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Fishbone Analysis is the process of finding the fundamental reason why some event or defect occurred through use of the Ishikawa or fishbone diagram. The reason people are interested in such a process is that identification of the reason for an event increases the chance that the event can be caused or prevented in the future.
There are many tools that have been created in order to perform root cause analysis. Some of these tools are the Pareto chart, failure mode and effects analysis (FMEA), and the fishbone diagram. While all of these tools are useful, the fishbone diagram will be looked at more closely.
The fishbone diagram has few other names such as the cause and effect diagram, 5-Whys, and the why-why diagram. These names are appropriate because this tool seeks to find the reasons why a particular event (the effect) was caused.
The general algorithm for completing the fishbone analysis is to begin by identifying the effect and working backwards. Typically this is the event or defect for which one is trying to determine the cause. The next step in the process is to identify the cause of that effect. This is often accomplished by asking the question, "Why did this effect happen?" Several different answers may be generated and such a list should be anticipated. Once these answers are discovered, you ask the question, "Why did this cause happen?" for each of the causes generated in the previous step.
The "why" question is asked for each cause until no further answers can be generated or until 5 generations have been completed (hence the 5-Whys). As a result, the general shape of this diagram resembles a horizontal tree. The original event (the effect) is listed at the far right. A horizontal line is then drawn to the left. Off of this horizontal line, the answers to the "why" questions are listed. Reasons for those answers are then listed branching off. In many cases, the branches are slightly slanted which creates a fishbone look.
An example of the 5-why chain for a company which has just lost a customer follows. The company lost its customer because the price was too high. The price was too high because the assembly process took longer than it should have. The assembly took too long because the workers didn't have the correct tools. They didn't have the correct tools because the tools weren't ordered. The tools weren't ordered because upper management was hoping to cut costs for the quarter.
Once the root cause has been exposed, steps can be taken either to ensure that root cause will be avoided the next time if the end effect was negative, or that it happens again if the effect was positive. If the root of a problem is not properly identified, only the symptoms of the problem are treated rather than the cause itself. Such practices can lead to excessive costs, reduced quality, slow delivery, or all three.
Daiv Russell is a marketing and management consultant with Envision Web Marketing. Learn more about the Fishbone Diagram, and Root Cause analysis as well as other Project Management resources.
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