October 2, 2019 | Mark Paradies

5-Whys Example – Is this Root Cause Analysis? (Updated)

Most Famous Example of 5-Whys

Taiichi Ohno (pictured above), created the 5-Why technique. He is quoted using the following 5-Why example to teach the technique:

1. “Why did the robot stop?”

The circuit has overloaded, causing a fuse to blow.

2. “Why is the circuit overloaded?”

There was insufficient lubrication on the bearings, so they locked up.

3. “Why was there insufficient lubrication on the bearings?”

The oil pump on the robot is not circulating sufficient oil.

4. “Why is the pump not circulating sufficient oil?”

The pump intake is clogged with metal shavings.

5. “Why is the intake clogged with metal shavings?”

Because there is no filter on the pump.

This is the inventor of the technique and his most famous 5-Why example. If the inventor of 5-Whys uses this 5-Why example, certainly this is a “good” example of how 5-Whys works. And “No Filter” is his root cause (the fifth why).

Is “No Filter” a Root Cause?

I would never call “NO FILTER ON THE PUMP” a root cause. Would you?

This 5-Why example isn’t abnormal. It is typical of many of the 5-Why examples I have seen people struggle to complete. (Examples HERE)

Struggle? Isn’t 5-Whys suppose to be easy?

It is easy … But it is ONLY easy if you already know the answer BEFORE you start asking why.

I had a relative who works in a factory. The boss was taught 5-Whys. When something goes wrong, he starts asking. “Why.” The worker says that if they knew “Why” they would fix it or they would not have the problem to start with. So, they make up answers to his why questions because they know he won’t stop asking why until he gets to five. They try to think of answers where no one will be blamed. The worker says they usually figure that they will just be more careful.

What do you think of 5-Whys? Let me know your thoughts below…

And that brings us to several limitations or drawbacks of using 5-Whys…

5-Why Drawback 1: Confirmation Bias

What is “Confirmation Bias?”

The term was developed by researchers to highlight a problem with the scientific method. When someone thinks they “know” the answer, they preferentially look for evidence that confirms their answer. Thus, they have a confirmation bias.

Because 5-Whys is easy when you “know” the answer … 5-Whys frequently suffers from confirmation bias (the investigator naturally looks for evidence that makes their 5-Why chain work and ignores evidence that is counter to their beliefs). Frankly, if you know the answer, why look for evidence at all!

Thus when asking why, the investigator finds the answer they started out to prove.

For more reading about Confirmation Bias, see:

5-Why Drawback 2: Focus on a Single Root Cause

If you follow a single 5-Why questioning chain you only get one root cause. Just like Taiichi Ohno did.

But is there just one root cause for the robot example?

In another analysis of this example using the TapRooT® System, we found four Causal Factors. Each Causal Factor has at least one root cause and maybe more. That means that Taiichi Ohno missed at least three root causes. To see the comparison of Taiichi’s example and the TapRooT® Analysis, go to:


Failure to consider multiple root causes is a common problem when using 5-Whys. Have a look at the example in this professional society magazine (the bugs example – click on the cover below).

5-Why Drawback 3: No Guidance to Find the Causes of Human Errors

5-Whys often stops at “human error” as a root cause. But as we explained in this article:

Human error is NOT a root cause.

Most people investigating problems have no training in human factors (the science of human error). That’s why we included human error analysis guidance in the TapRooT® System. You can see how some of the embedded intelligence in the TapRooT® System works if you read the article referenced above.

Are You Dissatisfied with 5-Why Root Cause Analysis?

We don’t find that surprising that you find 5-Whys lacking. The three drawbacks listed above are just some of the reasons why 5-Why analysis is usually insufficient to find root causes. Even smart, well-trained users (Like Taiichi, himself) frequently jump to conclusions, follow a single root cause trail, and fail to adequately analyze the causes of human error. That’s why 5-Why examples like the one above (the robot example) aren’t rare.

Perhaps it is time you discovered the fundamentals of root cause analysis and learned an advanced root cause analysis system – TapRooT®!

Learn More About TapRooT® Advanced Root Cause Analysis

You can have TapRooT® Training at your site or attend one of our public TapRooT® Courses to learn more about advanced root cause analysis.

To have a TapRooT® Root Cause Analysis Course at your site, CONTACT US for a quote.

Or attend one of our public TapRooT® Courses at the locations and dates listed at this link in the menu above.

