What Is a Bonefish Diagram?

By on Sep 9, 2013 in education | 18 comments

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What Is a Bonefish Diagram?

Cause and effect

English: French toast served at Mac's Restaura...
French toast served at Mac’s Restaurant in Rochester, Minnesota. (Photo credit: Wikipedia)

In 1968, a Japanese statistician, Kaoru Ishikawa, invented a diagram to simplify finding the cause of problems.

It has been called an Ishikawa diagram, after its inventor, and a bonefish or fishbone diagram for its shape, and a root cause analysis diagram, for its purpose.

Let’s suppose that you are making French toast, but it is coming out too soggy and you want to figure out why.

We’ll cut down a recipe from SimplyRecipes.com for this activity.



But, this is how you make perfect French toast. What if it is soggy? Why might that be?

Let’s draw a bonefish diagram to see if we can isolate the possible cause of soggy French toast.

First, draw a line across the middle of a page turned long-wise.

Draw the outline of a fish head at the right end and inside the head, write: Soggy French bread

Draw two lines at an angle to the left off the top of the center line and two lines at an angle to the left off the bottom of the line, so that all lines off the center are at the same angle above and below the line.

The reason this is called a bonefish diagram is that the angled lines off the center line look like fish bones.

On the four lines, write possible factors that might affect how French toast turns out: Environment, People, Materials, Tools.

Along the line for Environment, draw lines with possible reasons the environment might affect how the French toast turns out.

For example, the temperature of the skillet might affect whether the French toast turns out soggy.

It might be too hot or too cold, so draw a line off the Environment line and label it Skillet temperature, then draw two lines off the Skillet temperature line and label them, Too hot and Too cold.

Similarly, think of reasons for the other factors that might affect the French toast.

For people, you might have no experience in making French toast, so you don’t know what it is supposed to look like when it is done, or two people might be making it together and not coordinating when the bread is soaked and when the skillet is hot, so draw two lines off the People line and label them Inexperienced Cook and Cooks Not Communicating.

For Materials, the butter used to cook the French toast might burn at a temperature when it is hot enough to brown it correctly, or you might have added too much milk for the number of eggs used, so label two lines off Materials Butter burns and Too much milk.

For Tools, the skillet may be old and may not heat up evenly anymore, or the stove may not get hot enough, so label two lines off Tools as Old skillet and Stove not hot enough.

Ishikawa designed this method of problem-solving because once individual factors involved in a problem can be isolated, it is easier to find the one that is the cause.

If it is not apparent at this point why your French toast was soggy, then you can change one factor at a time to test which one is causing the problem.

Why Is This Useful?

Initially, this diagramming technique was used to identify problems in shipbuilding.

Mazda used it in car manufacturing for the Miata sports car, identifying factors to achieve what they called, Horse and Rider As One, that included such details as putting the armrest at the right height on the driver’s door so that you could put your elbow on it.

From there, it moved out into the larger business world as a general problem-solving tool in sales and marketing, as well as manufacturing and service businesses.

teacher uses it to introduce her students to appropriate behavior in the classroom, isolating behaviors that are disruptive and identifying those that make for a successful learning environment.

Thanks to the book, Thinking Tools for Kids: An Activity Book for Classroom Learning, for the French toast activity.


Carol Covin, Granny-Guru

Author, “Who Gets to Name Grandma? The Wisdom of Mothers and Grandmothers”