I found that Facebook was really bad for this. I'm a math undergrad, and I applied for a bunch of data analysis positions with them.

I was asked, as part of my application, to take a programming quiz. The quiz consisted of a graph theory problem. I did pretty poorly on it, given that I have no real knowledge of graph theory.

Had they asked me a question about statistics (or something similarly related to data analysis), I think I would have actually been able to answer, or at least been at a point where my programming knowledge- not my math knowledge- was what was holding me back.