A fishbone diagram, also known as cause & effect diagram, is a visualization tool which categorizes potential causes of a problem to identify its root cause. Many a times employees try to resolve problems but they end up working over the symptoms instead of the root cause. This tool helps employees avoid solutions that merely addresses the symptoms of much larger problems.
It is used during brainstorming sessions to plot all the possible causes of a problem, which later are ranked as per their level of importance in a diagram form. The diagram looks like a fish skeleton, where large bone branches out smaller bones which contains more details.
If we discuss its role in Six-Sigma, fishbone diagrams are used during the “analyse” phase of DMAIC approach to dig to the root cause of a problem. It makes the brainstorming sessions productive. Frequently it is observed that such sessions don’t bring out useful ideas or information, but using the fishbone diagram tool with it translates it into a well-structured form and unveils unobvious potential causes.
How is this diagram prepared? The central problem or effect is paced on the extreme right of the diagram & a horizontal arrow is drawn running to it. Categories of causes are written as branches from the main arrow. All the possible causes of the problem are written as a branch from the relevant category. Causes are given branches which then mentions sub-causes. “Why?” is continued to be asked to find deeper level of causes.
