Cause-and-effect analysis or Ishakawa diagram is a graphical approach to failure analysis. It is also referred to as fishbone analysis, a name derived from the fish-shaped pattern that is used to plot the relationship between various factors that contribute to a specific event. Typically, a fishbone analysis plots four major classifications of potential causes (i.e., man, machine, material, and methods), but can include any combination of categories.
Like most of the failure-analysis methods, this approach relies on a logical evaluation of actions or changes that lead to a specific event, such as machine failure. The only difference between this approach and other methods is the use of the fish-shaped graph to plot the cause-effect relationship between specific actions, or changes, and the end result or event.
This approach has one serious limitation. The fishbone graph does not provide a clear sequence of events that leads to failure. Instead, it displays all of the possible causes that may have contributed to the event. While this is useful, it does not isolate the specific factors that caused the event. Other approaches provide the means to isolate specific changes, omissions, or actions that caused the failure, release, accident, or other event being investigated.