Case Interview 101

There are 4 stages of learning anything, including Case Interview:

  1. Don’t know that you don’t know
  2. Know that you don’t know
  3. Know that you know
  4. Don’t consciously know that you know

So simply searching for stuff we don’t know is not enough. There are things we don’t know that we don’t know. Too bad this is what many of us do to prepare for Case Interview. We need a one-stop place that gives us a big picture. That’s exactly the role of this page. We won’t go too much into the specific content here, but this should act as  a “home” and a “map” page for your case interview studying no matter where you are.

For beginners who don’t know where to start…

… This video is a must-see video that touches on the must-know basics and fundamentals.

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I still remember the first time I heard about “Case Interview”. I remember feeling excited, then quickly getting lost on where to start. Hearing people speak about some useless concepts with no idea of what they are, how they were related, or where they fit into the big picture?

Well, later I realized that those concepts were not that mysterious at all. It is just that nobody had done quite a good job teaching me in a structured and top-down way.

In this article, I will try to be that first somebody to help those who are in the same predicament.

(See also: Consulting Interview Prep – How to prepare for Consulting Cases; How to avoid getting stuck in cases?)

Hi, my name is Kim Tran. I am a former McKinsey consultant and the founder of the platform Management Consulting Prep. The insights I am about to share with you are the results of years of experience in both management consulting and in case interview coaching. I have coached hundreds of candidates of various backgrounds … from the brightest students of Harvard, Wharton to some real “newbies”. Regardless of background, many don’t have a good grasp of Case interviews basics.

In this article, I will show you Case Interview through the eyes of an absolute beginner. We will encounter many new concepts along the way. This will ensure that you can learn these concepts in an intuitive way and still see the big pictures and how those concepts relate to each other.

 

1. WHAT IS CASE INTERVIEW?

In the broadest sense, a Case Interview is like a normal job interview with business content involved. By doing this, companies can have a better idea of how well a candidate thinks, analyzes, and works through business problems. For more on this topic, read the Bain post on case interview.

 2. WHAT DOES THE FORMAT LOOK LIKE?

Each company uses a slightly different case interview format. But for the scope of this video, we will focus on the most common format that the Big 3 – McKinseyBCG, and Bain – use. That is the 1-on-1 format with no case data revealed before the actual interview.

To better illustrate the concept we just discussed, here is a typical example of a “business problem” in a typical case interview at McKinsey, BCG, and Bain:

“Let’s say we have a restaurant called “In-and-out Burger” with recently falling profits. How can you help?”

The case interview will be a working session between the interviewer and the candidate to solve that business problem. During this process, the candidates’ skill sets will be demonstrated and evaluated.

3. WHAT IS EVALUATED IN A CASE INTERVIEW?

In a Case Interview, the final result is not as important as the process. In other words, the interviewer will judge whether you work through the business problem in the “right way”, regardless of whether or not you solved it correctly.

This is because consulting firms believe that if a candidate has a good methodology, he or she can consistently solve many other business problems, whereas a lucky candidate who solves a case using a rusty approach may not be able to solve future cases.

So what is the “right-way” to solve cases? There are several components to this.

  • No.1: A good method will look for the root cause of the problem, not just the symptoms on the surface.

For example, if a patient is having pain in his chest, a “non-root-cause” approach would be to provide some medications, whereas a “root cause” method would be to run tests and see what is really causing the chest pain and cure it. So simply put, look for the root cause!

Now that we know we have to find the root-cause, the next thing is to make sure that we can identify ALL root-causes. That leads us to:

  • No.2: A good method will break down the big problem into smaller pieces in a MECE  way.

3.1 MECE

MECE stands for “mutually exclusive and collectively exhaustive“, which in simple language really means 2 things.

  • 1st: the small pieces of those big ones cannot overlap (this is “mutually exclusive”). For example, a non-MECE way to break down the student body of a course is: Group 1: international students and Group 2 Female students. These 2 groups do overlap. Some international students can be female.
  • 2nd: those small pieces all added together has to equal the big problem. For example, a non-MECE way to break down the student body of a course is: Group 1: students from China and Group 2: students from the United States. These 2 groups combined do not necessarily equal the total student body.

In this example, some MECE ways to break that student body down are: Male and Female or International students and Domestic students.

Now back to the original story, we were discussing the 2nd component of a good method in case interviews, which is to breakdown any big problem into smaller pieces in an MECE way. What would that look like in the “In&Out” example?

  • Here is a bad method:

    Could the declining profitability be due to weak management? Increase in competition? Increase in beef costs? Or shift of customer tastes? While all of the these can very well be the root cause, that’s not a MECE way to break down the big profitability problem. There are some overlaps and no guarantee that all possible root causes are listed.

