Sample Question #29 (statistics)
How do you calculate sample variance? Show me the formula and implement it in C or C++.
(Comment: I was asked this question at a hedge fund interview a few years ago – and I got both parts wrong! Needless to say I was feeling utterly mortified and defeated, and I didn’t get the trader job. The moral of this little story is: never assume a quantitative topic or interview question is "too" easy!)