The interview itself.
What I have observed is that interviewing is generally composed of one or more of a very small number of techniques:
Free-form, gut-feel unstructured or semi-structured chat and questions between candidate and hiring manager.
More formal pre-defined questions structured and consistently asked to all candidates.
Some variety of standardised test, essentially IQ based.
Questions posed by a technical expert with a desire to highlight his superiority rather than assess your capability.
A technical test or series of technical questions intended to be pragmatic and fair.
Aggressive panel questioning
Psychometric testing: verbal/numeric/diagrammatic reasoning or personality tests.
Presentation by interviewer on why the candidate should work for you.
There are studies and statistics that rank the effectiveness of the different techniques for selecting good candidates, I won’t pour them out here – I am not an expert and I’d just embarrass myself. But in my experience 1 is the most common, often combined with 4 or 5. But logic states that 4 is a waste of time and puts off candidates, and studies show that 1 and 5 are actually very, very poor indicators of ability and capability for the role and do not result in long-term success.
So what works?
2, 3 and 7 are by far a better method of assessing candidates, followed by an independent panel-decision based on the documented evidence taken from the interviews – the interviewer should not be allowed to make the decision independently as they display bias (subconscious or otherwise).
But 2, 3 and 7 are hard, it requires yet more work on what is already a tough and time-consuming process, so very rarely gets done.
The reciprocal nature of an interview (8) is so often overlooked, if you want the best people and you want to get the best out of them, then not only do you need to decide if they are right for you, you need to convince them that your business/team is right for them. You should be putting as much effort in to impressing candidates as they put into impressing you. You are competing for them in a buoyant market.
Doing it right.
As an interviewer, my best experience has been for a company that did a combination of 2, 3, 7 and 5. We put a lot of effort into interviewing, but the majority of people still failed the combination of tests, especially the technical test. The test felt ‘easy’ to us and some candidates did well, but the results didn’t match the apparent skills of candidates, in hindsight I think it confused the process. The problem is that technical tests are not effective at assessing ability during an interview, there are simply so many other factors at play.
Relying on structured questions, IQ tests and psychometric tests may feel clinical and impersonal, but very likely the best way to find the right candidate. But ego plays a role and when hiring for a team, we are only human and so many hiring managers want to rely on their own instinct, even if evidence demonstrates this is unreliable, so it is hardly a surprise that many hiring managers favour their instinct over a structured process.