The Fishbone Diagram

What is a Fishbone Diagram?
- A Fishbone Diagram is a “Cause and Effect” diagram. The importance of the FBD is that it uses visual power to highlight the problems and the relationship between problems and their potential sources.
When to use a Fishbone Diagram?
- When a simple approach is needed to reduce the effect of a problem(s);
- When identifying possible causes for a problem;
- When problem-solving has gone stale, and the team needs a fresh approach.

This is a typical example of a Fishbone Diagram template. Generally, there are six major branches (some header titles may be varied):

Material
Man or manpower (People)
Machine
Method (Process)
Measurement
Mother Nature (Environment)

Fishbone procedure

Requires input from a group of people. Use it when the problem is complex, and you are unsure of the most likely cause.

Agree on a problem statement (effect) and write it at the end of the horizontal arrow.
Brainstorm the causes that influence the effect – do this for all categories (branches).
Arrange and strategize the causes. Decide on principle causes and show these as the major branches of the horizontal arrow.
Create sub-branches for the causes. Continue to subdivide all the causes for each branch until all causes are included.
Review the chart to ensure all known causes of variation are included.

Fishbone diagram completed

Fishbone Diagram Example

Once the Fishbone is created, the team should decide:

Do we need to collect data at certain processes?
Do we need to revisit any causes or factors for reconsideration?
Make an action item list for all opportunities and follow through

Good to Great

When a process is predictable (in control), the Fishbone diagram will assist in identifying continuous improvement opportunities for a better process.

Improvement

When a process is unpredictable (out of control), Fishbone can identify areas for continuous improvement by removing non-value-added activities to create a more stable process.