Purpose of Article

The Three-Legged Five Whys procedure is said to be used in some parts of a major auto manufacturer as well as other companies - perhaps the auto company’s suppliers. Judging from what was added to the Five Why procedure, we think that the authors sought to remedy what they saw as missed opportunities of problem detection and system improvement.

Our conclusion is that the three legs procedure we reviewed, taken as a whole, is not a step forward and will create confusion and additional misapplications. For us, misgivings first arose when we read the introduction slide for the course teaching the new method:

3 legged 5 Why Analysis /
Extremely easy to Explain / Extremely difficult to do Correctly

We would rather have a procedure that is simple to explain and easy to use.

Later in the article we evaluate two examples for logical consistency that are used to teach the approach, and find them lacking.

The Basic Five Whys

Definition

The basic “Five Whys” analysis is a procedure suggested by Masaaki Imai for troubleshooting problems. It was made popular as part of the Toyota Production System (1970’s.) Application of the procedure involves taking any problem and asking “Why - what caused this problem?” Then, when the cause is identified, asking “Why?” again (i.e. “what caused the cause?”) The strategy, as commonly understood, is to ask “Why” five times or more uncovering links in a causal chain going back in time.

Purpose

The purpose and the power of asking “Why” successively is that, when done correctly, it leads away from lower level symptoms (e.g. defective parts or errors of omission) up to higher level causes (e.g. policies, procedures or management decisions.) Resolving these higher level sources of problems allows an organization to evolve its technical and human systems. System evolution is a strategic advantage helping to assure a successful future. But, to get to the system level may sometimes require several more than five whys. For tips on how to do the basic Five Why approach see the article entitled “Five Whys - How To Do It Better” on our website.

Three Legged - Five Why Analysis

Source of our information about the procedure

One of our sources reports that a former employee learned it while at a major automobile company and is promoting its use in business and industry. (However, our source also reports that a current employee of that company does not recognize the modified procedure as something used at present in their organization.) The slides seem to allude to supplier issues which may explain why the employee had not heard of it. It may be something being taught to their suppliers rather than in the organization itself.

Description of the three legs

The new procedure creates three lines of inquiry. The “Why, Why, Why … ” process is applied independently to each of the following lines (legs):

I. Specific Leg

Why did this specific situation happen? This is the normal non-conformance being analyzed using the Five Why Procedure.

II. Detection Leg

Why was this situation overlooked? This asks why didn’t our in-place detection procedures catch this.

III. Systemic Leg

Why did the possibility exist for this situation to occur? This asks you to look at what about the larger organization, systems, or procedures creates an environment in which this non-conformance occurred?

BPI’s opinion of the Three-Legged Five Why process

After reviewing descriptive material showing examples of the Three-Legged Five Why approach, we have the following opinions:

Separate Detection Leg

  • The use of a separate Detection Leg should only be triggered when a detection point is already part of the process and has failed. When a detection point is NOT part of the existing system, the issue of whether or not to insert one should be addressed using a Decision Making process but only after the root cause of the problem is known. (The intention of the procedure’s authors was not clear.)
  • A Root Cause diagram can be used to show the step-by-step creation of a problem and any detection failures - much like a process diagram shows the steps of a process. Detection failures can be shown as failed “gates” i.e. a separate problem with their own series of steps leading up to the point of detection failure. We have used this diagram method for almost 20 years with much success and no confusion. So, as it turns out, we have been using a “two-legged Five Why” procedure, but only when an existing detection point has failed.

Separate Systemic Leg

  • A separate Systemic Leg is not necessary and logically is not separate from the causal chain uncovered by the Five Why procedure. As each Why is investigated the analysis will lead to any policy, procedure or management decision that triggered the causal sequence. The key is to be able to use the basic Five Why procedure properly.
  • Having a separate Systemic Leg separates the analysis from the facts of the causal chain and this will inevitably lead to moving into generalities and conjecture.
  • Not all problems will be due to higher level causes. But, when it is documented that many lower level problems are traced backward in time to the same higher level source this will point to a policy or procedure or management decision that should be reviewed in order to correct the downstream effects.

