Read part two here

“Ok, your client is a large, multi-national…”

This opening sentence is enough to strike fear into the hearts of many talented MBA graduates. Case interviews with firms like McKinsey, BCG and Bain can be a daunting proposition.

MBA job candidates getting ready for case interviews prepare extensively. They read books. They watch video tutorials. They do a ton (sometimes hundreds!) of mock interviews with friends and peers. This instinct, to prepare diligently for the upcoming interviews, is well intentioned but flawed because candidates always forget two critical things:

Case interviews test a basket of skill sets To succeed in a case interview, you must excel at demonstrating those skill sets

Unless you clearly enumerate the skills needed, and appropriately build your capability in each, you won’t be able to prepare successfully! Say you’re learning to ski for the first time. You have two options. The first is jump on the chairlift, go to the highest peak and let ‘er rip. The second is to practice each of the fundamental skills needed in skiing: turning, stopping, stance and balance, using your poles and then try out an easy run.

The first option is just like doing a million mock cases without ever pausing and thinking deeply about the underlying skills. The second option is significantly better: you identify the skills, build them and then gradually start testing and refining them on the mountain.

Which skill sets matter?

It’s no secret that consulting firms hire top talent. But what does top talent mean? If you break down the interview process at firms like McKinsey, BCG and Bain, you’ll find that they consistently look for the same skills and they consistently fall into two key buckets: analytical skills and soft skills:

Analytical skills: problem structuring, charts and data analysis, mental math

‘Soft’ skills: communication, leadership, collaboration, personal drive

In this series, we’ll take a deep dive on each of these skill set areas and look at how they fit into the case interview.

Analytical: Problem structuring

Structured problem solving is often considered one of the superpowers of consultants: taking a big, hairy messy problem and breaking it down into manageable chunks. Once you decompose a problem into manageable chunks, resolving it becomes an order of magnitude easier.

As a result, every case interview begins with some sort of problem structuring challenge. This is a critical area of the case interview to process to practice. Not only is it a key skill, as we spoke about above, but it also sets the opening tone for the remainder of the interview. If you excel in problem structuring, you’ll be off to a great start since you’ll have a nice, logical framework to follow for the remainder of the interview.

The magic of MECE

Contrary to popular belief, the secret of problem structuring is not memorizing a stable of frameworks (e.g. profit = revenue - costs) that you can use for every problem type nor is it just falling back on the same popular frameworks (e.g. Porter’s 5 forces) over and over again!

The secret to great problem structuring is applying the MECE principle: mutually exclusive, completely exhaustive. This is superior because it’s a principle which:

Can be applied to any case problem Decomposes any case problem into logical, complimentary buckets

Let’s use a simple example to illustrate how this might work: say your interviewer asks you to help size the market for rental cars in the US. Your first instinct might be to think of all the use cases for car rentals: business trips, replacement cars for when yours is at the mechanic, foreign tourists needing cars, domestic tourists needing cars, etcetera.

One approach would be to enumerate all of the potential use cases and estimate each individually and then sum them up. However, there are downsides with this approach because it involves doing a lot of individual estimates. Additionally, what happens if you forget a critical segment? Your whole estimate will be off!

A better approach is to apply the MECE principle. Using MECE, you might consider all of those examples but look for mutually exclusive buckets to put them in. For example, all of the above examples could fit into business rentals and non-business rentals. Now you’ve got two top level buckets that are mutually exclusive and are completely exhaustive. This simplifies the whole problem, reduces the number of calculations you need to do and ensures you’ll get to a more accurate estimate.

Next steps

To recap, not all preparation for case interviews is created equal. Rather than jumping right in and doing tons of mock interviews, first consider the key skills in the consulting firms are looking. Second, start building your skills in each key area.

In the next post on this series, we’ll dive into the analytical skills around mental math and charts and data analysis. In the meantime, if you want to dig further into the MECE principle on problem solving, you can find a detailed write up on that here.

Kenton Kivestu is the Founder and CEO of RocketBlocks, an online platform that helps students prepare for case interviews. Prior to RocketBlocks, he worked as a strategy consultant in BCG's San Francisco Office, launched online ad platforms at Google and led the Zynga mobile poker franchise. He has successfully navigated hundreds of case interviews himself and believes that the case interview is an important recruiting tool that helps simulate the on the job experience.