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Category: Case Interview Mastery for McKinsey, BCG, Bain
The most pertinent MISTAKES which lead to failure during MBB interviews
Written by Dr. Jörn Kobus on Jul. 7th 2022
There are certain “patterns of weakness” which have emerged from our experience of interviewing hundreds of candidates for McKinsey and BCG over the years. HEre is what should be avoided at all costs during MBB interviews.
Throughout the last decade, especially as interviewers of McKinsey and BCG, we have seen hundreds and hundreds of MBB candidates who were NOT successful in their interviews with the world’s top consultancies. And the truth is, that there are thousands of possible reasons for failure. 
No candidate is rejected just for ONE particular mistake.

"(...) one math mistake and you’re dinged!” 

is just the usual nonsense which you get when asking random people on the internet for advice.
However, what is also true is that no candidate is rejected just for ONE particular mistake. So this myth of, e.g., “one math mistake and you’re dinged”, is just the usual nonsense which you get when asking random people on the internet for advice (and unfortunately you even get this sort of advice from the gazillion inexperienced junior consultants who became coaches in the space ☹).

An exception to the above is, when you show behaviors which lead to questioning your integrity or value system - like lying to your interviewer for example.

That being said - of course there are certain “patterns of weakness” which have emerged from our experience with candidates over the years.
For the sake of simplicity and clearness, let’s segment these mistakes into 4 areas and then provide you a couple of examples to make them tangible for you:

  • Top 3 mistakes which occur throughout the entire interview
  • ​Top 3 mistakes which occur during the Fit Interview part (applies to BCG/Bain and most Tier-2 consultancies like Strategy&, Oliver Wyman, Roland Berger, EY Parthenon etc.) 
  • ​Top 3 mistakes which occur during the Personal Experience Interview (PEI) part (applies to McKinsey only)
  • ​Top 3 mistakes which occur during the Case Interview part

Top 3 mistakes which occur throughout the entire interview

  • Taking on an oral exam mindset: An interview at MBB should be a mutual discussion! It is NOT an exam, where you are asked specific questions by a professor or examiner, for which you have to find the specific “correct” answer. The interview at MBB is a conversation. It is a conversation which serves the purpose to demonstrate who you are as a person, and also to demonstrate the relevant qualities which you possess. Many candidates completely overlook this aspect - and the consequence is a very undynamic behavior, where the candidates are very tight, and guided by fear of giving a “wrong” answer, instead of really showing what they have to offer.
  • ​Displaying low energy or a lack of enthusiasm: Nobody likes to talk to energy drains! Make sure that talking to you is a pleasant experience. Bring a healthy amount of energy to the table, project an open body language, and communicate in an engaging way. This includes, for example, emphasizing certain parts of your sentences while you speak (according to which messages you actually want to emphasize).
  • ​Inability to communicate top-down: In board level strategy consulting (as this defines what the top Level consultancies are doing), very few things are as important as structured thinking and communication. Consultants are requested to present recommendations to their clients crisply. Because their clients are busy executives. Many times, they only have a few minutes to communicate that recommendation. What senior clients expect from them is to deliver their communication in the form of a short and clear main message or recommendation. Then, if interested, the client will ask for details. This is called “top-down” communication (or it is also sometimes referred to as the "Pyramid Principle"). And this is what candidates need to show in an MBB interview at all times.

Top 3 mistakes which occur during the Fit Interview part (BCG/Bain and most Tier-2 consultancies) 

  • Shallow answers to the question “Why consulting” and “Why our firm?”: A typical example is if a candidate fails to outline his/her own career objectives, and how consulting in general, and the respective firm in particular, would be a great platform to achieve these objectives. Essentially the question here is about how you can frame your “motivation to join” in a transparent, honest and appealing way. It is just not enough to tell the interviewers about how great your team will be or that you are looking to grow fast or that you just love project work and you will see many industries in a very short time. This is what literally(!) everybody speaks about - so please do not believe you stand out in that way.
  • ​ Perceived dishonesty: I don’t mean necessarily plain lying here, but coming across as not entirely genuine. For example, coming up with fake weaknesses when asked something like “what are development areas that you see for yourself?” or “what are your weaknesses?”. And then some candidates come up with an extremely shallow or superficial answer that is often even trying to imply that your weakness actually is a strength (like, "I am such a super detail orientated person"). And some people make up stuff - which then is plain lying. Please don't. Just don't. Because making up stuff will backfire. Senior interviewers have years of experience and have seen hundreds and hundreds of candidates - so they sense this usually fast. And in addition, this is really a values' issue.
  • ​Projecting a wrong attitude towards the job: This can obviously span across multiple sub aspects, for example asking about “What are the kinds of projects with the lowest working hours?”, or asking about “how many free days do I get per year?”, or also asking about perks such as Hotel points or First Class travel, free food ordering, etc. All of this does not tend to come across very positively as you might imagine and bluntly speaking, is really(!) dumb to do. This might be more or less important for you individually but there is simply no room in your interview for this.

