We are sometimes asked how the Kelvin TOP-SET Root Cause Analysis (RCA) system compares with other RCA systems.
So, what about '5-Whys'? To make the comparison we first ask, "What does the phrase '5-Whys' imply?" It implies that you have to take five 'Why' steps to get to a Root Cause. We don't agree. And it implies that the steps are linear with no divergence or convergence. We don't agree.
Let's compare the two systems using an imagined but tragic incident, which happens all too often:
A 3-year-old girl falls into a garden pond and drowns. Can we undertake a 5-Why analysis on this? Yes.
1. Why did she drown?
Because she fell in the pond
2. Why did she fall in the pond?
Because she slipped
3. Why did she slip?
Because the ground was muddy
4. Why was the ground muddy?
Because the garden was being renovated
5. Why was the garden being renovated
Because her parents wanted to improve it
These five whys lead to a Root Cause, but the Root Cause, although true, isn't very helpful.
Take a look at the our analysis of the same incident below, and you get a totally different picture. The Root Cause is much more useful and informative, and many more related issues are addressed. The beauty of the Kelvin TOP-SET system is that there is no insistence on using five whys, and there is the freedom to diverge (branch out) or converge (come together) where necessary. Click Image below for larger view.
In truth, six criteria must have been met before this girl could drown: (1) She had to slip, (2) there must have been no barrier, (3) the water had to be deep enough for her to be submerged, (4) she must have been unable to swim, (5) she must not have been wearing a floatation device, and (6) she must have been unsupervised. She drowned because all six criteria were met. If you fixed any one of these, she would be alive and well.
The analysis shows that the Incident Statement is crisp and clear, and each part can be questioned easily.
Moreover, there can be as many Immediate Causes as you like, and as many 'Why' steps as you need. In this particular example there are six Immediate Causes, which is more than normal, and a maximum of four 'Why' steps, which is more than adequate to complete the analysis.
To conclude, the major problem with the 5-Whys is that it can easily result in much important information being omitted from the analysis. This is not good. The Kelvin TOP-SET analysis system is certainly SIMPLE but it is not SIMPLISTIC. There is another serious flaw with the 5-Why approach, but that will be explored in the next article.