resembles the shape of a fishbone, with the effect or problem to be analyzed at the right end of the main line and potential causes grouped in branches extending to the left. 

Categories of causes 

The causes typically fall into broad categories that may include: 

• Personnel (people): Factors related to the people involved. 
• Process: Aspects related to the methods and processes used. 
• Materials, supplies or resources used. 
• Machinery (machines): Equipment, tools or machines involved. 
• Environment (environment): Environmental or contextual conditions. 

Method of use 

To construct the Ishikawa diagram, a work team is assembled that includes people familiar with the problem. Potential causes are then identified through a brainstorming process and grouped into the aforementioned categories. Subsequently, the most relevant causes for the problem in question are analyzed and prioritized. 

When should you use the cause and effect diagram? 

As we have explained before, the cause and effect diagram is a versatile tool that allows you to have a deep and structured understanding of the relationships between various variables that affect a specific problem. Now, don’t you know in what context to apply it? These are some possible scenarios:  

• To solve complex problems: When you are faced with a problem that has no clear or obvious cause, the Ishikawa diagram helps you decompose the problem into different categories of causes to identify all the possible variables that contribute to the undesired effect. 
• In quality and continuous improvement situations: in environments where quality is paramount, such as in manufacturing, service delivery or any process where consistency and efficiency are critical, this tool is essential. Helps find the roots of quality problems to implement effective corrective and preventive actions. 
• For post-incident investigations: After a major incident or failure, the Ishikawa diagram is useful in identifying the root causes that contributed to the adverse event. 
• In improvement and optimization projects: when planning improvements in existing processes or introducing new processes, the cause and effect diagram allows you to anticipate possible challenges and proactively address critical variables that could affect the success of the project. 
• To encourage collaborative analysis: its visual and organized structure facilitates the participation of multidisciplinary teams in problem analysis. This promotes a shared understanding of potential causes and stimulates the generation of creative and effective solutions. 

Steps to make the diagram 

At this point, you may already want to know the steps to make your cause and effect diagram. So we didn’t delay it any longer. Take note! 

• Clearly identify the problem or effect you want to analyze. It is crucial to have a clear and concise understanding of the problem to properly focus the root cause analysis. 
• Decide on the main category under which you will organize potential causes. The choice will depend on the specific context of the problem. 
• Draw a horizontal line extending to the right, representing the backbone of the diagram (the “fishbone”). On the far right, place the effect or problem you are investigating. 
• Host a brainstorming session with a multidisciplinary team to identify all possible causes that could contribute to the problem. Record these causes on lines branching from the main column to the left. 
• For each root cause identified, drill down even further to break down specific sub-causes. This may require further brainstorming sessions or detailed analysis to ensure all relevant variables are captured. 
• As you construct the diagram, make sure that each cause is clearly related to the main effect you are investigating. This ensures that the diagram adequately reflects cause and effect connections. 
• Once the diagram is complete, prioritize the causes according to their potential impact on the problem. This will help you determine where to focus improvement and resolution efforts. 
• Use the Ishikawa diagram as a guide to develop and execute corrective and preventive actions. Be sure to monitor the results of these actions to verify their effectiveness and make adjustments if necessary. 

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