Cause and Effect Diagram
This, one of the seven basic quality tools, was invented by Dr. Kauro Ishikawa of Japan. Therefore it is also called Ishikawa Diagram. Owing to its similarity to the fish skeleton, it is popularly called ‘Fish Bone’ Diagram. As the name suggests, this quality tool shows relationship between an effect, represented by an arrow and their cause/s by the fins. It helps in identifying, sorting, and displaying causes of a problem or quality characteristics graphically.
Where to Use: This technique is used to find the root cause in case of complaints, rejections, accidents, and administrative issues. Based on the symptoms, the root cause can be traced.
How to Use: The creation of a Cause and Effect Diagram is simple. A broad arrow is drawn from left hand side aiming towards the right hand side. The problem to be investigated is written at the tip of the arrow.
Now consider possible variables that might have caused the problem or the defect, broadly categorized under following heads:
Assign one fin of the arrow to each of the stated causes. These causes can further be divided into sub-causes, if required, until root cause is found. In some cases, the root cause may be simple to reach at, while other may require digging into sub-causes and sub-sub-causes. In such cases, each major cause may be considered as a single problem and then reach to the root cause.
Benefits: The cause and effect diagram helps in identification of root cause of problem by presenting a very broad view of the situation. Everyone involved in investigation gets a clear cut understanding of the subject of discussion and rationale behind it. Thus by unifying the thoughts of investigating team it becomes simpler, time saving and point specific to analyse the problem, and solve it.