Preparing a Proactive Root Cause Analysis with the Ishikawa Fishbone Tool

How to Use theFishbone Tool for Root Cause Analysis

Root cause analysis is a structured team process that assists in identifying underlying factors or causes of an adverse event or near-miss. Understanding the contributing factors or causes of a system failure can help develop actions that sustain the correction.

A cause and effect diagram, often called a “fishbone” diagram, can help in brainstorming to identify possible causes of a problem and in sorting ideas into useful categories. A fishbone diagram is a visual way to look at cause and effect. It is a more structured approach than some other tools available for brainstorming causes of a problem (e.g., the Five Whys tool). The problem or effect is displayed at the head or mouth of the fish. Possible contributing causes are listed on the smaller “bones” under various cause categories. A fishbone diagram can be helpful in identifying possible causes for a problem that might not otherwise be considered by directing the team to look at the categories and think of alternative causes. Include team members who have personal knowledge of the processes and systems involved in the problem or event to be investigated.

The Ishikawa Fishbone Diagram (IFD) is one of seven powerful Quality Management Tools (1. IFD, 2. Check Sheet, 3. Control Chart, 4. Histogram, 5. Pareto Chart, 6. Scatter Diagram, 7. Stratification - flow or run chart) that is typically used to solve problems within organizations. In this webinar, you will learn how to apply IFD’s to capture potential problems before they affect cost, quality, schedule, and customer satisfaction.

Fishbone Diagram Procedure

1) Agree on a problem statement (effect). Write it at the center right of the flipchart or whiteboard. Draw a box around it and draw a horizontal arrow running to it.

2) Identify the major factors and draw four or more branches off the large arrow to represent main categories of potential causes.

Service Industries (The 4 Ps):

•        Policies
•        Procedures
•        People
•        Plant/Technology

Manufacturing Industries (The 6 Ms):

•        Machines
•        Methods
•        Materials
•        Measurements
•        Mother Nature(Environment)
•        Manpower (People)

3) Brainstorm all the possible causes of the problem. Ask: “Why does this happen?” As each idea is given, the facilitator writes it as a branch from the appropriate category. Causes can be written in several places if they relate to several categories.

4) Again ask “why does this happen?” about each cause. Write sub–causes branching off the causes. Continue to ask “Why?” and generate deeper levels of causes. Layers of branches indicate causal relationships.

Why-Why Analysis (The 5 Whys):

It is a method of questioning that leads to the identification of the root cause(s) of a problem. A why-why is conducted to identify solutions to a problem that address it’s root cause(s), rather than taking actions that are merely band-aids, a why-why helps to identify how to really prevent the issue from happening again.

5) Analyze the diagram. By this stage there should be a diagram showing all the possible causes of your problem.

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