Fishbone/Ishikawa Diagram
Fishbone diagrams, also known as Ishikawa diagrams or cause-and-effect diagrams, are graphical tools for root cause analysis. The objective of using a fishbone diagram is to identify potential causes of a problem or effect and categorize them in a structured manner. This assists teams in understanding the origins of a problem, facilitating a comprehensive analysis before moving towards solution implementation. This technique aligns well with the concept of Requirements Life Cycle Management in business analysis, where understanding the problem deeply can lead to effective requirements elicitation and management.
Key Components of Fishbone Diagrams
Head (Effect/Problem): The specific problem or effect under analysis is stated at the "head" of the fishbone diagram. It is often framed as a question.
Spine (Central Axis): A horizontal line that extends from the head and serves as the backbone of the fish. This line is where the primary "bones" or categories of causes are attached.
Bones (Causes and Categories): Major categories of causes or factors that contribute to the problem. These "bones" branch off from the spine. Each category may further have sub-categories or "sub-bones," which are the sub-causes contributing to the primary cause.
Sub-Causes: These are finer-level causes that stem from the primary causes. They are also branching off as smaller "bones" from the primary bones on the diagram.
Process for Creating Fishbone Diagrams
Define the Problem: Clearly articulate the problem or effect that you want to analyze and place it at the head of the fish.
Identify Categories: Use standard categories such as machines, methods, materials, measurements, people, policies, processes, and places, or customize based on the specific context.
Identify Causes: For each category, brainstorm possible causes contributing to the problem. Place these along the "bones" of the diagram.
Identify Sub-Causes: Dig deeper into each primary cause by asking “why” it happens, and identify sub-causes. Continue this process to create multiple layers of sub-causes as needed.
Analyze and Prioritize: Look for patterns among the causes. Mark or circle those that seem to be more significant or recurring, as these may be the root causes requiring focused attention.
Limitations and Considerations
While fishbone diagrams are powerful for initial root cause analysis and facilitate a structured brainstorming process, they are not exhaustive. They serve as a starting point and may need to be complemented by other techniques like Five Whys, surveys, or data analytics for a comprehensive analysis.
Overall, the use of fishbone diagrams enhances the quality of requirements and solutions by ensuring that teams do not jump to conclusions but rather engage in a thorough analysis to understand the underlying issues contributing to a problem.