The Ishikawa diagram is a graphical method for finding the most likely causes for an undesired effect. The method was first used by Kaoru Ishikawa is the 1960s.
Because of its shape, it is also known as the fishbone diagram. Other names for this technique are: the cause-and-effect diagram or root cause analysis.
How to make the diagram
Take a sheet of paper and draw a box on the right side of the paper. Draw a horizontal line from the left side of the box to the right. Write in the box the effect for which you want to find the causes. Starting from the horizontal line, draw four to six short diagonal lines in the direction the left upper and left lower corner of the paper. These are the main bones of the diagram. Label them with categories you know will span the whole problem space. For example, a business may use: management, manpower, machines and materials (the 4 M's).
Next, start filling the diagram with causes. Put them as arrows pointing to any of the main bones of the diagram. After you feel you have named most causes, identify the most likely causes for the effect in the box on the right side.
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