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The Last Step to 5 Whys Process – The “So What?” Test

By Ron Pereira Updated on May 17th, 2017

The 5 Whys Process is an extremely powerful root cause analysis technique when applied properly.

As we explained in our recent Gemba Glossary video focused on the 5 Why there are situations where asking why a few times will suffice while other situations may require more in depth questioning that could lead to several “branches” of why questions.

With this said, one technique I strongly encourage all lean and six sigma practitioners to practice is what we call the “So what?” test.

Steps to the So What Process

Once you and your team, since the 5 Why Process is best done with a team, believe you have identified a root cause worthy of further investigation the “so what” test can done as follows.

  1. Starting at the bottom, with the last statement, read it out loud and end the sentence with the word “so…”
  2. You then read the next statement to make sure it makes sense while ending that statement with the word “so…”
  3. Repeat these steps until you reach the top statement in the analysis

Spoiled Milk Example

Let’s go ahead and use the same spoiled milk example we introduced in the Gemba Glossary: The 5 Whys video.

In that example our 5 Whys analysis (4 whys were asked in this example) resulted in the following.

Problem: The Milk is Spoiled

  1. Q: Why is the milk spoiled? A: We didn’t drink all the milk cartons before expiration.
  2. Q: Why didn’t we drink all the milk cartons before expiration? A: We had too many cartons in the fridge.
  3. Q: Why did we have too many cartons in the fridge? A: We bought more cartons than we needed.
  4. Q: Why did we buy more cartons than we needed? A: There was a sale on milk and we tried to save money.

Ask So What?

To practice the “so what?” test all we need to do is work backwards stating “so” at the end of each statement. Let’s see what this looks like.

  1. There was a sale on milk and we tried to save money, so…
  2. We bought more cartons than we needed, so…
  3. We had too many cartons in the fridge, so…
  4. We didn’t drink all the milk cartons before expiration, so…
  5. The milk is spoiled.

Just Common Sense?

Now, as simple as this is, some may think it’s a waste of time to ask so what… it’s not. You’ll be amazed how many times things don’t make sense when adding “so…” to the end of each statement like this thus identifying a need to re-examine your 5 why analysis.

What do you think?

Have you ever tried this approach? If so, how has it worked out? Do you have another technique for checking the results of your 5 why analysis before attempting to apply a countermeasure? If so, how do you go about this?


  1. Daniel Stoelb

    September 28, 2011 - 11:41 am

    My company actually does it by asking therefore but so seems a bit easier so we’ll try that next time since using techniques like this really does help.

    Ultimately the only read way to validate things is to attempt to correct the situation using what you learned.

    I have seen consultants who warn about how hard 5 Why is only to psyche people out before they start. Sure, it’s not easy but it can be done effectively with a little practice and patience.

    • Ron Pereira

      September 28, 2011 - 12:35 pm

      Thanks, Daniel. Yes, it does take practice and I agree that validation through the application of a countermeasure(s) is the ultimate way to confirm the analysis.

  2. Mark Graban

    September 28, 2011 - 12:01 pm

    Great post, Ron! This is a very powerful question… “so what? or “what is the impact of that problem or change?”

    • Ron Pereira

      September 28, 2011 - 12:33 pm

      Thanks, Mark. Let’s grab coffee soon.

  3. james Lawther

    September 29, 2011 - 3:36 pm

    Interesting post Ron, I like the way running back up the chain stress tests it.

    The problem I have though is that people either stop asking why too soon (we had too many cartons in the fridge, solution buy a smaller fridge) or too late (why was there a milk sale on?)

    What phrase could I use to make sure people had got to the point at which the analysis is useful, rather than just asking why 5 times?


  4. Matt Nelson

    October 20, 2011 - 7:12 am

    This is a great example of one of the “commandments” of LEAN and/or Improvement – “Go fo rthe simple solution and use your wits, not the wallet”.

    In my experience, I have seen many teams jump in to the newest tool, complex software number cruncher, etc….. when the best and most powerful thing they can do is just start asking questions of the process.

    Great post!

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