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Part 2: Preparing for Your Case Interview to Get Bulletproof

August 1st, 2009 Leave a comment Go to comments

So far in the “PhD’s Guide to Getting a Consulting Job,” we’ve covered how to work on your personal brand and write a resume that will get you an interview. Now, it’s time to get bulletproof for the interview itself.

Case interviews are an interview tool that consulting companies use to gauge your analytical skills. Essentially, the case interview involves answering an open-ended question about a business problem. The interviewer gives some background on a (hypothetical) company that needs help. Then the candidate talks through an analysis and solution.

I’m going to show you how to rock a case interview.

The interviewers are looking for a few things in particular in a case interview:

  • Structured thinking
  • Hypothesis-driven approach
  • Strong analytical ability
  • Creative problem-solving skills
  • Keen business sense
  • Composure in the face of pressure and uncertainty

McKinsey-style Cases Vs. Normal Cases:

Some firms use “McKinsey-style” cases to make the interview more fair and relieve some pressure. These cases are more structured and give the applicant three or four specific questions to answer. “Normal” cases, on the other hand, give a problem statement and expect the applicant to direct the entire case with little or no guidance from the interviewer. It is a good idea to practice both, as they each teach different skills.

You can find good resources and sample cases at the Georgia Tech Consulting Club site.

Things to Remember

If you read some of the material available, you’ll get lots of advice. These are the 5 things that I think are most important.

  • Structure Everything. EVERYTHING. Instead of jumping right into an answer, start by outlining your answer to the interviewer. First, describe high-level “buckets.” Next, discuss each one in turn by listing lower-level items within each “bucket.” Think trees. You should give an overall framework for solving the case and separate frameworks for estimation problems, math problems, data analysis, final recommendations… EVERYTHING. The more you structure, the better you’ll look.
  • State Your Hypothesis. Never ask the interviewer for information or start making analysis without specifying what you’re attempting to prove (or disprove). You can demonstrate that you are “hypothesis driven” by stating your hypotheses out loud and saying how you plan to evaluate them. This sentence would be a good example, “I would guess that competition is a key driver of the low price because widgets are a commodity. Can you share any information on the competitive landscape to help me confirm that?”
  • Back up Assumptions. You’ll often be asked to make assumptions. Partly this is to see if you make reasonable guesses. However, always make educated guesses and then specify how you could go about collecting the real information if needed. For example, “I’d assume 25% of personal automobiles are trucks based on what I see driving around. Of course, I could check that by looking at industry sales numbers. Does 25% sound like a reasonable estimate for now?”
  • Ask “So What?” Every time you reach a number, conclusion, or stopping place immediately ask yourself, “So what?” Then answer out loud to the interviewer. Don’t say, “It will cost $2 million.” Instead, say, “It will cost $2 million, which is [surprising, disappointing, expected, etc.] considering…” By stepping back and answering “So what?” without being prompted you show that you can grasp the big-picture. And you’ll make an impression.
  • Nail the recommendation. The last thing you’ll do in a case is “give your final recommendation.” Nail it by being direct and decisive. Have the first words out of your mouth be what the company should do. Cite a couple of reasons why, give one or two caviots, re-state the recommendation and stop. Whatever you do, don’t summarize the case to the interviewer… they were there! They know!

How to Practice

You can build up your case interview skills before you ever practice a case with someone else. However, you should definitely get some mock-interviews under your belt before your real interview. Here are 3 ways to practice. 2 you can do solo, the other you need a partner for.

1. Structure Drills

This drill will help you get your “initial structure” handled. This crucial step can make or break a case, and if you do it right, you will be off to a great start. The secret is doing this enough that it becomes second nature.

Read the case intro. Start by finding a case (try looking here). Read the intro paragraph describing the case, but nothing else. Don’t look at any additional information yet.

Work for 10 minutes. Brainstorm and write a detailed tree-shaped structure for approaching the case. Your final tree might look something like this. However, yours should be more detailed, and tailored to the specific case you’re working with.


Keep the structure MECE (mutually exclusive and completely exhaustive). This means that each category is independent from the others, but together they cover all possible areas needed to analyze the case. Edit your structure until you feel that it is as good as it can get.

Improve your structure. Read the rest of the example case and re-evaluate your work. Did you leave anything out? Would a different structure have made more sense in light of the new information? Edit and improve your structure-tree again. Note any revelations that may help you next time.

Practice presenting it in 30 seconds. In the interview, you’ll have about a minute to prepare a structure and then 30 seconds to present it to the interviewer. You want to start with a bang, so make sure you practice presenting it OUT LOUD. Start by saying the top-level items and then going into specifics for each. Make sure you convey which top-level item you hypothesize is the most important and why.

Do this drill over and over until you are a case-structuring-machine!

