#4 – 2 Reasons to Do a Cause & Effect Diagram

The #4 Classic Lean Leadership post is a tool commonly used in Lean Six Sigma problem solving. That tool is the Cause & Effect (aka Fishbone) Diagram. You’ll notice that the illustration is a hand drawn C&E on a white board. I chose this illustration because I am a big fan of practical problem solving. Here is #4 on the list:

A hand drawn Cause & Effect Diagram

The Fishbone diagram is also known as the Cause & Effect (C & E) diagram or as the Ishikawa diagram referring to its originator, Professor Kaoru Ishikawa.  The C & E diagram is a good tool when you need to identify the root cause of a problem.  It is also a good tool when there are several possible causes to explore.  Using the Ishikawa diagram enables you to brainstorm and collect possible causes in a group setting.

The mechanics of a Fishbone diagram are not too difficult:

1. Identify the problem.  Be careful to keep the scope small and manageable.   Using the Pareto Principle is a great way to narrow the scope.
2. Write a problem statement on a dry-erase board or flip chart.  Draw a box or circle around this statement.
3. Draw the main bones of the diagram.
4. Label the bones.  The categories are easier to remember if you call it 4 ME:  Man (People), Machine (Equipment), Method (Procedures), Materials, Environment. See below for more on the 4 ME.
5. Brainstorm causes and record them on the bones (see diagram).  Capture the causes and avoid solutions at this point.  “Poor Quality Raw Ingredients” is better than “Need a new vendor.”
6. Identify which causes are most likely to cause the problem and to have the biggest impact.  Validate that there is a true cause and effect with these conditions.
7. Perform a Root Cause Analysis for the leading causes.  Some people like to do the 5 Why RCA right on the Fishbone diagram.  Pete Abilla shows how you can do this at shmula.com.  This works with a simple 5 Why but you might find it difficult if it turns into a complex multiple path 5 Why.
8. Identify and implement countermeasures.

More detail about the 4 ME catagories:

• Man (People) – anyone involved in the process and contributes to the undesired effect.  Names are not needed.  Capture the contributing factors such as not following SOP’s.
• Machine – equipment, computers, tools, etc.
• Materials – consumable supplies, packing or raw ingredients, etc.
• Methods – policies, procedures, common practices
• Environment – time, temperature, company culture, etc.
• Some people also use Management, Measurement, and Maintenance.

Two watch outs when doing an Ishikawa diagram:

• Keep you scope small.  You can get what Jay Arthur calls a whalebone in Lean Six Sigma Demystified if you are not careful.
• Don’t spend too much time debating where to place a particular cause.  It won’t matter as much as finding the right countermeasure.

You can solve a lot of issues using a few of the right tools.  Pareto charts, Fishbone diagrams, and the 5 Why Root Cause Analysis work very well together to prioritize, identify, and resolve issues.  What can you solve using these tools today?
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