Five Whys Analysis

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Root cause analysis (RCA) is an essential part of maintenance and safety processes. There are several different methods to perform a root cause analysis, some more in-depth than others. For small issues that don’t require a root cause analysis that digs deep, you can use the Five Whys analysis. The Five Whys analysis is a simple root cause analysis method that involves asking why at least five times. This method originated at the Toyota Motor Corporation, where the founder, Sakichi Toyoda, encouraged employees to ask why five times to get to the root of any problem. As an RCA method, it involves a much smaller investment of time and resources to complete.

How to Use Five Whys Analysis

The objective of root cause analysis is to get past the easy-to-see surface-level cause. Five Whys is a great place to start and get your mind thinking about the root cause.

Here’s how it goes:

  1. Why did X happen? Because of Y.
  2. Why did Y happen? Because of W.
  3. Why did W happen? Because of V.
  4. Why did V happen? Because of R.
  5. Why did R happen? Because of Z.

Your answer to the previous question is what creates the next question. In this example, Z may be your root cause of the problem, or you may find that you can go further. You’re not limited to only five levels, and there is no guarantee that the fifth answer is your root cause every time. The objective of Five Whys is really to get you past the first obstacle of thinking deeper and analyzing past the surface. And, of course, your root cause analysis is not complete without a plan to prevent the root cause. The final steps are to implement your plan and review or inspect it regularly to ensure that it is working.

Additionally, you’re not limited to only using one root cause analysis method. Five Whys could be where you begin to get some ideas, then go deeper with other more comprehensive methods. Using the Five Whys method is best for simpler problems, as it focuses on a single line of cause. If you just want to explore the cause of a non-critical issue like a breakdown in process or human factors, then Five Whys is great to use.

The Benefits of Five Whys

As illustrated above, Five Whys is an excellent method to start your root cause analysis. It has many benefits, including:

  • A very cost-effective RCA method
  • An easy process to implement and follow
  • Doesn’t require software, tools, or diagrams
  • Inspires thinking past surface causes
  • Simple enough to apply to small problems that don’t require a more complex RCA method

While Five Whys has its benefits, it also comes with some restrictions to consider. Five Whys is limited to the knowledge of your team. So, if the root cause is something that requires research to discover, then Five Whys won’t find it. That’s why it is best to consider alternative methods for more complex problems.

Root Cause Analysis for Any Situation

You can combine Five Whys analysis with other root cause analysis methods. Fault tree analysis takes Five Whys and branches out to explore multiple possible causes linked to the same event. Also, Five Whys works well paired with Failure Mode and Effect Analysis (FMEA). FMEA is a proactive version of root cause analysis that asks, “What could go wrong?” in an attempt to predict potential process or equipment failures. FMEA can offer great insight for your Five Whys analysis when you are facing a problem. At the end of the day, all of these methods are to encourage failure prevention. Regardless of the method you choose, your focus should be on finding the cause and creating a plan to stop it.

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