What Interviewers Notice in a Consulting Case Interview


So I wanted to ask you - in terms of how one presents oneself and the mental approach to interviews, what is it you looked for in candidates during your time at McKinsey?

My Reply:

Case performance aside, I typically found it reassuring when I found someone who was good at the cases and liked doing them.

I had one candidate who was I think a Physics PhD from IIT, the MIT of India, and he was ranked #1 in the country or something like that.

He was miserable in my interview and clearly not enjoying himself. Now it's true he wasn't doing well, but I have seen candidates who were not doing all that well but were still enjoying the process.

They didn't pass the case interview test so-to-speak, but they did tend to pass the "airplane test" -- as in do I want to sit next to this person on an airplane every week for three hours.

A lot of candidates are very stiff and nervous in the interview. Even in the mock interviews I did for Look Over My Shoulder®, I could tell some people were very nervous.

The problem with being overly nervous is its harder to think clearly. A little case of the nerves is fine, but too much impacts performance both analytically and socially.

Now if someone did really well on the case, but the seemed miserable, I would probably notice it, wonder about it, but still pass them to the next round just to make sure it wasn't just me. So this wasn't technically a hiring requirement, but more of an observation.

I will say that amongst my colleagues at McKinsey and friends at other firms, those who did well in consulting, progressed in consulting, were often the same people who enjoyed the interview process.

Those who quit consulting after six months (I knew a few who did), were competent at the case interview but did not love it or even like it.

I found myself looking forward to the case interviews because I always learned something new each time.

And just today, I got a note from a new client who spoke to some previous clients of mine, and the remark all the previous clients made about me was that I was very curious... as in very curious why a certain kind of customer exhibited a particular kind of buying behavior, and so on... So I guess that's just a part of me.

So this was a long winded answer to your question (and a few you didn't ask), but to make a long story short:  enthusiasm + analytical, was always a great combination to see in a candidate.

For more resources on case interviews, review my free video series on Case Interview Secrets .

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4 comments… add one
  • Ryan Oct 6, 2012, 7:25 am

    Hi Victor, your articles are great and I find them really useful in my preparation for interview.

    I just had an interview with a mid tier firm but have yet to receive a reply. The interviewer gave me a market estimation question on the amount of money required daily in an ATM machine. Well, I started off with the complicated way by calculating the number of buildings, offices, people etc. around the vicinity of the ATM and other “standard operating procedures”. In the end, I came up with a huge number which is not realistic. Although I do mentioned that it is not realistic, I did not manage to do it the way the interviewer wanted, and he guided me along to his answer, which was to calculate the average time need by a person to withdraw money and also the utilization rate.

    What I am puzzled about is that, if the interviewer knew that my approach was wrong in the first place, why did he still lead me along that path? I was explaining to him about my rationale behind having certain assumptions and he agreed and even gave me suggestions. May I know what was he looking for exactly when doing that?

    Thank you!

    • Victor Cheng Oct 6, 2012, 8:10 am


      In terms of your approach, the error you made falls in the category of choosing the incorrect proxy. In my book Case Interview Secrets, I have a chapter on the underlying methodology for estimations. The key to getting an estimation “right” is to choose the proxy with the highest correlation with the number you are trying to estimate.

      You took the approach of trying to estimate demand. The interviewer took the approach of trying to reverse engineer demand by looking at constraints on supply (e.g., the machine can only be used by one person at a time and it takes a finite mount of time per use).

      Neither approach is inherently wrong or right all the time, its a judgment call as to which approach is simpler, more accurate, and more likely to be correlated with the actual number.

      In terms of why the interviewer let you run down a particular path that he or she disagreed with, an interviewer will do this for several reasons.

      1) Sometimes an interview would have personally taken a different approach, but if a candidate lays out an alternative approach this is well reasoned with fair assumptions, even though it is not the approach the interviewer will personally use, the interview can give full credit for the answer.

      In other words, often there is more than one way to be right. And rather than cut off the candidate they minute he or she provides an answer different than one right answer, sometimes we will let a candidate run with it to see where it goes.

      2) other times the candidate makes one flawed assumption early on, but perhaps the actually logic is good. In these cases, we’ll let the candidate go with it to see if it was just one initial flaw that was a problem, but everything was flawless or to see if multiple mistakes were made along the way.

      If a candidate made a small mistake early, especially where the final answer was highly sensitive to that initial decision, BUT the rest of the approach was sound AND it is a first round AND the candidate resume is strong, personally I would pass the candidate, give them some feedback to fix what I would perceive as an imminently fixable mistake and let the interviewer in the next round make the hire / no hire decision.

      If there are multiple errors in the rationale, then my bias would be to not pass the candidate on the idea that the gap would be too large to close within the time between this and the next round.

      3) Sometimes a candidate will take the wrong approach, recognize the approach is wrong (especially if it is recognized fairly early down the wrong path), and self correct to a better approach. In my book, again in earlier rounds, I would pass such a candidate.

      On client engagements, sometimes consultant do take the wrong path. It happens all the time. But often it is not obvious it is wrong until we get more data. So one key skill is how quickly does one recognize the mistake and self correct. So it is possible the interviewer wanted to see if you could self correct.

      Your clear recognized that your estimate was off, but it sounds like you didn’t provide or didn’t have time to provide an alternative approach.

      Hope this helps demystify what the other side is thinking.


  • Ryan Oct 7, 2012, 1:00 am

    Hi Victor,

    Thank you so much for the reply: it has been most helpful. By the way, this was the final round of interviews. Just like what you said, I felt that the interviewer did not give me enough time to rethink about my approach after I did a sense check on my estimate. He just went straight on with his approach and I was pretty much following what he said after that. At the end of the case, I even asked him to further explain his rationale for having certain assumptions and he was kind enough to draw it out on a paper. This was something that I was not sure if I did it correctly. Did it mean to him that I was not on the same page as him? Do interviewees generally ask their interviewers to explain their approach?

    I just checked with a friend of mine who did the exact same question as me with the same interviewer a month ago. He approached the question the same way as I did, with the interviewer explained to him the same approach that he told me, and my friend ended up not getting an offer. So I guess this pretty much predicts my outcome as well.

    O well, I really need more practices! Thank you Victor!

    • Victor Cheng Oct 8, 2012, 7:16 pm


      Generally if you’ve gone all the way until the end of one approach before realizing the approach wont work, most interviewers won’t give you a chance to correct. But if you go down a path for say 5 minutes, and say woops, I should really go this way instead, most interviewers would be okay with that and if the candidate ended up solving it correctly, most interviewers would pass the candidate.

      In terms of interviewers explaining their approach, that will just vary by both interviewer and how much time is available. Keep in mind the time constraint is very important because 80% of the time there is another candidate following you and they want to stay on schedule.


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