Examples of a fishbone diagram (March 24, 2006)

The fishbone diagram (also called the Ishikawa diagram, or the cause and effect diagram) is a tool for identifying the root causes of quality problems. It was named after Kaoru Ishikawa, the man who pioneered the use of this chart in quality improvement in the 1960's. Surprisingly, I have had to hunt very hard to find any good examples of a fishbone diagram.

Here's one example.

This diagram identifies problems with a speech recognition and interaction system called The Carnegie Mellon Communicator System which is used to automate travel-planning. The major bones are

• System Failure,
• Understanding,
• Task,
• System Output,
• Dialog, and
• Recognition.

 The first two minor bones are

• System Crash, and
• Airline Information Access Error.

This image appears in

• www.speech.cs.cmu.edu/Communicator/papers/eurospeech99-1.pdf

Here's a second example:

This diagram outlines causes of defects in a computer user interface. The major bones are

• Guidelines Not Followed,
• Lack of Feedback,
• Lack of Guidelines,
• Different Perspectives, and
• Oops! (Forgotten).

The first minor bone is

• Don't Read Them

with

• No Time and
• No Central Location

attached as root causes. This diagram appears at

• www.hpl.hp.com/hpjournal/96aug/aug96a2.pdf

and a similar fishbone diagram on specification defects also appears in this article.

I could not find a good medical example that appears on the web. There were some examples in journal articles that do not appear on the web, such as this one:

This diagram does not follow the form but does capture the spirit of the fishbone diagram. The major bones are

• People,
• Environmental & Other,
• Patient Factors,
• Drugs & Devices,
• Technology, and Measures,
• Process Tools & Communication.

The first two minor bones are

• Family and
• RN.

This diagram appears in the following journal publication.

• Management of the agitated intensive care unit patient. Ian L. Cohen, T. James Gallagher, Anne S. Pohlman, Joseph F. Dasta, Edward Abraham, Peter J. Papadokos. Crit Care Med 2002: 30(1 (Suppl.)); S97-S123. [Medline]

The American Statistician has a hypothetical example of a manufacturing environment involving fluid mechanics. Students examine a system that involves dropping a bead into a glycerin/water mix with a few other chemicals like baking soda thrown in. The goal is to produce a drop time of 7.5 plus or minus 01. seconds. As part of preparing a statistical experiment that will identify appropriate manufacturing conditions, students are encouraged to produce a fishbone diagram. Here is the example shown in the article itself.

The major bones are

• Operator,
• Methods,
• Measurement, and
• Materials.

The first minor bone is

• Bead Orientation,

with

• Edge and
• Radius

attached as root causes. This diagram appears in

• Process Improvement Exercises for the Chemical Industry. Dale A. Kopas, Paul R. McAllister. The American Statistician 1992: 46(1); 34-41.

This article also discusses and explores other important Quality Control techniques like the Plan-Do-Check-Act cycle, and Evolutionary Operation (EVOP).

If you want to use a Fishbone Diagram, first list the main problem on the right hand side of the paper. Then draw a horizontal line to represent the "backbone" of the diagram. This line is not labeled. Off of the backbone, draw and label major bones: 4 to 7 major categories of causes. A commonly used list of major causes is Management, Manpower, Machines, and Materials. Another possible list is Policies, Procedures, Plant, and People. Then elicit ideas using an approach like brainstorming to place individual causes as minor bones on each major bone. Some people allow the individual causes to have subcauses, which would be attached to the minor bones. This is intended to get at the fundamental or root causes of the problem. Other people do not include this level of detail on their fishbone diagrams.

When you are done, look at the entire diagram. Does it have reasonable balance across the major bones? Are any common themes emerging? Can you identify causes that are measurable and fixable and which you believe are likely to have a large impact on the problem?

In some situations, you may find that a flow diagram of the work process may be more valuable and informative.

Further reading

1. The Memory Jogger, A Pocket Guide of Tools for Continuous Improvement. Brassard, M. (1988) Methuen, MA: GOAL/QPC.
2. Basic Tools for Process Improvement: Cause-and-Effect Diagram [PDF] Description: This website offers simple explanations of the cause and effect diagram, a classic tool used in quality improvement. This same guide is also found at www.management-tools.org/files/c-ediag.pdf and www.saferpak.com/cause_effect_articles/howto_cause_effect.pdf. Other guides are available at www.hq.navy.mil/RBA/text/tools.html.

07/14/2008. Category: Quality control