Video: How Many Interview Questions To Ask?

One question I get a lot is how many interview questions to ask when you're interviewing candidates. Five to six is about the right number, assuming your interview is about an hour long. 60 minutes is the median time that most interviews go right now. If you can do longer than that, great, that's super, but most people do about an hour-long interview.

Now, if you take that 60 minutes, and look realistically at how many interview questions to ask, figure ten minutes at the beginning is going to be rapport building, pre-ambly sort of stuff. And ten minutes at the end, that's usually going to be "So what questions do you have for me?" That leaves you about 40 minutes in the middle to really get to know this person, and that’s where we need to focus when deciding how many interview questions to ask.

Now, some people go in and they bang through interview questions, there is no limit to the number of interview questions to ask. They have 15, 20, of these things. The problem is when you do that, the candidate doesn't really give full, complete answers. Here's why that's problematic: most reasonably intelligent people can lie about most things for at least a minute. If you started to ask me about a topic of which I had no idea, say, for example, what's the implications of quantum physics on the gravitational forces of a black hole? I don't honestly even know if that's a real question. But assume it is, I could start and go "Well, you know, that's a really fascinating question, and there have been many times in the course of physics where we've had significant paradigm shifts, and while we knew about gravitational forces of black holes, the real question is what happens with quantum physics and the implication for that?" I can ramble on like this for a good 60 seconds, and if I use the words enough times it might actually start to sound like I have some clue as to what I'm talking about.

When you're doing a job interview, you want to make sure that you get this person to talk to you for at least two, two and a half to three  minutes, because you need to get them past the line where they can keep lying about something. And that’s going to influence the number of interview questions to ask. I could talk for a minute rambling about nothing, but make me talk for two minutes, well now it becomes pretty clear that I have no idea what the implications of quantum physics would be on the gravitational forces of a black hole. I have no idea whatsoever. But you need to keep me talking for at least two to two and a half minutes to figure that out.

So when thinking about the number of interview questions to ask, if you go into an interview with a good five or six really open-ended questions, you're going to force this person to talk to you for two, two and a half to three minutes. And when you start doing the math on that, you'd really like to get them to talk to you for four or five minutes. If you start having people talk to you for even six minutes and you've got six interview questions to ask, that's 36 minutes right there. Give yourself a little bit of time to actually ask the question, and you've eaten up 40 minutes. But if you go into that with 30 some odd interview questions, or 20 interview questions, you're going to get one or two minute kinds of answers, and that is just not long enough to reveal the truth about a candidate.