It happens all the time, and it comes from a mix of things. One way it happens is that you get a PhD in astrophysics with years of data analysis experience in

It happens all the time, and it comes from a mix of things. One way it happens is that you get a PhD in astrophysics with years of data analysis experience in for a data science job. Have a software engineer interview her and he might find that she doesn't know a number of basic computer sciences concepts [traversing a linked list, tail recursion, implement breadth-first-search]. His knowledge background says these basic ideas are fundamental, there are therefore serious questions about the technical ability of the interviewee.