  • Here is a good method:

    The declining profitability is either caused by (a) decreasing sales revenue or (b) increasing cost! Then within each branch, we can break it down further. Now you may wonder how we consistently do this. What is a good way for always breaking down big problems in the proper form? This leads us to the next concept: Case Interview Frameworks.

3.2 Case Interview Frameworks

In simple language, a Framework is like a pre-set template that candidates can use to breakdown frequently-seen business problems or cases.

By using frameworks, you can be certain that your approach is always structured and MECE.

Some of the most popular frameworks are:

  • Profitability framework (used for profitability cases)
  • McKinsey M&A framework (used for Merger & Acquisition cases)
  • Porter’s Five Forces (used for Market Entry cases)
  • Other’s like 4C, 4P, etc. frameworks (used for other general cases)

You will find more detailed information on Case Interview Frameworks in other videos and on our website.

Come back to the big picture. Now that we can break down the problem in MECE ways, we have to find the root-cause fast! The No.3 component of a “good method” is to appropriately prioritize which small piece to delve into. This leads us to the next concept: Hypothesis.

3.3 Hypothesis

Hypothesis is an educated guess of where the root cause might be, and therefore, going into branches that are more likely to contain the root cause.

Hypotheses should be based on information provided in the case.

So to summarize, a good method to approach a business problem has three components:

  • No.1: Look for the root cause and solve it, not just the symptoms
  • No.2: Look for the root cause by breaking down the big problem into smaller pieces in an MECE way
  • No.3: Use hypothesis to prioritize pieces that most likely contain the root cause.

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4. WHAT IS THE COMMON FLOW OF A CASE INTERVIEW?

The flow of a case interview differs among interviewers and firms. To easily visualize this, let’s imagine a spectrum where the two ends represent two types of case interviews.

On one end, the interviewer rarely intervenes, and the candidate will lead the approach, from structuring the problem, drawing frameworks, asking for data, to solving the case. This is referred to as the “Candidate-led” case.

On the other end, the interviewer controls the process in significant ways. He or she has the candidate work on specific parts of the overall problem and may help out on structuring the case. This is referred to as the “Interviewer-led” case.

Most case interviews fall in the middle of this spectrum. So distinguishing the two types of case interviews only matters in the preparation process.

5. WHAT DOES IT TAKE TO DO WELL IN A CASE INTERVIEW?

Based on my experience, this is probably one area that most candidates don’t realize, leading to unbalanced and insufficient preparation for interview days.

So to answer the question, there are three equally important factors that decide whether you get the offer or not.

  • No.1: How good you are with Consulting Math, numbers, and quantitative ability.
  • No.2: Is what I refer to as Case Interview “Tips and Techniques“. This includes a wide variety of habits, from showing your structured mindset, saying the right things, asking for timeouts at the right times, getting clarifications, to even organizing your notes. Certainly, these are skills and habits that are learnable if one has the right materials and a good study plan.
  • No.3: Is your Business Intuition. How insightful and creative you can be in various business contexts. A candidate insufficiently prepared for this is very much like a basketball player without physical strength and athleticism. No matter how skillful he is, he can’t compete well. Of the three factors, this is probably the hardest and it may take the longest time to prepare for.

To help you improve on those three aspects, I have developed the comprehensive End-to-end program. What I ask of you is to take every single element of this program very seriously. Trust me that I have put so much thought and effort into it and it’s there for good reasons.

6. NOW WHAT?

If this is actually your very first case interview lesson, you may be wondering what are some of the next steps you should take for your study.

  • Step 1. See or read some sample case interviews in action to connect what you learn in this video with a real demonstration. You may find this in our later videos, on consulting firms’ websites, or in various other prep materials. No need to do a mock case interview at this point. It can be very frustrating and discouraging if you haven’t got the basics yet.
  • Step 2. Develop the habit of reading business publications to improve your business intuition. The earlier you start doing this, the better. There are many good sources of business publications, but I strongly recommend those from McKinsey, Bain, and BCG.
  • Step 3. Get started with your Math practice. Again, the sooner the better. Visit our Consulting Math Questions section for more information.
  • Step 4. Learn those Tips & Techniques. See our other videos and articles for the right materials and study plan.
  • Step 5. Only at this point should you do a mock case interview. Do it, reflect, study the area you don’t feel comfortable with, then go back and do a few more mock cases and keep the cycle going on.

I hope this has been a good first lesson on your case interview journey. If you have any questions or comments, please leave them below. This will allow us to develop content that better suits your needs.

Thank you for reading, and don’t forget to share this with your clubs and friends if you think this article is helpful for them as well.

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