Don’t wait! Register today so you can start saving lives, prevent injuries, improve product quality, stop equipment failures, and improve production by using advanced root cause analysis.

Operational Excellence, Quality, Root Cause Analysis, Root Cause Analysis Tips
Show Comments

79 Replies to “5-Whys Example – Is this Root Cause Analysis? (Updated)”

  • Mark Paradies says:

    Hi Joestein

    Thanks for your comment and this is where I started out almost 30 years ago. I was wrong then, realized it, and put the work in to develop a first cut on the model that people needed.

    Many engineers think that technical competence is the key. But many solutions lie outside the arena of technical competence. They are human factors solutions to human error problems. This is knowledge that many engineers never learn.

    People can be led to solutions they have never considered before. I see it every time we teach a course. Quite amazing.

    Attitude and competency are important. However, they aren’t the solution. The right root cause analysis system (TapRooT�) + attitude + competency + management support is the key.

    Hope you make it to a course some day so you can see what you are missing.



    Often many prefer the 5Why linear method and shy away from the horizontal method due to it being time consuming but fail to realize that the impact on the outcome of a 5why could be detrimental to a process as it may just address the symptom and not the cause.

    The 5WHY Horizontal Method Based on the Effects from the 4M’s works well.
    This method tends to allows for a broader insight to the possible causes so that other areas of the process are addressed whilst identifying the root cause thus satisfying the baseline for the RCA, the 80-20 rule.

  • Sean says:

    Hi all, I have read the above comments and i am of a slightly different opinion, I believe the 5 why and how process is a tool to get people think differently from the norm. It is not a absolute for finding RCA but will start a body of people to “begin” to crete a new culture.

    In short it’s a start of a journey for people think differently and this is simple and easy way to start.

  • Ken Reed says:

    Hi, Sean.
    Thanks for your comment
    5-whys may start you thinking in a slightly different direction. Unfortunately, it only gets you thinking in a direction you are already familiar with. It does not get you thinking outside your normal experience. For example, when someone from the Training Department conducts a 5-why, amazingly enough, their root causes come up as “the person did not receive the proper training.” If the investigator is not familiar with human engineering or ergonomics, they will never ask any 5-why questions that lead them to possible problems in those areas.

    Additionally, most people do not use 5-why’s as only a starting point. They use it as their final method of finding a root cause. with the severe limitations inherent in the methodology, it rarely gets to actual root causes, yet leads the investigator to think they have found the answer. This is irrespective of how many actual levels (6-whys, 8-why-s, etc) are used. If you’re headed down the wrong path, you just get deeper in the wrong direction!

    5-whys is often thought of as a simple, easy method of finding problems. Honestly, I find it one of the most difficult to use. Somehow, you have to magically know the right questions to ask, prevent yourself from inserting your own biases, and then decide how many 5-why paths you want to take (one root cause? 3 root causes?). It takes a serious expert to properly use the system, and even the experts don’t seem to come up with decent answers (just look at the first post).

    I’ve given the same problem to 4 different teams simultaneously, and asked them to do a 5-why evaluation. All 4 teams got different answers. How can we think we are getting the right answers , when everyone gets different answers?

  • Maq says:

    I’d say

    1. �Why did the robot stop?�

    The fuse blew.

    2. “Why did the fuse blow?”

    The circuit overloaded.

    3. “Why did the circuit overload?”

    The bearings locked up.

    4. “Why did the bearings lock up?”

    Insufficient lubrication

    5. “Why was there insufficient lubrication”?

    insuffiecient circulation of oil (WE NOT STOPPING HERE, WE ARE NOT LIMITED TO 5 Y’S)

    6. “Why was there insuffient circulation?”

    Pump intake was clogged with metal shavings

    7. “Why were there metal shavings?”


    • Mark Paradies says:

      This goes beyond what the expert did but still isn’t good root cause analysis.


      1. If focuses on just one causal chain.

      2. It doesn’t lead you beyond your current knowledge.

      Every time I explain more faults with a 5-Why example, someone always says, “Yes … But I could ask more whys.”

      Of course, you could. But the expert didn’t.

      The end point is very dependent on what “Whys” were asked by a particular investigator rather than what the complete set of causes are.

      The 5-Why process doesn’t lead people to improved results.

      Almost every 5-Why I’ve reviewed either:

      1. Stops short on the chain of causation. (Especially in the area of human performance.)

      2. Misses major chains in a multiple chain caused incident.

      3. Jumps to conclusions not in the evidence (drives the process to meet their pre-determined end point).

      4. Ends without a complete understanding of what happened (and, therefore, can’t find all the causes because all the causal factors were not identified).

