Root cause analysis techniques begin with a clear problem statement, after which we go on to identify possible causes. These are then investigated further by gathering concrete evidence to either confirm or refute their prevalence, with prevalent causes carried forward into the analysis, until ultimately, we are able to identify the root cause of the problem.
Several possible causes may be prevalent at any one point in time. The process of identifying possible causes should however result in a number of possible causes that are independent of each other. What this means is that while there may be more than one prevalent cause responsible for the problem, each possible cause identified should feasibly be able to result in the problem occurring on its own should it be prevalent. Compartmentalising possible causes in this way brings clarity to the problem solving process and also supports important processes such as evidence gathering.
A simple way to do this is to begin with the identification process, identify one possible cause, and then with each additional possible cause identified, to assume that the possible causes identified up until that point are not prevalent. The simple introduction of the word “but” after expressing each possible cause in the negative leads into the identification of each successive possible cause.
So, say we are served a cold cup of tea and want to establish why. There are several possible causes. We begin with a shortened form of the problem statement:
“We were served cold tea” and then begin the process of determining why we were served cold tea.
Possible causes are as follows:
- The tea was allowed to cool down after it was prepared
- Too much cold milk was added to the tea during its preparation
- The water used to prepare the tea was not hot enough
Before identifying possible causes 2 and 3, we would express possible cause 1 in the negative followed by the word “but”, and then go on to identify possible cause 2. So, we would say: “The tea was NOT allowed to cool down before it was prepared, BUT too much cold milk was added to the tea during its preparation”.
In identifying the next possible cause we would say: “The tea was NOT allowed to cool down, an excessive amount of cold milk was NOT added to the tea, BUT the water used to prepare the tea was not hot enough” and so on.
By taking this approach we not only ensure the independence of each possible cause, we also facilitate the development of additional possible causes, since we clarify our thinking by eliminating the possible causes we have already identified.
Not all possible causes are independent of each other, and there are times when more than a single possible cause is required to be prevalent in order for a problem to occur. What this technique does is help us to identify a wider range of possible causes.
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