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Comment by hectormalot | Hacker News Reader

“I’d like to understand how you structure problems, we can do a different topic if you like?”

“With ~50M people capable of clicking ads, and assuming they click one ad a day at 20cnt CPC, it would be around 3.6bn. I think my assumptions are on the high side, but order of magnitude is probably correct”

If done well, solving a problem (not a brain teaser) together can yield insight in how people approach new challenges.

If I’m hiring for someone to do what they already know this indeed not a useful question. on the other hand, if I expect the role to tackle various business problems as well I’m not sure what would be a much better way to get a sense on this. (Specifically because I’d want to discuss a not-too-complex problem that is outside your usual area of expertise)

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What I find weird about these questions, is that they are expected to be answered without any research? How often do you expect your people to solve a problem in a domain they know nothing about without doing any research? And the given example is odd, a lot of useful information that would help to answer the question will be public, and the obvious way to answer the question would be to look it up, before estimating the stuff that isn't public (but you won't know what information is publicly available until you look for it)

In the context that I've seen them used, the interviewer usually provides information if asked (and says so up front). e.g. if you don't know the # of inhabitants of Italy it should be completely okay to ask.

In any case I don't think it is about the calculation or the final number. It's really the approach that you develop that's interesting.

I've seen this mostly used in (management)consulting though, where you actually are regularly expected to solve problems that you might not have deep understanding of. When I was interviewing developers I discussed how they would architect an application to solve a specific problem. It gives similar insight and is closer to the actual job.

The problem is that the interviewer asks for a number. If the question was phrased as "How would you go about finding out the GoogleAds B2B revenue in Italy for 2017, which tools and methods would you use", I'd totally go for that question.

The reason is that to many people (myself included) your answer above is nonsensical.

  “With ~50M people capable of clicking ads, and assuming they click one ad a day at 20cnt CPC, it would be around 3.6bn. I think my assumptions are on the high side, but order of magnitude is probably correct”

Where did the "people capable of clicking ads" 50M estimate come from? Why one ad a day on average? Why not 0.2? Or 15? Why 20c CPC and not 0.001 euro cent? Why not 1USD?

I'm all for "first-principals based structured thinking" but asking someone to demonstrate that by generating a rudimentary formula, that won't survive any contact with reality, and populate it with almost completely random values, seems like a weird way to go about it.

It's typical of people who think that a tiny amount of knowledge makes them experts in anything related to reasoning and data, as a good number of practitioners in this field do.

It's about knowing how to structure problems, whether the components are public or whether the problem space is completely unfamiliar.

E.g. someone who guesses "$3 billion" on only a gut feeling likely wouldn't be a strong hire even if the number is correct, while someone who can correctly decompose the final answer into its components and make reasonable estimates would be a much better candidate.

For estimation interview questions, and problem-solving questions more generally, a "structural" approach to breaking down problems is important because on the job the interviewee will need to be able to identify what levers are available to them.

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