A fishbone diagram is one of the most widely used tools in quality management and is considered one of the Seven basic quality tools. Also known as a cause and effect diagram or an Ishikawa diagram (after its creator, Kaoru Ishikawa), the fishbone diagram can help users identify the many possible causes for a problem by sorting ideas into useful categories and is especially useful in structuring brainstorming sessions. It is called a fishbone diagram because when completed, the chart is shaped like a fish skeleton.
The fishbone diagram has variations with nuanced procedures and outcomes, including:
A) Cause enumeration diagram
B) Process fishbone
C) Cause and effect diagram with the addition of cards (CEDAC)
D) Desired-result fishbone
E) Reverse fishbone diagram
In smaller projects or when immediate action is needed, the fishbone diagram may be the only tool used to determine the root cause(s) of a problem and guide actions. For complex problems, however, it may be one of several tools used in the improvement process alongside others like a responsibility matrix or an action-planning matrix.
How to create a fishbone diagram:
1) Define the Problem:
Write down the problem or effect you want to analyze at the head of the fish (the right side of the diagram).
2) Draw the Backbone:
Draw a straight horizontal line (the backbone) pointing to the problem statement.
3) Identify Major Categories:
Draw several diagonal lines (the ribs) branching off from the backbone. Use the 6 M’s or 4 P’s from above as a starting point, but feel free to modify them as needed for your process and situation.
4) Brainstorm Causes:
For each category, brainstorm potential causes of the problem. Write these causes as smaller lines branching off from each rib. Make sure you invite a cross-functional team to participate to generate as many ideas as possible.
5) Analyze the Diagram:
Review the diagram to identify relationships and prioritize causes for further investigation. You can prioritize using actual data, multivoting, nominal group techniques, or gaining consensus from the team.
6) Determine root causes:
Use 5 Whys to breakdown each of the prioritized causes further until you reach the root cause (process breakdown).
7) Take Action:
Use the insights gained to develop solutions or action plans to address the root causes identified.
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