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Cause & Effect

What is a Cause & Effect Diagram

Also known as fishbone, C&E, Ishikawa diagram

Fishbone shaped diagram with Effect (Y, output) being the head and Bones as the major causes (Xs). This is about cause and effect and not symptoms

  • It can have a fair amount of detail in a visual format, which is easy to read and relate to. 

  • Removes personal biases - a team tool

  • Keeps focus on the problem

Fish bone sample.png
When to use Cause & Effect Diagram
  • To arrive at a root cause

  • Focus on causes and not symptoms

  • To brainstorm & visually present, the output of a brainstorming session

How to make a Cause & Effect Diagram
  • The tool involves brainstorming - so the rules apply

  • Place the problem statement on the right side of the board, vertically in the middle

  • Now, either ask the team for major cause areas or use 

  • 6 Ms: Man, Machine, Method, Mother Nature, Material & Measurement - remove any that don't apply

  • Major process steps 

  • Use regions (increase sales problem)

  • previously collected data to write bones and get consensus

  • So now you have the head and major bones  

  • Let's brainstorm on causes related to each bone

  • Drill down further into each sub cause - ask "why", ask "what causes it" "why does this happen" - this may then be placed a sub bone

  • This goes on, until either you start going out of your control area  or team can't answer any more

  • Once completed

  • look for causes that appear repeatedly

  • you can highlight the prominent ones and get them voted upon to prioritize

  • do confirm the frequency of causes, if low, their impact on the problem may also be low 

Variations of Cause & Effect Diagram
  • CEDAC - Cause and Effect with Addition of Cards

Example of Cause & Effect Diagram
  • The head is why low core production hours 

  • Major bones are based on 6 Ms

  • This example only shows till level 2 causes , you can create further bones by adding  a vertical / slanting arrow to the sub bone

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