I’m not interviewing for the right answer to the questions I ask. Instead, I want to see how the candidate thinks on their feet and whether they can engage in collaborative problem solving with me. So I always frame interview questions as if we were solving a real-life problem, even if the rules are a little far-fetched.Eric Ries, author of The Lean Startup*
The best interview questions are short and clear. Short and clear questions ensure candidates answer the question you meant, not just those they’ve previously thought about and are primed to respond to.
Good interviewers use a balance of open and closed questions. Open (or “open-ended”) questions, such as “How would you approach that challenge?”, allow the candidate to determine the direction of the discussion and show how they handle ambiguity. Open questions do not have a yes, no, or otherwise simple answer. Closed questions have specific answers, such as “How many months did you spend on this project?” These questions are good for gathering basic facts or seeking clarification.
Interviewers may need to probe into ambiguous or obfuscated answers, which are often signs that the candidate either doesn’t know the answer or is trying to hide something (perhaps avoiding an admission of fault, in a behavioral interview). Ambiguity requires specific or direct follow-up questions.
Sometimes a candidate may say something that just doesn’t make sense given the context shared in the interview. For example, they may describe previous work experience in a way that sounds problematic to the interviewer, but the candidate doesn’t acknowledge the problem. This sometimes happens because the candidate may not recognize that they’ve left out key context or details. This situation requires further questions, even leading ones, to clarify whether the candidate behaved correctly but just failed to communicate clearly during the interview. Any time a possible exculpatory explanation exists, a good interviewer will pursue it to avoid later questions about whether their assessment was correct.
Eric Ries stresses, “No matter what question you’re asking, make sure it has sufficient depth that you can ask a lot of follow-ups, but that it has a first iteration that’s very simple.” This gives you the opportunity to probe further into what the candidate may or may not know. Ries distinguishes between degrees of “not-knowingness” that give you additional signal:
The candidate doesn’t know, but can figure it out. Perhaps it’s been some time and they can’t recall all the details, but they have a strong intuition that leads them in the right direction.
They don’t know, but can deduce it given the key principles. If you fill the candidate in on the basic rules, can they reason from there? Would that change the way they approach the problem at hand?
They don’t understand the question. Ries notes that “Most questions require a surprising amount of context to answer. It doesn’t do you any good to beat someone up by forcing them through terrain that’s too far afield from their actual area of expertise.” If it is their area of expertise, you know you’ve hit a point to consider in your evaluation. If it’s not, it’s best to move on—it’s not fair or efficient to ask them to keep struggling through at that point.