Fishbone Diagram – Fishbone Analysis

What is a Fishbone diagram and Fishbone Analysis?

Fishbone diagram is an analysis tool to provide systematic way of understanding effects and the causes that create those effects. The design of the diagram looks like the skeleton of a fish, hence it is referred to as the fishbone diagram.

Dr. Kaoru Ishikawa, a Japanese quality control statistician, invented the fishbone diagram. Also referred to as the Ishikawa diagram. Also it is referred to as a cause-and-effect diagram.

It provides a great value in assisting teams in categorizing the many potential causes of problems or issues in a systematic way and helps identifying root causes.

Fishbone diagram can be used when:

  • The team needs to study a problem to determine the root cause
  • Want to study all the possible reasons why a process is having difficulties, problems, or breakdowns in the initial stages of the process.
  • Need to identify areas for data collection
  • To study why a process is not performing properly and/or producing the expected results

Creating a Fishbone Diagram

  1. Draw a fishbone diagram
  2. List the problem/issue to be studied in the head of the fish
  3. Label each bone of the fish. The major categories typically used are:
    • The 6 M’s: Methods, Machines, Materials, Manpower, Measurement, Management
    • The 4 P’s: Place, Procedure, People, Policies
    • The 4 S’s: Surroundings, Suppliers, Systems, Skills
  4. Repeat this procedure with each factor under the category to produce sub-factors. Continue asking, “Why is this happening?” and put additional segments each factor and subsequently under each sub-factor.
  5. Continue until you no longer get useful information as you ask, “Why is that happening?”
  6. Analyze the results of the fishbone after team members agree that an adequate amount of detail has been provided under each major category. Do this by looking for those items that appear in more than one category. These become the ‘most likely causes”.
  7. For those items identified as the “most likely causes”, the team should reach consensus on listing those items in priority order with the first item being the most probable” cause.

FishBone-Diagram-6Ms-(Man-machine-management-measurement-material-method)

FishBone-Diagram-4Ss-Surroundings-Suppliers-Systems-Skills

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