Keep asking why until the answers stop being restatements, then verify the last one against evidence rather than opinion. Five whys works as a discipline and a fishbone helps when several factors contribute. The test is whether removing the cause would genuinely prevent recurrence. Watch for causes aimed at a person, since those almost always hide a process or systems failure underneath.
Why interviewers ask this
Solving symptoms is the most expensive mistake in this role, so interviewers want proof that you dig. They listen for a repeatable technique, for verification against data rather than stopping at the first plausible story, and for the recurrence test. Recognizing that a human error root cause is usually a process design failure is the answer that marks out an experienced analyst from a keen one.
How to structure your answer
- Ask why until the answers stop restating the symptom.
- Verify the final answer against data, not opinion.
- Reject any root cause that lands on an individual.
- Apply the recurrence test before you stop.
Example answer
I keep asking why until the answers stop being restatements, and then I go and check the last one against data, because five whys with no evidence is just a chain of opinions that sounds convincing. The thing I look out for is when the chain lands on a person. If the root cause is that someone forgot to tick a box, that is not a root cause, that is where the analysis stopped, and the real question is why the process depends on someone remembering. On a billing issue the first answer was data entry error. Two levels down, the actual cause was that two systems used different customer identifiers and the reconciliation was manual, so errors were inevitable and the individual was just the last place they became visible. My final test is always whether removing the cause would have prevented it recurring. If it would not, I have not finished.
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See how it worksFollow-up questions to expect
- What do you do when the root cause is outside the scope of your project?
- How do you present a root cause that implicates a senior stakeholder's decision?
- How do you tell a root cause from a contributing factor?
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