5 Whys

The “5 Whys” is an iterative problem-solving approach to manufacturing issues. It was developed by Taiichi Ohno as a part of the Toyota Production System, and is closely related to Root Cause Analysis and Six Sigma.

Key Takeaways

  • Minimalist approach to root cause analysis

  • Used alongside fishbone diagram, DMAIC approach, Six Sigma

  • End goal should be a process in need of improvement

What Are The 5 Whys?

The “Whys” of 5 Whys are the exact same question: why?

That may sound confusing, but it’s really because these 5 questions aren’t different at all, it’s just the same question being repeated. This is because you’re not trying to dig wider, but deeper.

The 5 Whys are a brainstorming exercise that assists in root cause analysis, or figuring out the base causes that are affecting a problem later throughout a process.

Example of 5 Whys As A Problem-Solving Tool

The 5 Whys can be used to dig deeper into almost any basic problem you have within a manufacturing context. Here’s just one example of how asking Why repeatedly can lead to insights about the root cause of a problem:

Why #1: Our manufacturing job order was canceled
Why #2: We didn’t have the finished product ready in time
Why #3: The required material components we needed arrived late
Why #4: Our parts supplier misinterpreted our order request
Why #5: Our supply chain system is not streamlined and user-friendly

The Purpose of 5 Whys in Manufacturing

The final answer – the root cause of the problem – should lead to a process.

It’s not exactly helpful to just end up with a collection of problems or issues, because you won’t know where to start to begin correcting things.

It’s also not helpful to ask Why 5 times only to end up with an answer that is something you can’t control, like a different part breaking in a piece of machinery.

Processes are things you can change, and that have the most effect overall in making a difference. By tweaking a process for improvement, you can attain a more dependable quality workflow with fewer defects.

Complementary Tools To Use With 5 Whys

5 Whys is a lean tool that is intended to be basic so that details aren’t missed by jumping to conclusions and hypotheses.

You can supercharge the benefits of using 5 Whys by combining it with other lean tools commonly used in modern manufacturing:

Fishbone (Ishikawa) Diagram

The Fishbone, or Ishikawa Diagram, was another popular tool used in the Toyota Production System around the same time as the 5 Whys. It’s very similar to the 5 Whys because it also dives deeper into root cause analysis.

However, it’s different because the Fishbone diagram includes many other “branches” – or in this case, “fishbones” – that fan out from the main problems or causes of the issue.

This is a good complementary tool to use with 5 Whys when there are many separate potential problems (each with its own root causes) inherent in a process.

The Six Sigma Approach

The DMAIC approach is a Lean Six Sigma technique that stands for the following actions: Define, Measure, Analyze, Improve, Control. It is also a type of root cause analysis used in manufacturing.

To be specific, the 5 Whys can fit within the “Analyze” section of the approach, where you question and research the potential reasons for an effect.

Using the DMAIC approach is especially helpful when you want to link a finished 5 Whys analysis to a greater plan for correcting a failed process.

What Are The Five Steps of Root Cause Analysis?

The 5 steps of root cause analysis are the same question: Why. It’s important to repeat this step five separate times because each iteration delves deeper into the potential solution which addresses the root cause.

Do You Need All 5 Whys?

It’s important to repeat the Why question five times because problems that cause issues in production are rarely surface-level. You may stumble across a root cause after the first Why, but if you stop there then you will miss other, deeper issues that contribute to that root cause.

After all, manufacturing operations are complex and involve many moving parts. By being diligent in uncovering problems, there is a higher chance of solving those problems once and for all.

What Is A 3-Legged 5 Why?

A 3-legged 5 Why diagram is a more detailed version of the original 5 Whys process that repeats three times, each addressing a different area of root cause analysis:

  1. The first leg asks why about process-specific issues
  2. The second leg asks why the problems weren’t detected earlier
  3. The third leg asks why issues are systemic to the organization

These 3 legs of the 5 Whys are separated to uncover several different factors that are a part of root cause analysis simultaneously. This means it is a very thorough version of process correction.

Using a 5 Whys Template For Root Cause Analysis

You don’t need anything fancy to get going with using the 5 Whys. However, you may not know where to start since it’s a very minimalist exercise, so feel free to use the our 5 Whys template below:

5 Whys Template for Root Cause Analysis

Begin by filling out the top left hand section labeled “Why #1”. This should be a short description of the specific problem you are trying to solve. From there, ask yourself why that first problem is occurring, then write the answer in the box labeled “Why #2”. Continue this process until you reach the Fifth Why, or the root cause of the original problem.

For a 3-legged 5 Why exercise, use three copies of the above diagram and use one to analyze processes, another to analyze detection protocol, and the third to analyze systemic concerns.

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