When I asked this problem around to co-workers (who have all at least a master in a scientific subject), very few could actually answer it properly. Most of the time, I suspect it is because they did not dedicate enough time to do it properly, and wanted to answer it too quickly.
It was more shocking that someone just out of school, with a major in probabilities could not answer that properly. It raises the question: what is all this education worth?
The results were not better as soon as the question was not exactly like what students in those masters are used to, like for example, this simple stochastic calculus question:
My opinion is that, today in our society, people study for too long. The ideal system for me would be one where people learn a lot in math/physics the first 2 years of university, and then have more freedom in their education, much like a doctorate.
We still offered the job to this person, because live problem solving is not the most important criteria. Other qualities like seriousness and motivation are much more valuable.