Summary of Opinion

We can support a two-legged Five Why when an existing detection point has failed to catch a problem it was supposed to catch. We do not recommend addition of the third systemic leg because use of the basic Five Why procedure, by itself, will lead from specifics of one problem back in time to higher level, system causes. A third leg will likely lead to conjecture rather than documenting how a particular problem came into being.

The BPI Problem Solving process can be used to answer “Why?” when the answer is unknown and requires some analysis to determine. The BPI Decision Making process is used to develop or select the best corrective action after the necessary root cause information is known.

Critique of 2 Three Legged teaching examples

What follows are examples from the Three-Legged Five Why slide presentation we reviewed. We were told that these slides are used to teach others about this more “advanced” technique. Example A, is a non-conformance leg of a problem and example B is a detection leg for another problem. Both examples state the triggering link (i.e. oldest link) in the causal chain is a failure to implement a preferred solution. In other words, decision making and cause analysis are confounded in these examples (and they should NOT be.)

Critique of examples that confuse decision making and cause analysis

Example A, Non-Conformance Leg:

  1. PROBLEM: Missing O-ring on part number XXXX
  2. WHY? Parts missed the O-ring installation process
  3. WHY? Parts had to be reworked
  4. WHY? Operator did not return parts … after rework
  5. WHY? No standard rework procedures exist.

Comments: It is not clear to us what teaching point this example was meant to make. But we will use it to make several points of our own.

First, we disagree that #2 was caused by #3. We believe it was caused by #4. Note that “parts (needing) to be reworked” would happen first and then “operator not returning the parts to the process after rework” would follow. The causal chain has a flawed chronological sequence, a logical error.

Second, the slide circles #3, “Parts had to be reworked”, and indicates this should be pursued to uncover why rework was necessary. We agree, but the particular non-conformance should not be part of this series of Whys because it answers no Why. The series should read: #1 caused by #2 which was caused by #4. (Missing O-ring on part number xxx because parts missed the O-ring installation process because the operator did not return the parts after they had been reworked.)

Third, #5 asks why did the “operator not return parts … after rework?” and answers “no standard rework procedures exist.” But this answer assumes a solution.

The argument amounts to this - the reason the operator did not return parts after rework is because “we have not implemented my idea of having a standard rework procedure.” But, we might argue with equal confidence that the reason the operator did not return the parts is that “we did not implement my idea of having a worker orientation program to teach new workers about how our process works,” or someone else’s idea to “only hire rework people with a track record of making decisions that consider downstream effects.” So, this is not a cause analysis but a logical error.

(We are unable to say why the operator did not return parts after rework in this case. Perhaps the unit was overwhelmed with rework, or the parts were delivered to the wrong location, or the worker that knows how to do things was absent. We do know that the cause was not a missing standardized procedure, although the cause might well be ignorance of what to do. We agree that a standardized procedure would be one solution to consider.)

Example B, Detection Leg:

  1. Problem: Missing threads on fastener part number YYYY
  2. Why? Did not detect threads were missing.
  3. Why? Sensor to detect thread presence was not working.
  4. Why? Sensor was damaged.
  5. Why? We have no system to assure sensors are working properly.

The series above gets off to a misleading start by indicating that the cause of the missing threads (#1) is failure to detect threads were missing (#2). Of course this is false. There are actually two problems here. One problem is that we made parts with missing threads. This has its own chain of causes. And, problem two is that after we made parts with missing threads our detection step failed to detect this problem. This also has its own separate chain of causes. So, this leg should start at #2.

Note #5 asks why the sensor was damaged and answers because we have “no system to assure sensors are working properly.” This is the same logical error as described in the example (A) above. The cause of something is never the failure to implement a future solution. The sensor was ineffective for some reason. Find that reason. After you know what you need to know, then go on to Decision Making and decide what to do about it. Maybe you will select a system to test sensors or maybe you will add a back-up sensor or whatever.

Selecting an action to correct a problem is not the same as identifying the cause.

Don’t confuse the selection of a corrective action with cause analysis. This is a creativity killer. When a decision is made under the guise of cause analysis, viable options are not even brought to conscious awareness! For, after all, if the cause is a lack of some procedure, the solution is “supply that procedure.”

Summary

HYPOTHESIS: Critical thinking can boost creativity by avoiding self-serving causes/solutions disguised as objective analysis. Organizations interested in helping people think more clearly as one means to support innovation are invited to contact us!