5. A little history
Toyota production system
"the basis of Toyota's scientific approach . . .
by repeating why five times, the nature of
the problem as well as its solution becomes
clear."
6. What is 5 whys?
Technique is to determine the root cause of
a defect or problem
Iterative question-asking technique used to
explore the cause-and-effect relationships
underlying a particular problem
Empirical observation
7. Example
The vehicle will not start. (the problem)
Why? - The battery is dead. (first why)
Why? - The alternator is not functioning. (second why)
Why? - The alternator belt has broken. (third why)
Why? - The alternator belt was well beyond its useful
service life and not replaced. (fourth why)
Why? - The vehicle was not maintained according to the
recommended service schedule. (fifth why, a root cause)
8. people do not fail, processes do
the real root cause should point toward a process that is
not working well or does not exist
classical answers :
not enough time
not enough investments
not enough manpower
May be true -> but are out of our control
Instead of asking the question why?, ask why did the
process fail?
9. To notice
Simple and robust
Drawbacks:
POV
Not data driven
Not for complicated problems
Focus on facts
10. Example 2
My customer is unhappy (the problem):
Why? – I didn’t deliver the project on time. (first why)
Why? – The job took much longer than I thought it would. (second
why)
Why? – I underestimated the complexity of the project. (third why)
Why? – I didn’t develop a proper plan and quickly made an
estimate of the time required. (fourth why)
Why? – I was running behind on other projects and lacked the time
to plan. (fifth why, a root cause)
