Imagine you work in a factory and are currently facing a quality issue in production. You’ve tried to sort it out several times, but the results remain inconsistent, customers are dissatisfied and operating costs are rising. It’s frustrating, isn’t it? Luckily, we’ve got a solution for you: the cause-and-effect diagram an essential tool for quality management and problem-solving.
This diagram, known as Ishikawa diagram or fishbone diagram, provides a visual framework that helps to identify and categorise the possible causes that could be contributing to an observed problem. Would you like to learn how to design this tool? Read on and we’ll tell you all about it!
Features of the cause-and-effect diagram
The The cause-and-effect diagram was developed by the teacher Kaoru Ishikawa in the 1960s and has been a powerful tool for problem analysis ever since. It is a way of organising potential causes into key categories so that a comprehensive and structured assessment can then be carried out. Below, we explain the characteristics and elements of the diagram.
Structure
The diagram is structured in a way that resembles a fishbone, with the effect or problem to be analysed at the far right of the main line and the potential causes grouped into branches extending to the left.
Categories of cases
The causes are typically divided into broad categories, which may include:
- Staff (people): Factors relating to the people involved.
- Process: Aspects relating to the methods and processes used.
- Materials, inputs or resources used.
- Machinery (machines): Equipment, tools or machinery involved.
- Environment (context): Environmental or contextual conditions.
Methodology for use
To construct the Ishikawa diagram, a working group is formed comprising people familiar with the problem. Potential causes are then identified through a brainstorming process and are grouped into the categories mentioned. They are then analysed and prioritise the most significant causes of the problem in question.
When should you use a cause-and-effect diagram?
As we have explained previously, the cause-and-effect diagram is a versatile tool that enables you to gain a deep and structured understanding of the relationships between various variables that affect a specific problem. But are you unsure in what context to apply it? Here 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 to break the problem down into different categories of causes in order to identify all the possible variables contributing to the undesirable effect.
- In the context of quality and continuous improvement: In environments where quality is paramount – such as in manufacturing, service provision or any process where consistency and efficiency are critical – this tool is essential. It helps to identify the root causes of quality issues so that effective corrective and preventive actions can be implemented.
- For post-incident investigations: Following an incident or a major failure, the Ishikawa diagram is useful for identifying the root causes that contributed to the adverse event.
- In improvement and optimisation projects: When planning improvements to existing processes or introducing new ones, the cause-and-effect diagram enables you to anticipate potential challenges and proactively address the critical variables that could affect the project’s success.
- To encourage collaborative analysis: Its visual and structured format facilitates the involvement of multidisciplinary teams in problem analysis. This promotes a shared understanding of potential causes and encourages the development of creative and effective solutions.
Steps for drawing the diagram
At this point, you may already be wondering what steps you need to take to draw up your cause-and-effect diagram. So let’s not delay any longer. Take note!
- Clearly identify What is the problem or effect? that you wish to analyse. It is crucial to have a clear and concise understanding of the problem in order to focus the root cause analysis appropriately.
- Decide what it will be the main category under which you will organise 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»). At the far right, place the effect or problem that you’re investigating.
- Organise a session of brainstorming session with a multidisciplinary team to identify all the possible causes that could be contributing to the problem. Write these causes down in lines branching off from the main column to the left.
- For each root cause identified, dig deeper to break down the specific sub-causes. This may require further brainstorming sessions or detailed analysis to ensure that all relevant variables are taken into account.
- As you draw up the diagram, make sure that each cause is clearly linked to the main effect you are investigating. This ensures that the diagram accurately reflects the cause-and-effect relationships.
- Once the diagram has been completed, prioritises causes according to their potential impact on the problem. This will help you determine where to focus your efforts on improvement and resolution.
- Use the Ishikawa diagram as guide to developing and implementing corrective and preventive actions. Make sure you monitor the results of these actions to check their effectiveness and make adjustments if necessary.
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