      This is hard to understand for those who have only been trained in 5-Whys and haven’t learned and used a system like TapRooT�.

  • krazzerz says:

    Consider these:

    – Use Why-Why Analysis in conjunction with other analysis tools like Ishikawa Diagram
    – You are not limited to just 5 Why levels, you can go deeper as you see it fit
    – Whether you use the structure/written Why-Why Analysis or not, people ask it (Why) in their minds anyways (“Why it happen…. How it happen…)
    – To make Why-Why effective, follow it up with How (5W1H or 5W2H)
    – All identified root causes have to be proven/confirmed against the reported problem
    – Accept the results with possible constraints. If you do a multi-level Why-Why and let say the result of the last Why is the “machine design”, you may have to stop there since you cannot change the design anyway. Accept the constraint that machine design cannot be changed. You can implement corrective/preventive actions within that constraint.

    I do not know TapRoot but if you really want to understand any Problem Analysis, it always follows the same principle. It follows the 8D for full blown problem analysis. The 7-Step TapRoot Analysis shows that. And within that 7-Step process, you still have to use analysis tools. See TapRoot Step 3-5. It’s a neat software tool but behind it, are old, crude tools people used to resolve their problem, just like the Why-Why Analysis.

  • Mark Paradies says:


    I’ve studied root cause analysis for a long time and I disagree.

    See https://www.taproot.com/comaping-5-whys-with-advanced-root-cause-analysis/

    By the way, I think TapRooT• pre-dates 8D.

    Best Regards,


  • chuck says:

    you really can’t depend on anyone to really give you a correct answer

  • Mark Paradies says:

    This is an amazing chain of comments.

    If you made it to here reading, you really have thought about the reasons some people like 5-Whys and the reasons why 5-Whys fails to produce adequate results in most cases.

    Good luck in picking an advanced root cause analysis tool!

  • Jeff Beeson says:

    There is one clear problem with 5-Whys, it is only as good as the experts working through the questions. You rarely discover anything new using 5-Whys and often the Root Cause is masked once a performance issue is discovered.

  • Luciano J. R. Ferreira says:

    My personal experience of using 5 Why tool is that the main deficiency it’s not related with the quality of the generated answers or the moment of stop the questions. It is the search of a “magic” root cause (ilustrated in the classical literature examples) instead of the set of root causes that acting together caused the problem (something that normally occurs).

  • Harjot Singh says:

    Hello Mark,

    Is it mandatory that we need to construct 5 Why�s when we are determine the cause.
    Or the root cause can also be find within 2-3 or 4 Why�s


  • Mukul says:


    I am working with a leading Automobile manufacturers in India.

    We have been using 5 Why method for a long time. My personal experience with this method is, if at all we reach the root cause in 5 Whys, and do not reach human error, I think we are not doing justice (Not to blame Humans). Almost 99% of the cases, any problem / issue boils down to a Human error.

    This is my personal opinion though.

  • Mark Paradies says:

    Yes, that is a common problem for 5-Why users. That’s one reason they find TapRooT� Root Cause Analysis superior.

  • Alvin Austria says:

    As I’ve back read all the threads of communication coming from you guys from 2007 up to this year 2016. Yes, right we cannot depend on only one tool to find the root cause of the problem. Maybe some of you are just depending on something that you are always using and not trying to go beyond other tools that will lead you to the right way and correct analysis in finding root cause.
    As my opinion in this thread Mr. Mark Paradies have the most expertise to explained how to deal with the right tool in finding the real cause of the problem. On the otherhand, 5 Why’s helps a lot in the industry to incrementally improves those organizations especially TOYOTA that are still using it today and continuously.

    Thank you.

  • I see that in this situation the 5 Why’s should have started with the Answer from combined 4 & 5. What we find is that individuals do not think first before giving answers and add information that causes overload and does not paint the correct picture of the situation.

    If in this situation we had started out with the 1st question being answered by the combination of A4&5 the next questions would have probably pointed to the breakdown of the equipment due to deficiency of upkeep.

    I took this more of an exercise to state that the 5 whys is very useful to bring your staff up to a point where they can identify the problem immediately and the remainder of the drill down will bring about pinpointing the need, area, extent of the issue for resolve.

  • J.Haslemore says:

    An interesting topic. The fact that this thread is still in discussion 10 years later certainly highlights the differing opinions regarding the use and effectiveness of 5 whys.

