The Fishbone Diagram, also known as Ishikawa Diagram, Herringbone Diagram or Cause-and-Effect Diagrams, is a tool to brainstorm, find root causes and visualise the cause and effect of events that happened in a structured way.
One of the Seven Basic Tools of Quality, the Fishbone Diagram is introduced by Kaoru Ishikawa who pioneered quality management processes in the Kawasaki shipyards, and in the process became one of the founding fathers of modern management.
Advantages of using the Fishbone Diagram include:
- Highly visual tool which can branch potential root causes
- Quick to identify root causes that are found multiple times in the same or different area.
- Allows a single overview all causes in one diagram
Disadvantages of the tool include:
- Complex effects with too many causes might become cluttering
- Interrelationships between causes may not be easily identifiable
How to use the Fishbone Diagram
Step 1: Identify the Effect
To begin using the Fishbone Diagram, the Effect is written on the fish’s head, facing to the right.
Step 2: Brainstorm for Causes
The Causes extend to the left as fishbones towards the tail. They branch off the backbone as Areas, and sub-branches to as many levels required to identify Root Causes.
Causes are brainstormed and generated by constantly asking “Why does this happen?” continuously to generate deeper levels of causes.
Step 3: Analyse and validate
Once as many Areas and Causes as possible are brainstormed, you can analyse and identify Root Causes that are addressable as Action Items or repeated in other Areas of the diagram.
Causes can also be further investigated through fact checking, research or surveys to test if they are really contributing to the Effect.
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