causes of the problem beyond the most apparent. The following principles are
a crucial part of the Toyota approach:
- The analysis must not be clouded by preconceived ideas of the problem
causes. If the cause is assumed, it will preclude a useful analysis and most
likely lead to poor results. - Always follow the genchi genbutsuprinciple to verify the source of the prob-
lem. Do not depend on others, or on data, to find the cause. Use informa-
tion to point toward the location to “go see.” The point of cause must be
observed firsthand. - Analysis is continued until it is certain that the true causes, or root causes,
of the problem are discovered (using the “Five-Why” method). - In nearly all situations there are multiple causes for problems, and thus
the analysis must be comprehensive. Toyota evaluates causes through the
4Ms: Man, Method, Material, and Machine. - Since there are many possible causes, it’s necessary to narrow to the most
significant ones. Narrowing allows the focusing of efforts to generate
greater results. - During the analysis, the goal is to identify problem causes that can be cor-
rected by the problem solver. This avoids the tendency to defer the problem
to others and forces the question, “What can we do?” - A thorough and complete analysis will yield root causes that will clearly
indicate specific, corrective actions. There is an observable and obvious
trail leading from the problem to the causes and to the solutions. - Thorough and complete analysis provides factual data, allowing precise
prediction of potential results when the causes are corrected. Determining
the exact result is an important part of the process since it forces the evalu-
ation of capability and effectiveness in examining a problem.
As with many aspects of the Toyota Way, the thought process is critical to
success. Notice that during the following conversation, people will jump to pre-
conceived conclusions rather than recognizing the simple but true answer to the
question. Using the example in the problem statement below, we would begin
the Five-Why process as follows:
Problem statement: “The fabrication units per hour is below goal.”
Upon asking our group “Why?” we might get the following answers:- Because the machines break down.
- Because operators are absent.
- Because we run out of parts.
- Because operators are not trained.
- Because the setup times are long.
Each of these answers may be “true,” as in the conversation between the
engineer and the lean sensei described in chapter 14, but they are further down