Fishbone Diagram

What is a Fishbone Diagram / Ishikawa Diagram?

A problem can be due to many hidden root cause. Brainstorming sessions is never enough to identify potential root cause. It requires a systematic study of potential factors which can lead to a problem.

The list may seem to be endless and boring to make sometime. But it is easy by using a Fishbone Diagram, Ishikawa diagram or cause and effect diagram. It makes simpler to perform an extensive cause and effect analysis and identifying the root causes of problems.

Fishbone diagram was developed by a Japanese scientist, Kaoru Ishikawa. It was used during the development of Toyota’s manufacturing processes in 1958. The design of the diagram looks much like the skeleton of a fish. Therefore, it is often referred to as the fishbone diagram. It is also called as cause-and-effect analysis.

Goal of Fish bone Diagram-

The main goal is to illustrate in a simple graphical way the relationship between a problem and potential root cause that influence the problem.

Objectives of Fish bone Diagram-

The main objectives of Fish bone diagram tool are-

1.        Determining root causes of a problem.

2.        Focusing on a specific issue without resorting to complaints and irrelevant discussion.

3.        Identifying areas for improvement.

 Fishbone Diagram template

The Fishbone Diagram makes a distinction between cause and result.

The problem is identified and described on the right-hand side of the Fishbone Diagram and potential root causes are denominated on the left-hand side under specific categories. These root causes are divided into four categories. Subsequently, each category may be branched into secondary causes.

The five main categories are:

1.     People

This category denotes all the possible and potential causes of problem by human actions. Few examples - Good communication, SOP followed, employees experienced and competent, Reconstitution of reagents, etc.

2.     Machines

This category denotes problem related to the functioning of machines, equipment and tools at work station. Few examples- equipment calibration, safety, maintenance, etc. 

3.     Materials

This category establishes the possible problems caused with the materials, reagents and consumables. Few examples- Quality of material, Reagent Stability, etc.

4.     Methods

This category investigates whether the work method is the possible root cause of the problem. For example- Adequate processes; SOP availability, variation in processes, etc.

5.     Environment

This category investigates whether the work environment is the possible root cause of the problem. For example- High temperature, Low temperature, ergonomic factors, etc.

Details of the Fishbone Diagram

The following steps come up for discussion:

1.        Identify problem. Note it down on the right-hand side of the Fishbone Diagram.

2.        Brainstorming session to come up with potential causes affecting and causing the problem. Note it down on the left-hand side of the Fishbone Diagram in category-wise.

3.        Highlight main factors contributing the cause of problem.  Add as much possible secondary causes until no more possible causes are left to think of.

4.        Study the Fishbone diagram for the related or derived causes.

5.        Vote for most likely causes. The causes without a vote are deleted.

6.        Prioritize the potential causes according to the number of votes. The highest priority with maximum number of vote should be investigated and dealt further. Step by step goes further down in the order causes will be addressed.

Useful tips for success

•          Make sure that there is consensus in the group about both the need and the characteristics of the cause statement before beginning the process of building the Fishbone Diagram.

•          If appropriate, you can “graft” branches that do not contain a lot of information on to other branches. Likewise, you can split branches that have too much information into two or more branches as you go.

•          Make parsimonious use of words while populating the Ishikawa diagram. Only use as many words as necessary to describe the cause or effect.

Application-

The Fishbone diagram could be applied when it is wanted to:

• Focus attention on one specific issue or problem.

• Focus the team on the causes, not the symptoms.

• Organize and display graphically the various theories about what the root causes of a problem may be.

• Show the relationship of various factors influencing a problem.

• Reveal important relationships among various variables and possible causes.

• Provide additional insight into process behaviors.

Benefits –

1.        Helps determine root causes

2.        Encourages group participation

3.        Uses an orderly, easy to read format to diagram cause and affect     relationships.

4.        Indicate possible causes of variation

5.        Increases knowledge of the process by helping everyone to learn more about the factors at work and how they relate.