Solving Problems with the MECE Principle

Cracking the case interview is the straightest path to a position in one of the top management consulting companies. It’ll take quite a bit of time, a lot of effort on your part, and most of all — knowing the MECE principle.

In this article, we’ll take you through the basics of what the MECE principle is, as well as provide you with some useful examples and actionable advice. By the end of the read, you will be able to tackle even the most challenging of issues using this approach and show you can think like a consultant.

What Does MECE Stand For?

There’s no point in proceeding any further until you understand what MECE stands for. It’s crucial to your proper use of the framework. 

MECE, or Mutually Exclusive, Collectively Exhaustive, is a principle that you can use to dissolve larger problems into smaller components. You do so by categorizing the problem into groups that are mutually exclusive (no overlap between the groups) and collectively exhaustive (every part of the problem can go into one of the groups).

For example, if you’re looking into a business trying to expand into a new geographical territory, creating only two categories, let’s say North America and Europe, will not suffice. The groups are mutually exclusive, but they’re far from being collectively exhaustive. What about customers from Asia, Australia, or any other part of the world?

The MECE framework will help you get the bigger picture and also ensure you’re not missing out on a crucial bit of information. And that’s something your interviewers will be on the lookout for among other things.


As you probably know, case interviews require that you solve some specific problem in a very narrow time frame. 

Business problems can range from completely banal (such as a drop in revenue), requiring a simple profitability framework to crack, to highly complex where MECE is a must.

The MECE framework is a problem structuring principle that consultants use to organize data comprehensively and efficiently. Using a systematic problem-solving framework such as MECE ensures you avoid unnecessary duplication and any potential overlaps or gaps in your reasoning.

Given the time constraints of a case interview, you can see how useful MECE is. You don’t want to waste the precious time your interviewer has given you by solving the same problem twice. Be MECE as much as you can, although sometimes, the time restraints won’t allow you to think of everything.

In that case, it’s best to focus on the ME part. Mutually exclusive categories are easier to achieve than the complete exhaustion of options. Not only that, if your categories overlap, you’re duplicating work and losing efficiency.

Practical Advice to Remember

It’s time we provide you with some actionable advice that you can use to be more MECE. Now that you understand what the principle is and why you need it, it’s important to put it to practice.

The Rule of Three

MECE doesn’t limit you to the number of categories you can create to solve a problem. That poses an issue on its own, since you may be tempted to create fewer or more groups than you need. 

Fewer groups mean less accuracy, while too many could be difficult to remember. Keep in mind that you’re at your case interview, the clock is ticking, and you’re under a lot of pressure. It’s easy to forget an item like that.

The Rule of Three states that it’s best to create three categories whenever possible. Three sets of items tend to be more memorable and optimal than any other number of groups or categories.

Of course, you won’t always be able to do that depending on what the issue is. But it’s a good rule of thumb. 

Represent the Whole Group

To achieve the CE part, that is to be collectively exhaustive, the whole must be the sum of all its parts. In this case, the sum of all groups.

Let’s say you’re analyzing students at a university. If you create groups for female and freshman students, you’re not representing all the students.

Always ask yourself if you’ve managed to cover the whole group. In our example, you’d either need to group students according to gender or the year of studies. Otherwise, you might fall into the trap of being non mutually exclusive.

Consider the Atypical

Let’s go back to our student example. Perhaps you’re interested in the activities the students are performing.

It might seem like a good idea to create two groups, one for indoor activities and one for outdoor activities. The groups seem mutually exclusive and exhaustive. But what about students that don’t do any other activities except being a student?

You have to think about the atypical examples such as that one if you want to be truly MECE.

Communicate in MECE

You can apply MECE principles in your communication as well. Your interviewers are going to notice that and value your conciseness.

We mentioned how the goal of the framework is to be efficient and to avoid duplication. The same goes for the way you communicate. Avoid redundancy as much as you can. Don’t beat around the bush without ever getting to your point.

Keep the communication clear and concise, ask structured questions, and make sure that the conversation is meaningful.

That way, you’re constantly practicing a MECE approach, and you’re signaling you have all the qualities of a consultant.

Examples of Non-MECE Segmentation

One excellent example that portrays the lack of mutual exclusivity is segmenting the cars into a color and a type of car. If you say that there are blue cars and SUVs, you’ll be duplicating work each time you need to analyze a blue SUV — once while analyzing all the blue cars, and once while going over all the SUVs.

On top of that, such categorization is not accounting for cars of any other color, or types such as sports cars, hatchbacks, or station wagons.

You can also try and group how a restaurant operates. You could make groups for walk-ins and online orders. But they’re far from being collectively exhaustive. What about calling a restaurant to place a delivery? How about drive-throughs?

The Bottom Line

MECE segmentation is already present in many of the most commonly used case interview frameworks. But those frameworks don’t account for unique and unusual cases, and there are far more of those than there are regular ones.

Learning MECE principles and understanding why they’re important will equip you to deal with any unforeseen business situations that the interviewers might throw your way. Know those principles to stay one step ahead, and you’ll be able to crack any case with ease.

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