What is a fishbone diagram?

  • Fishbone imageFishbone diagrams are used to identify the key Causes (Xs) that influence the output measure (Y).
  • The major categories are used to direct the team in asking “Why?” until actionable inputs of the effect are identified.
  • The categories ensure that all inputs are considered, e.g. not just milk (a material) but also its temperature (a measure) and the milk jug (equipment).  By just using the process map and brainstorming, some of these inputs might be overlooked.

The Fishbone Diagram has a number of categories to consider and might stimulate ideas about inputs missed during brainstorming. It is a tool that helps the team think of potential root causes to the problem from a number of different perspectives.

The tool encourages teams to look at multiple categories of inputs to discover the  root cause(s). It helps reach a common understanding of potential causes and exposes gaps in existing knowledge.

Description of problemSTEP 1: Draw a box on the far right-hand side of the paper with a horizontal arrow to the box and write the description of the problem in the box.

It is critical for the team to agree upon the problem under study. In most cases, the problem will be identical to the definition of Y.

Fishbone imageSTEP 2: As a team, come to consensus on the 4-5 major cause categories to use on the fishbone diagram. Write the names of the major cause categories above and below the horizontal line. Connect them to the “back bone” of the fish.

Typical cause categories include:

    • Machines (equipment)
    • Methods/procedures (how work is done/tasks and steps)
    • Materials (components or raw materials)
    • People (the human element)
    • Mother Nature (Environment)
    • Measurement (data collection)
    • Policies (higher level decision rules)

step 3STEP 3: Brainstorm a list of possible causes that could be driving the problem.

Brainstorming can be done by category or can be done prior to placing the potential causes on the major bones. It is recommended that the entire list of possible causes be generated first before attempting to place them on the major category bones. This keeps the creative flow of ideas.

Fishbone Diagram Step 4 and 5STEP 4: Place the brainstormed data causes in the appropriate cause category.

STEP 5: For each cause, drill down into “causes of the causes” by asking repeatedly, “why does this happen?” Arrange contributing causes on the smaller bones.

About Training Leadership Consulting

Training Leadership Consulting (TLC) is a leading Business Improvement Service Provider. Founded in 2001, TLC provides Training and Management Consulting services focused on Process Management and Performance Improvement. Your company will benefit from TLC's years of International and local experience in Change Management, Process, Lean and Six Sigma. View their website www.tlc-global.com
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