(Photo: Ad Meskens)
If you’ve ever had training on root cause analysis (RCA) you will almost certainly have learnt about Five Whys. Keep asking ‘why’ five times until you get to the root cause. The most famous example is of the Lincoln Memorial in Washington. The summary of this Five Whys example is reproduced below from an article by Joel A Gross:
Problem: The Lincoln Memorial in Washington D.C. is deteriorating.
Why #1 – Why is the monument deteriorating? Because harsh chemicals are frequently used to clean the monument.
Why #2 – Why are harsh chemicals needed? To clean off the large number of bird droppings on the monument.
Why #3 – Why are there a large number of bird droppings on the monument? Because the large population of spiders in and around the monument are a food source to the local birds
Why #4 – Why is there a large population of spiders in and around the monument? Because vast swarms of insects, on which the spiders feed, are drawn to the monument at dusk.
Why #5 – Why are swarms of insects drawn to the monument at dusk? Because the lighting of the monument in the evening attracts the local insects.
Solution: Change how the monument is illuminated in the evening to prevent attraction of swarming insects
This example is easy to understand and seems to demonstrate the benefit of the approach of Five Whys. Five Whys is simple but suffers from at least two significant flaws – i) it is not repeatable and ii) it does not use all available information.
Different people will answer the why questions differently and their responses will take them to a different conclusion. For example to Why #2 “Why are harsh chemicals needed?”, the response might be “Because the bird droppings are difficult to remove with just soap and water”. This leads to Why #3 of “Why are bird droppings difficult to remove with just soap and water?” and you can see that the conclusion (“root cause”) will end up being very different. The approach is very dependent on the individuals involved and is not repeatable.
Other questions that would be really beneficial to ask but would not be asked using a Five Why approach are:
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- When did the problem start? Armed with the answer to this might have helped link the timing with when the lighting timing was changed.
- How many other monuments have this problem? If other monuments do not have this problem then what is different? If other monuments have this problem then what is the same? This line of questioning is, again, more likely to get to the lighting timing quickly and reliably because a monument without lighting and without the problem suggests the lighting might have something to do with the cause.
In my last post I described a hypothetical situation of a vaccine trial where subjects had received expired vaccine. If we use the Five Whys approach, it might go something like:
Why did subjects receive expired vaccine? Because an expired batch was administered at several sites; Why was an expired batch administered at several sites? Because the pharmacists didn’t check the expiry date; Why didn’t the pharmacists check the expiry date? Here we get stuck because we don’t know. So maybe we could try again.
Why did subjects receive expired vaccine? Because an expired batch was administered at several sites; Why was an expired batch administered at several sites? Because the expired batch wasn’t quarantined. Why wasn’t the expired batch quarantined? Because sites didn’t carry out their regular check for expired vaccine. Why didn’t sites carry out their regular check for expired vaccine? Because they forget maybe? Or perhaps didn’t have a system in place? As I hope you can see, we really end up in guess work using Five Whys because we are not using all the available information. Information such as which sites had the problem and which didn’t? When did the problems occur? What is the process that ensures expired vaccine is not administered? How did that process fail?
Five Whys can be fitted to the problem once the cause is known but it is not a reliable method on its own to get to root cause. Why is definitely an important question in RCA. But it’s not the only question. To quote the author of ‘The Art of Problem Solving’, Edward Hodnett, “If you don’t ask the right questions, you don’t get the right answers. A question asked in the right way often points to its own answer. Asking questions is the ABC of diagnosis. Only the inquiring mind solves problems.”
Here are more of my blog posts on root cause analysis where I describe a better approach than Five Whys. Got questions or comments? Interested in training options? Contact me.
Note: it is worth reading Gross’s article as it reveals the truth behind this well-known scenario of Lincoln’s Memorial.
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