The reason that such a stark contrast can exist is because most technical questions test for knowledge rather than aptitude.
Tuesday, January 19, 2016
I have sat through too many interviews where the candidates claimed to have plenty of experience and they were even able to rattle off good answers to all of the technical questions, but then, when I would ask them to actually write a short program to solve a simple problem, they were totally unable to do so. Sometimes the contrast was downright shocking. Situations like this make two things readily apparent. First, requiring candidates to write actual source code as part of the interview process is crucial. Second, standard technical questions are not always effective.