◆ Continually narrow to the most significant causes, and refocus the analysis
accordingly.
◆ Determination of root causes should provide a clear and obvious under-
standing of the necessary solutions.
◆ Analysis should be fact and data based. The root causes should be quantifi-
able, and the effect of improvement should be predictable in advance of
implementation.
354 THETOYOTAWAYFIELDBOOK
Reflection Activities
Following the problem you identified in the “Reflect and Learn
from the Process” section of the last chapter (remember, we told
you to keep it in mind?) complete the following activities:
- Make a list of possible causes for the problem, then narrow it
to the three “most likely” causes.
- Select one of these three causes and investigate further to
determine if this is an actual cause that will lead to the “root
cause(s).” Determination of root causes is the most important
element in the problem-solving process. Make sure your
analysis is thorough and complete prior to proceeding to the
corrective actions.
a. Go to the area where the problem occurs to see it firsthand.
b. Observe the situation and use the Five-Why method to fol-
low the likely cause through to the root cause. The answer
to each “Why?” should be based on factual information that
is seen firsthand. Do not do this based on “speculation.”
c. Use the “Therefore” method to track back to the problem
statement to verify the accuracy of your logic.
d. Is it possible to provea connection between the problem,
the most likely cause, and the root cause(s)? (If you can
make the problem occur, or stop at will, you’ve proven a
root cause.)
- Locate the “point of cause” (the actual location where the root
cause occurs and the problem originates).
a. Many large problems have several root causes and thus
several points of cause. Identify the three most significant
ones.
b. Keep evaluating until you find the actual point(s) of cause
(you can see the problem occur).
