At Toyota, a five-why analysis is often used as part of a seven-step process they call “practical problem solving.” Before the five-why analysis can begin, “practical problem solving” requires you to clarify the problem or, in Toyota terminology, “grasp the situation.” Trainers who teach this methodology within Toyota have found the most difficult part to learn is grasping the situation thoroughly before proceeding with five-why analysis. Grasping the situation starts with observing the situation with an open mind and comparing the actual situation to the standard. To clarify the problem, you must start by going to where the problem is (genchi genbutsu). This may include prioritizing a number of different problems in a Pareto analysis. The Pareto diagram uses bar graphs to sort problems according to severity, frequency, nature, or source and displays them in order of size to show which problems are the most important. It is probably the most often used statistical analysis tool within Toyota—simple, but powerful.
At this point you also want to set targets for improvement. Then you make a first attempt at identifying the point of cause (POC). Where is the problem observed? Where is the likely cause? This will lead you upstream toward the general vicinity of the root cause, which you can discover through five-why analysis. The ultimate purpose of the exercise is to generate and implement a countermeasure and evaluate the results. Only at this point, if the countermeasure is effective, does it become part of a new standardized approach.
The seventh step—standardizing the new process—is very important at Toyota. As mentioned in this chapter and discussed in Standardized Tasks Are the Foundation for Continuous Improvement and Employee Empowerment, standardization and learning go hand in hand and are the basis for continuous improvement. If you do not standardize the improved process, the learning up to that point falls into a black hole, lost, forgotten, and unavailable for further improvements.
Tools, techniques, and metrics aside, Toyota’s greatest emphasis is on thinking through problems and solutions. At Toyota, it is said that problem solving is 20% tools and 80% thinking. Unfortunately, I’ve learned from many Six Sigma programs that some companies get caught up in using all the great and new sophisticated analysis tools, where problem solving seems to be 80% tools and 20% thinking.