How (not) to conduct a Case Interview

There are several books that advise students and busy professionals on how to prepare for a Case Interview. An excellent one is Case In Point. However, having conducted and been interviewed as a candidate several times in Case Interview settings over many years, I note that many interviewers tend to lack skill in conducting Case Interviews. This is sad, quite embarrassing and many a time a dis-service to the organization the interviewer works for. A poorly conducted case interview can hurt an otherwise worthy candidate's career prospects, and cost your company an attractive hire. If a Case Interviewer does a bad job, it is unlikely she will permit the candidate to advance even if he performed well given the interview constraints. The interviewer's ego will simply not permit it. And a candidate's protests are worthless since he'll be viewed as incompetent and disgruntled because he did not advance.

Of course, the most typical Case Interview setting still remains one where a prepared interviewer meets a not-as-well-prepared candidate, with both sides being prepared for the encounter being something of an exception rather than the rule. 

What happens when an unprepared Case Interviewer meets an unprepared Case Interviewee? This falls into the realm of questions like, "when a tree falls in a forest with no one there to hear it, does it make a sound?" And we ignore it in this post.

So what are some key "rules of thumb" for Case Interview interviewers? We present a brief, and not exhaustive list here in what follows:

1. Do your homework. Know the case question you are asking. Know it well. Know the context/setting, the problem, possible solutions, and paths to get there. Most importantly, know what "a correct answer" looks like.
2. Know what direction(s) you are willing to let the candidate take, guide him in those directions. Do not perform this function haphazardly, pushing one way and then another, because you yourself do not know how one should proceed from start to finish.
3. Scope the problem beforehand. You can have multiple objectives, but you must decouple them and ask the candidate to solve each piece first before going on to the next. Do not cut back and forth between multiple questions. This confuses both yourself and the candidate.
4. Know what questions you expect the candidate to ask, what data you want to present them when they do, and how you want to respond if they ask questions you did not anticipate.
5. Be reasonable with the case problems you make up. There has to be a way to get from your question or premise to an acceptable answer. Well prepared candidates can crack reasonable questions in half the time you think needs to be allotted. By the same token, if the question is poorly defined, or you base it on some vague idea in your mind, no candidate will be able to finish it in time.
6. Know what assumptions make sense, and which ones you are willing to accept. If the prepared candidate asks "I am assuming there are 300M people in the US, and the average life-span in the US is around 80 years, is that reasonable?". Feel free to say no, and ask for clarifications, but once you say yes, and the candidate does all the math based on these assumptions, don't backtrack 15 mins into the problem telling him the base assumptions are incorrect.
7. Last, but most important, do not penalize the candidate for your lack of preparation. If the "answer" the candidate comes up with, based on assumptions you approved earlier does not look right, gently ask the candidate to redo the calculations with more reasonable assumptions, but acknowledge that your approved assumptions were somehow incorrect.

The above are only some ideas on how prepared interviewers might conduct a Case Interview. Note however that there are exceptions to every rule. An interviewer is justified in breaking one or more of the above rules if she is conducting a "confrontational" or "hostile" interview to test the candidate's mettle in a final round. These are designed to see how the candidate handles pressure, uncertainty and difficult situations. But such interview scenarios evolving naturally (instead of deliberately) due to lack of preparation is unforgivable. Good interviewees spend many weeks of effort mastering the Case Interview technique. Hurting someone's career potential because you are unprepared is criminal. Do not conduct Case Interviews if unprepared.