2. Creativity Drills

Interviewers sometimes ask for you to come up with “some ways to cut costs,” or “some new ways to market the product.” These questions are meant to test for creativity and out-of-the-box thinking. To some extent, this has to do with how your brain works. But it you can still warm up and get in the habit of thinking creatively.

As you go through your day, come up with creativity-prompting questions. If you stop for coffee ask yourself, “how could they get me to pay $0.25 more per cup.” When you get groceries ask yourself, “what are some ways this grocery store could cut costs.” By doing this all the time you’ll get in the habit.

Make lists of 10, 20, 50 things. One way to coax out creativity is to number a page (or open a spreadsheet) and commit to making a list of 10, 20, or 50 creative answers to some of the questions you came up with during the day. Don’t worry about “good” or “bad” ideas, just make sure you get to your number-goal. You’ll be surprised how inspiring that big empty list can be.

3. Mock Cases

Practicing by yourself is necessary to hone certain skills, but nothing compares to sitting across the table from a friend to do some simulated interviewing. Here are a few tips on making the best of practices.

Find good people to help you. The best choices are people who are currently working at the firm you’re applying to. The next best choices are people who have been through these types of interviews. Be careful about how you use these peoples’ time. Don’t use your best resources until your skills are sharp from practicing alone and with less experienced friends.

Be serious throughout the entire mock interview. Don’t joke around just because it’s your friend and it’s “only practice.” Ask your partner not to pull any punches. The stress helps you learn. You want a practice that is as close as possible to the real thing.

Share feedback right after the interview. The interviewee should start off by giving their impression of the case. Even if you’re case skills need work, it is important to make sure your “interviewer” sees the same problem areas as you do. When the “interviewer” gives feedback, take notes and ask questions. This is probably the best information you can get on how to improve.

Leave questions or other preparation ideas in the comments.

Next: Experience Interview

Now you know how to practice for your case interview. Don’t forget:
Part 3: Talking about Your Experience and Sounding like a Bad-ass, which covers an important and often overlooked portion of the interview… talking about yourself! I know you have some amazing stories to tell; learn how to make them say the right things about you.

Disclaimer: I recently went through the application and interview process with a top firm, came out with an offer, and signed it! In this series, I share my experience and give some ideas for people on a similar path. However, at the time of writing (July 2009), I do not have any inside information on how any company conducts their hiring. These are just my thoughts!

  1. Matt
    August 1st, 2009 at 18:39 | #1

    Hi there,

    I’d recommend the “Case in Point” Cosentino book, which has been recommended to me numerous times, and with which I know many people (including myself) successfully practiced for job interviews at consulting firms like BCG, McKinsey, etc.

    I’ve had a brief look at the “Ace the Case” serie, which seems fine but I didn’t practice with it. Also, McKinsey, Bain and others offer online example of case interviews.


  2. August 1st, 2009 at 23:06 | #2

    Great comments. “Case in Point” is a good resource, but overused IMHO. The McKinsey and BCG websites have great info.

    I refrained from suggesting “Case in Point” directly because many people that I’ve helped prepare have *memorized* the book. That’s a mistake. It’s clear when a person is gives canned “case-in-point” answers, and it is a turn-off. The book has its place, but use it sparingly ; )

    The case prep resources on the McKinsey and BCG sites are *awesome* though. You should definitely check those out… especially if you’re planning to interview with one of those companies… They tell you *exactly* what they’re looking for in the interview!

  3. Matt
    August 2nd, 2009 at 06:47 | #3

    True, I like the cases in Case in Point, but the idea is to get used to the *thinking* process, and I certainly wouldn’t recommend anyone to learn it by heart! Also, there might be a gap of popularity of this book between the US and Europe ; )

    Anyway, great resources from the Georgia Tech Consulting Club, thanks!
    Another interesting thing to know: some consultancies actually organize mock cases workshops, sometimes by free registration (and then selection, of course), sometimes organized by some biz-school alumni within the firm. However, it’s not always easy to find out about these events, and I haven’t found a single website that was putting together the details of such events for all top consultancies. Any idea?

  4. October 1st, 2011 at 17:23 | #4

    You can use RocketBlocks.me to prepare for your cases – it’s an online web app that specifically helps students prepare for the cases by drilling them on the exact types of questions that come up (from structuring case problems, to doing mental math to anayzing charts)

    Instead of memorizing case structures like Case in Point teaches it forces you to practice structuing, brainstorming, math and all the aspects that are critical to a case.

  5. Casey
    January 29th, 2015 at 09:37 | #5

    I agree: Marc Consentino’s Case in Point is sort of a must for aspiring consultants, but of course you shouldn’t resist the temptation to memorize everything.
    Preplounge.com is very similar to rocketblocks.me but has the advantage that you can meet up and practice with case partners.

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