Five Whys

I am a lean “coach” and I teach A3 in my company. Every lean book mentions the “five whys” and I can see their power in theory, but I struggle with them in practice. Any tips?

First of all, congratulate yourself on admitting that you find the “5 Whys” difficult. I have been walking the gemba two to three times a week for as long as I can remember, yet I can’t think of more than a dozen examples of truly insightful “5 whys” analyses. I clearly remember the latest case, a few months ago, at a company that makes industrial equipment. The production team was trying to understand a recurring quality problem and finally came to the conclusion that two key elements of the product were not interacting as expected. A member of the engineering department was part of the problem-solving group and he agreed to share the problems with his colleagues, which finally revealed that an opinion common to all the engineers was false: they had a mistaken mental model of how their product worked. Consequently, they ran experiments until they solved the problem on that specific product and are in the process of checking the others. As you can imagine, many planets have to align for this kind of problem to be solved. First, production persistently kept trying to solve a quality problem they had previously given up on; second, engineering got involved (such teamwork is never a given, neither in this company nor in any other I know); third, they rigorously tested factors until they narrowed them down to one they had previously thought might have no impact; finally, they kept asking “why?” until they concluded that their thinking about the physical interaction of components was wrong. This was a truly magical “lean moment”, but, on the other hand, it doesn’t happen often. Many “five whys” exercises I have witnessed remain superficial, go around in circles or end with a change to the process without first having understood the problem (thus investing in a solution, after which the problem comes back).

Let us apply lean thinking to the “five whys”: what is the appropriate evaluation method for a “five whys” analysis? Performance gaps (gaps) in the process are an indication that you are controlling the wrong set of parameters – if you know which parameters affect process performance, you solve the problem quickly; it is a matter of turning the knob back to the standard value. In many cases, however, limited process capability stems from the fact that we simply don’t know what the driving parameters are. A successful “five whys” analysis is what leads you to discover the appropriate control parameter. In Ohno’s classic example (taken from his book on the Toyota Production System):

1. Why did the machine stop? There was an overload and the fuse blew.
2. Why was there an overload? The bearing was not sufficiently lubricated.
3. Why was it not sufficiently lubricated? The lubrication pump was not pumping sufficiently.
4. Why was it not pumping sufficiently? The shaft of the lubrication pump was worn and rattling.
5. Why was the shaft worn? There was no strainer and metal scrap got into the pump.

We can see it moving from the machine’s load to the lubrication of the bearing, to the pump, to the wear of the shaft, to the protection of the shaft: in order to solve the problem, we no longer control the machine overload, but the entry of metal scrap into the pump. This classic example also shows why the “five whys” are so complex: in the same situation, anyone with less intimate knowledge of the workings of the machine could have answered differently and steered the “five whys” to a completely different conclusion. The measure of a successful “five whys” analysis is when it leads you to change your mind about which driving parameter to control to ensure process capability.

This, in turn, reflects exactly the kind of deep thinking that the “Thinking Production System” is supposed to develop. Most technical problems have multiple causes and impacts (anything simpler can be solved at a glance). Toyota’s problem-solving style is about learning to turn a multiple-cause, multiple-impact problem into a one-to-one cause-effect problem, identifying which cause (of all potential factors) is responsible for the big impact (of all potential impacts). Developing the knowledge to correctly substitute the right cause-effect model for a multiple-cause/impact situation is, in effect, wisdom – and it requires hours of practice at narrowing down technical problems. This kind of wisdom lets you start the “five whys” analysis in the right place. If not, who knows where it will end up. The key to a successful “five whys” is a correct understanding of the current state. Without narrowing down and specifically describing the current state, asking “why” several times will probably lead you... nowhere.

A lot of hard work needs to be done before embarking on the first “why?”:
potential factors causing the problem have to be identified and tested one by one:

As Art Smalley described in the article we wrote (The Thinking Production System), in his first problem solving at Ohno’s engine plant he had to test more than ten factors before arriving at the fact that the machine was producing defects because the lubrication fluid was contaminated by bacteria. When he proudly announced his findings to the supervisor (after hard work to reach them), the supervisor simply asked: “why is the fluid contaminated?”. Art had the right factor to understand the current state. Now he had to find the root cause.

In my experience, it takes a certain maturity for problem-solving groups to really stay the course and search for the cause properly. In most companies, the group just wanted to “fix” the problem and find the first way it could to make the problem go away. The “five whys” have a completely different goal: to develop technical expertise in the people conducting the analysis by finding the correct root cause. The companies I know that are getting there tend to talk less in terms of general processes and more in terms of technical expertise. They have realized:

1. How lean your process is reflects the technical skill of the people in the process: the most skilled people can run a business and, on the other hand, making a process lean without the necessary skill only leads to a well-designed process with poor performance.
2. “Lean” is not a thing in itself, but a method to develop high expertise and teamwork (in the words of Jeff Liker in “The Toyota Way to Lean Leadership”), which in turn leads to better judgment, leaner processes and sustainable results.

Many managers I know are uncomfortable with this. They like the straight line of fixing a process: they can ask (change this) and see a direct result (or not, more likely). The dotted line of training people and then seeing results improve, even though experience shows it is more effective, is harder for many managers: it requires a leap of faith in people’s autonomy and attitude that they seem reluctant to accept. Yet we all know the economic value of mutual trust.

To answer your question, it is difficult to give specific advice on how you conduct your “whys” so far from the gemba, other than to reflect on your expectations of what a “five whys” analysis is and does. To practice the “five whys” correctly, you must first master:

1. Having a clear mental picture of how the technical processes should work.
2. Being able to correctly identify the point of cause where the technical process misbehaves.
3. Listing the potential factors of variation and testing them one by one until you can confirm the main cause-and-effect relationship.
4. And then asking why.

The “five whys” cannot be practiced at a generic level – it is a practice for developing specific knowledge and makes no sense when separated from the real technical process to which it is being applied. The greater the expertise, the more relevant the “five whys”; the lesser the expertise, the more dubious the “five whys”. I am not saying you shouldn’t practice the “five whys” at every opportunity – it is a great way to get people thinking beyond the immediate work around them – but that you should accept that the outcome of the exercise is closely tied to the depth of technical understanding of the people in charge. In effect, the first step in conducting a “five whys” analysis is to assess the level of expertise of the people in the group and, if necessary, invite more expert people to guide the discussion.

Like any lean tool, the “five whys” are a practice and cannot be taught other than by practicing repeatedly. It takes roughly 10,000 hours to master any skill, so don’t get discouraged and keep practicing at every opportunity, but try to keep the ideal in mind – a better understanding of cause-and-effect relationships in technical processes – in order to get the full value of every “why” you ask.

Portuguese translation by Tamiris Masetto Manzano.