The 5 whys technique was originally developed by Sakichi Toyoda and was later used within Toyota Motor Corporation.

The “5” here is not the magic number or count limit. Instead, it is illustrated by deliberately and repeatedly asking the question "Why?” during an attempt to search for the basic cause of the problem.  The motive is to find the real cause of the problem and not just to eliminate the surface symptoms.

Taken from Taiichi Ohno, Toyota example:
1. Question: Why is the machine standing idle?
1. Answer: The fuse has blown due to overloading.
2. Question: What caused the overloading to occur?
2. Answer: The bearings were not properly oiled.
3. Question: Why were the bearings not properly oiled?
3. Answer: The oil pump was not working properly.
4. Question: Why wasn't the oil pump working properly?
4. Answer: The pump axle was badly worn.
5. Question: Why was the axle badly worn?
5. Answer: Dirt got into the bearings.

Now, the real cause of the problem can be eliminated, instead of merely treating one of the symptoms.

Application scope:
Simple application. Only applicable for simple problems.

Pitfall:
1) Asking "Why?" may be a favorite technique of three year old kid in driving you crazy. Then think about the reaction, if you keep perform this “Why?” to a worker (even worst without proper tone).

2) The objective can be targeted to finding thing, event or human. However, the end motive is “make" or "break” of this method usefulness.

Here, take the example to further elaborate:
(Inspector) Question: Why was the axle badly worn?
(Repairer) Answer: Dirt got into the bearings. The maintenance seems not properly done. (with unintentional negative bias suggestion)
Inspector: I will report the maintenance guy to office. (Even may not be truly maintenance fault)
This negative motive is not only causing maintenance people get fault, and maintenance dept also have to put extra resource to revise proper maintenance procedure. Instead of positive motive is to design better dirt protection.

To avoid pitfall, the positive motive (mindset) and mutual trust is really needed!

Your comment...