How to Structure a Case Interview


Thanks to your videos I made it to the final rounds, but the feedback from the last interview said that I needed more structure.

As you surely know, case interviews at McKinsey (at least in my country) are pretty standard in structure. This structure is as follows:

1. They open with a business situation, ask you to come up with areas to investigate.

2. They ask a more specific question, based on what you said at 1.

3. They give a numerical analysis and ask for conclusions.

4. Overall conclusions and recommendations.

Some steps may repeat during a case, for example instead of 1 2 3 4 it may be 1 2 3 2 3 4. My point is that you don't really drive the case, they ask you questions which you have to answer.

Which brings me to my question.

For my last case I had a wine producer that we had to asses for a private equity buy out. So, for 1 I set up your standard framework, and after we went through it, the interviewer jumped to the question : "What are the dimensions in which this firm can grow?".

I asked what he meant by dimensions, but he restated the question. So, the first thing that popped into my mind was market share. He didn't agree, but did not tell me right away (I found out at the end of the case).

He asked what else, so I said increase products and products output. We moved on to 3 and 4 which went well, and that was it.

He told me that I need more structure, because for example at the dimensions growth question, I should have said that market share is an objective, not a dimension, and that he wanted to hear a MECE list like : Increase products, increase product output, grow geographically etc. They gave me 2 weeks, one already passed, in which I should practice this structuring.

So, my question is, in this case study interview standard, how can I practice for gaining MECE structuring capabilities in just one week?

They said I should find a partner (which I have already been doing, but having in mind a case situation like you described) to do some mock interviews, although they don't conduct the interviews the standard way (in which I drive the case, not them). So, I ruled out their suggestion, and I came to you for help.

My Response:

Your situation/question has several aspects to it.

First, the frameworks are a useful way to START a case. You will want to listen carefully to your interviewer as they will often guide you in a different direction if your initial approach is wrong.

For example, I have in the past started a case with the business situation framework but then switched to a supply/demand framework. Other times I'll start with one of my standard frameworks and then make up a new framework on the fly (an advanced skill only needed in perhaps 1 in 15 cases).

Second, when the interviewer asked about dimensions for growth, what I think he/she meant was what WAYS can this company grow? I personally wouldn't have used the term dimensions as an interviewer, as the average person doesn't know what that means.

If you did not understand the question, you really should not proceed until you do. The reason the interviewer probably repeated his question was he didn't want to give you the answers (like introduce new products, target new market, etc..)

But you could have re-phrased the question to confirm if you understood the vocabulary. So I suspect if you said something like, "Are you asking me which WAYS this company can grow?" "Is that what you're asking?" He  would have probably said "yes" (which doesn't end up revealing any of the potential answers).

It also sounds like he wasn't looking for an overall business assessment, but was looking specifically to analyze the various ways the target company can grow. This makes sense particularly in the case of evaluating an acquisition.

They key to making an acquisition work is to see if the acquiring company can find a way to grow the target company that the previous management team did not or could not execute.

The other reason the interviewer might have done this is perhaps he (I'm just going to assume he for ease of writing) worked only on the revenue growth aspects of the actual client situation. And perhaps someone else had taken the competitive and industry aspects of the client situation.

So the interviewer only had data for the portions of the case that he worked on... and thus wanted to guide you in that direction because in any other direction he wouldn't have had the background to answer your questions / requests for data.

Also it looks like in this case, the team or interviewer used more of a revenue - costs = profits framework. As in: what are the revenues and costs under current management versus what would the potential revenue and costs be under the acquiring company.

This is a different framework and certainly isn't wrong.. but it does organize the information in a different way.

It seems to me that the interviewer really wanted to talk only about revenue growth opportunities and nothing else.

When this situation comes up where it doesn't fit a pre-existing framework perfectly, it is often useful to give a high level answer organized in a way that is easy to follow. This is the "more structure" the interviewer was likely referring to.

