>The purpose of an interview is to see if the person is a good fit for the position at hand
This depends on the position. If the position requires an MS degree and 5 years of experience you'd need to spend couple of weeks testing for the whole corpus of knowledge, that these requirements demand. It's quite expensive and few candidates are willing to spend this much time. The only practical way is to go with the credentials the person already has.
If you are looking for somebody to write websites using frameworks then, indeed, you can test all required skills in a day of technical interviews.
The handling of problems would be nice to know but, unfortunately, is hard to test. Somebody who just flew into the interview and is confronted by a bunch of strangers is not in the best shape to handle problems. If he can even in these conditions - good, now you know that this person can work under stress. Successfully solving simple puzzles though does not show anything more than this - you are likely looking for somebody to solve much harder problems that require weeks and months of research. Neither does a negative result mean much - this is most likely a result of stress.
So the brain teasers and "how many sorting algos you can write on a white board in 30 mins" type of questions, in my opinion, are useless. Asking concrete questions in the domain of the candidates knowledge on the other hand, lets you quickly verify much wider set of skills.
This depends on the position. If the position requires an MS degree and 5 years of experience you'd need to spend couple of weeks testing for the whole corpus of knowledge, that these requirements demand. It's quite expensive and few candidates are willing to spend this much time. The only practical way is to go with the credentials the person already has.
If you are looking for somebody to write websites using frameworks then, indeed, you can test all required skills in a day of technical interviews.
The handling of problems would be nice to know but, unfortunately, is hard to test. Somebody who just flew into the interview and is confronted by a bunch of strangers is not in the best shape to handle problems. If he can even in these conditions - good, now you know that this person can work under stress. Successfully solving simple puzzles though does not show anything more than this - you are likely looking for somebody to solve much harder problems that require weeks and months of research. Neither does a negative result mean much - this is most likely a result of stress.
So the brain teasers and "how many sorting algos you can write on a white board in 30 mins" type of questions, in my opinion, are useless. Asking concrete questions in the domain of the candidates knowledge on the other hand, lets you quickly verify much wider set of skills.