An Ishikawa diagram is a tool that the project team should use to find the cause of the defects associated with project deliverables. An Ishikawa diagram, also known as a fishbone diagram or a cause-and-effect diagram, is a graphical tool that shows the possible causes of a problem or effect using a fishbone-like structure. An Ishikawa diagram can help to identify and analyze the root causes of defects or issues and find solutions to prevent or eliminate them.