Top 3 mistakes which occur during the Personal Experience Interview part (McKinsey)

  • Selecting weak examples from your past: For most candidates it might not make sense to use instances of academic excellence as examples for Entrepreneurial Drive (the only exception is if this is REALLY an outstanding achievement, i.e. something that nobody in your university has ever achieved). Otherwise, there is a pretty big risk that this is seen as too “normal” by the interviewer who might think “well, every single candidate has to be excellent academically in order to even sit here in this interview - that doesn’t differentiate that candidate from ANYONE else who I interviewed today”. 
  • Inability to cope with deep dives and follow-up questions: Many candidates fail to cope with the really extreme deep dives and follow-up questions related to their stories. Interviewers often go to extreme depth in order to really understand the reasons, WHY a candidate did something or why the candidate said something. Many candidates do not understand that the core of what they need to transport is not even so much WHAT they did, but WHY they did it! Having no strong answers to these questions is a frequent source of doubt that then emerges in the mind of the interviewer - and this then oftentimes leads to a rejection. Because the WHY is really the decisive factor for finding repeatability in the everyday life of a consultant. In essence you could say: “one excellent WHY can produce an unlimited number of excellent WHATS”. Let me repeat this, because it is so essential: “one excellent WHY can produce an unlimited number of excellent WHATS”
  • Not focusing on what you personally did: Pretty often, candidates shift into a mode of telling their stories in terms of “yeah and here is what WE then did to address the problem…”. While literally every single candidate knows that this should not happen, it still happens often ☹ And this is just a mistake! Because even in a team setting, your story ALWAYS needs to focus on what YOU specifically did to help the team overcome a certain obstacle or challenge. Don’t get me wrong - this might very well include you involving others! However, you still need to clearly outline exactly what YOU did, and how YOUR actions and YOUR words either complemented what others did, or even provided GUIDANCE to the people around you. Cause this is what the interviewer needs to hear from you.
The unfortunate truth is - that you likely will have little idea if your stories are meeting the bar or not if you have no senior calibration for these. However, in whatever the circumstances, please make absolutely sure to take your preparation for the PEI as serious as you are preparing for your case interview performance! The evaluation from both, the PEI and your case interview will be decisive for wheter you end up getting an offer or not.

Top 3 mistakes that occur during the Case Interview part

  • Weak conceptual thinking: Well obviously - failure to derive structural elements from a clear logic and a missing link to the core question is NOT something that will serve you well. Very often, candidates misunderstand that structuring a case does not just mean to come up with buckets and sub-aspects, which they just need to list. A “framework” is NEVER, NEVER a structure. Candidates have to make clear how they will answer the question that has been asked. If they fail to do so, they are perceived as “guessing around” and just looking into several buckets randomly - just hoping to stumble upon some interesting information that will then guide them towards the right path - instead of analyzing with a plan. You need to avoid being perceived as such a "weak conceptual thinker" at all cost. I repeat, AT ALL COST. By the way, this is the same when asking for data... So if it is common for you to use phrases like "do we have any information on cost, or do we have any information on the market, or do we have any information on revenue" - you'll probably not gonna make it.
  • Lack of generating “so whats”: One classical problem that candidates have is that, after having dived deep into specific analyses, and even having correctly derived the specific value for a certain metric they were looking for, then they triumphantly emerge and declare: “Alright - the result is 328!”. And then..............................................................................… SILENCE. This is the moment, when the interviewer (at least with his/her inner eye), really raises eyebrows. Because what is expected from the candidate is NOT to just spit out a number! Remember - you have to behave in a client friendly way throughout the entire case. Throughout the entire interview actually ;). So spitting out a number alone is completely meaningless for a client. You don’t treat clients like that! Once you have finished the calculation, you relate the result back to the case question. At a very minimum, you have to at least explain what this “328” actually means. So this is one of the most critical elements of adequate “process discipline” when navigating through cases. Again..., nobody, not even your interviewer is primarily interested in the solution to the case presented. They are looking primarily if you are of a top problem solver, which means that you can solve ANY case question, not only the presented one. Make sure you show that...
  • Failure to take the interviewer along: Unsuccessful candidates frequently make the mistake of expecting interviewers to essentially read their mind. Some examples: They don’t share what they think, they don’t share their logic, and they do not lead the interviewer through the case. Or they come across as extremely disorganized. They are “drowning in data” and are losing focus to show what ACTUALLY needs to be answered in order to arrive at a recommendation; and this is often even amplified by losing track of their own notes and confusing numbers, and confusing units. This is a really weak performance. And by the way it is also completely independent of whether the end result that the candidate then reaches is “correct” or not! Even if it is correct - it is still a weak performance. As already mentioned, the interviewer needs to be treated as a client and deserves (a) process transparency, and (b) result clarity. Hence, you have to walk the interview through your logic and align on this logic. Then you perform the calculations while TAKING ALONG the interviewer. This is how you would also ensure buy-in from a client. Because walking the client through the analytical steps instead of just presenting a result is how you ensure buy in. And this(!) is what interviewers are testing for when they discuss cases with candidates.

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About the author: 
Dr. Jörn Kobus

Former Senior Engagement Manager and Interviewer at McKinsey & Company

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About the author: 
Dr. Jörn Kobus

Former Senior Engagement Manager and Interviewer at McKinsey & Company

About the author: 
Dr. Jörn Kobus

Former Senior Engagement Manager and Interviewer at McKinsey & Company
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