    5 whys can be a useful tool to determine causal factors, in some cases for more basic issues/problems, a root cause can be identified. One major issue with this tool is that it restricts the users line of thought to one set of causal factors. From each causal factor, may extend two or more other causal factors as opposed to having one for each, as seen in the example used for this thread. When used like this, it omits other issues associated with the original problem.

    The name also misleads users to believing that all you ask is “why” and that it is only required to be asked 5 times. This is certainly not the case. Asking why in a more meaningful/structured question allows you to consider or think of other alternative causal factors. For Example, if the car battery is flat, you might find that the alternate belt was slipping. Instead of continuing with just “why”, you might ask “why is the alternator belt slipping? What could potentially causing it to slip?” Instead of discovering only that the alternator pulley is loose, asking “what else cause be causing this” may reveal the belt was worn. Another contributing factor….

    Although it has its weaknesses, this can be a useful tool in determining causal factors. Being aware of the weaknesses, like any other causal analysis tool, will allow for a more effective outcome. In any case, it is always wise to use more than one method to identify causal factors to determine root cause.

    • Mark Paradies says:

      Thanks for the comment.

      I would guess that most people think they are finding root causes, not Causal Factors, when they use 5-Whys. I would also guess that most people who use 5-Whys do not use other technique to go beyond 5-Whys to find root causes. At least that has been what I’ve observed.

      To me it is amazing that after 10 years of seeing repeat problems (often the case when using 5-Whys), people still think that it works!

  • Luke Quinlivan says:

    The 5 Why’s model would be classified as a simple linear or “domino” causation model. This takes an assumption that if you were to remove any of the lead up factors in any one of the dominoes falling, you will have prevented the event from occurring. However, there may be numerous contributing factors to why any one of the contributing factors occurred. This would stop you from looking beyond one contributing factor to each failure in the chain of events. This is why most studies (e.g. Hollnagel, 2010) talk about complex non-linear models of causation for events/incidents. I.e. – that accidents can be
    thought of as resulting from combinations of mutually interacting variables which occur in real world environments and it is only through understanding the combination and interaction of these multiple factors that accidents can truly be understood and prevented – Hollnagel, 2010

  • Jayesh Trivedi says:

    With 5 why we can go ahead with one reason only and also not sure that we can reach up to root cause as in this case why so much metal came in filter?

  • Mark Paradies says:

    Five more examples of 5-Whys: https://www.taproot.com/best-5-why-examples/

  • Keith Terry says:

    For incidents that my company deems as “significant” we use TapRoot analysis to determine the root cause(s) and then apply 5 why to those to drive down a little deeper. This takes a root cause down to its fundamentals. So a root cause we see a lot is “Process not followed”. Well, if we start applying the whys to that we quickly start to drive down into driving a deeper understanding of human performance factors. Why wasn’t the process followed? “The boss said I could do it this way instead”. Why did the boss say that? ….. You get the picture. Some of this may drive down into personal accountability for decisionmaking but at the end of the day, by finding the answers to these questions you get much closer to the true root cause. There is quite a challenge in getting honest answers to some of the why questions but to know the real root cause of some incidents, that is the only way….

    • Mark Paradies says:

      Those whys should be covered under management Systems – SPAC Not Followed and then the Generic Cause for the root cause you identify. Also, if the person didn’t follow a well understood, well-enforced rule, the cause stops at SPAC Not Used. That is a potential cause for discipline.

  • Alan says:

    The question barely warrants an answer… In this business, if you really think “5-Whys” is effective, you should probably continue to use it and but maybe double-check with a Ouija Board…

  • Jim Krupp says:

    It never ceases to amaze me how so many Americans believe they are smarter than the father of the Toyota Production System, which inspired Lean Manufacturing in the U.S. The example is intended to be used as a teaching tool to instruct others how the technique can be applied, not the be-all-end-all solution to manufacturing problems. And “5 Whys” is a generic term for a technique, not an absolute limit; the actual number of questions can vary until the root cause is finally revealed (something that REAL practitioners understand). But in our arrogance, we choose to nitpick the example rather than focus on the methodology. After all, we have overlooked the one question that must still be asked after we have asked “Why?” the necessary number of times to arrive at the root cause: “HOW do we fix the problem?”

  • Mark Paradies says:

    Wow! 16 years since the first comment.

Leave a Reply

Your email address will not be published. Required fields are marked *