Most people who answer the question "what ways can this company grow" will say something like this:

1) They could grow through X method.....

Interviewer: Okay, what else?

2) They could grow through Y method....

This is very much like a laundry list and is very hard to follow. It is like reading a text book that has no table of contents and no chapter titles... it's very easy to get lost. Thus you need to "structure" your answer a bit up front before diving into the details.

To use an analogy, you need to state the table of contents before you dive into the details of each chapter.

Or to use a different analogy, when you give a speech, you want to say, "In my speech, I will talk about 3 topics: Topic A, Topic B, Topic C" (notice the similarity to a framework).  Then in your speech you talk about topic A, then you say, "As I said at the beginning, I am going to talk about 3 topics: A, B, C. I've just finished topic A, now I'm going to talk about topic B."

So basically you want to list all your answers to the question, "In what ways can this company grow?" up front BEFORE you dive into exploring any one answer.

Now there are many ways a company can grow. To list all of them in detail would take up way too much time. So you'd ideally want to list the major categories of growth.

This is where the MECE Principle comes into effect. You want to use the MECE principle to organize your initial answer.

So one possible answer would be...

"Let's see, you want me to find all the various ways this company can grow. Let's see, in general to grow a business you can change what you sell (e.g., new product vs. old product) or change who you sell to (existing customer/customer segment vs. new customer/customer segment)."

I probably would have listed this as a 2 x 2 matrix which is a more STRUCTURED way to present this kind of information... as it presents it in a visual way that is more easily understandable to more people than describing it verbally, which I am having difficulty doing:

Old Customer Segment New Customer Segment
Old Product
New Product

This an example of a MECE framework in that in each dimension, there is no overlap in each of the categories and when you add up all the categories, it covers 100% of the possible options within the category. (Click Here for more info on MECE framework).

While consultants are fond of "MECE-ness," sometimes "MECE-enough" is good enough... particularly if there isn't a better way to organize the information at hand.

For example, another possible way of organizing the answers to "what ways can this company grow" could be:

  • Products/Services - Existing vs. New
  • Customers - Existing vs. New
  • Distribution Channels - Existing vs. New

This approach has some structure to it, but it's neither mutually exclusive ("ME") or collectively exhaustive ("CE").

You could improve it by using the following approach:

  • Products/Services - Existing vs. New
  • Customers - Existing vs. New
  • Distribution Channels - Existing vs. New
  • Other Ways to Grow*

The last category is a catch-all.... so a client (or in your case an interviewer) can never say your framework didn't cover every possibility.

By adding the "other" category, it makes the work collectively exhaustive (the CE part of MECE), but there is still the potential for overlap across the three primary areas - products, customers and distribution channels.

In practice, as consultants we often use MECE-enough approaches when a clean MECE approach doesn't come to mind. The same approach is reasonable in a case interview. However, before you get tempted to use a MECE enough approach, take the effort to consider if you can make your approach 100% MECE first.

In terms of practicing how to create MECE ways to organize information (e.g., frameworks) on the fly, you can practice this very easily by using the MECE in everything you do in everyday life.

"Hi honey, here are all the ways I love you:

Section 1: Qualities about you that I love

Section 2: Qualities about me that I love when I with you

Section 3: Other

"Where should we go to dinner tonight?"

Here are our options:

1) Restaurants East of our current location

2) Restaurants West of our current location

3) Restaurants North of our current location

4) Restaurants South of our current location


1) Restaurants within a 1 mile radius

2) Restaurants within a radius of 1.01 miles to 2.0 miles

3) Restaurants within a radius of 2.01 miles+

This may seem ridiculously "STRUCTURED" to the point of being really absurd in everyday life... but believe it or not, this is how consultants think. You may now want to use the approach out loud in a social setting, but many consultants will think in this way in their heads.

You can see examples of cases being structured in the Look Over My Shoulder® audio recordings.

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