How to be MECE in a Case Interview

Last Updated on November 20, 2024

Consultants at McKinsey, BCG, and Bain utilize the MECE concept to define a method that helps them to think through problems and organize information. It helps them to be efficient and clear in their problem-solving process.

Consequently, candidates that go through the case interview process with the top firms need to demonstrate they are able to think through problems and situations in a MECE way as well. In this article, I want to

• discuss what it means to be MECE and become an effective problem-solver
• provide you with some examples of MECE frameworks
• show you why it is important to be MECE and what happens if you are not
• highlight the most common errors I have seen in more than 1,000 interviews (for you to avoid)

What it means to be MECE

MECE stands for “Mutually Exclusive and Collectively Exhaustive.” It refers to a method of organizing information and problem-solving in which you separate information into categories that are mutually exclusive (non-overlapping) and collectively exhaustive (complete). This means that all information is separated into categories that do not overlap and that together, the categories cover all relevant information.

This approach is used to ensure that no important information is missed and that all possible parts of a problem are considered. In consulting case interviews, the ability to provide MECE structures is relevant both for case frameworks and brainstorming.

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Example of a MECE analysis in a business context

According to the MECE concept, you need to grasp your options by categorizing them into groups to comprehend and resolve any significant issue. Let us look at one example from the business world where that might be relevant:

One example of a MECE framework that is used by companies is a market segmentation analysis. This framework involves dividing a market into different segments based on characteristics such as demographics, behavior, and needs. The segments are mutually exclusive, meaning that a customer can only belong to one segment, and collectively exhaustive, meaning that all customers are included in the segmentation.

The segments can be:

• Demographics: age, income, education, etc.
• Behavioral: usage rate, brand loyalty, etc.
• Needs-based: benefits sought, usage occasion, etc.

For example, a company might segment its customer base by age, income, and behavior. The segments might include:

• Young, low-income, and casual users
• Middle-aged, high-income, and loyal users
• Elderly, low-income, and occasional users

This framework allows the company to identify specific target markets and develop tailored marketing strategies for each segment, which can increase the chances of success.

Why is it important to be MECE in a case interview?

At the start of every case, you need to create a structure, which is the roadmap of your analysis. Being MECE in a case interview is important for five reasons:

1. Clarity: MECE frameworks help to organize information and make it more clear and more understandable, making it easier to identify key issues and opportunities.
2. Completeness: By ensuring that all relevant information is captured and that all possible solutions are considered, MECE frameworks help to avoid overlooking important details and ensure that the analysis is comprehensive.
3. Efficiency: By breaking down a problem into smaller, manageable parts, a MECE framework allows the interviewee to focus on specific areas and avoid becoming overwhelmed by large amounts of information, i.e. “boiling the ocean”
4. Problem-solving: A MECE framework allows the interviewee to structure the problem-solving process, making it more logical and efficient. This can help to identify the root cause of a problem and generate potential solutions.
5. Communication: MECE frameworks can help to communicate complex information clearly and concisely, which can be useful in a case interview where the interviewer is looking for clear and logical thinking.

Therefore, in a case interview, utilizing a MECE framework can help the interviewee structure the problem-solving process, make the analysis more comprehensive and efficient, and communicate complex information clearly and concisely.

What happens if you do not structure a problem in a MECE way?

If a case interview problem is not structured in a MECE way, it can lead to several problems:

1. Confusion: Without a clear and organized structure, it can be difficult to understand the problem and identify key issues and opportunities. This can make it harder to generate potential solutions and evaluate their feasibility.
2. Incompleteness: Without a comprehensive analysis, important information and solutions may be missed. This can lead to a lack of understanding of the problem and can make it harder to develop effective solutions.
3. Inefficiency: Without a structured approach, it can be easy to get bogged down in large amounts of information and become overwhelmed. This can lead to a lack of focus and can make it harder to identify the root cause of a problem.
4. Poor problem-solving: Without a logical and structured problem-solving process, it can be difficult to identify the root cause of a problem and generate potential solutions.
5. Poor communication: Without a clear and organized structure, it can be difficult to communicate the problem and potential solutions clearly and concisely. This can make it harder to convince the interviewer or other stakeholders (in a real client setting) of the validity of the proposed solutions.

Therefore, not structuring a business problem in a MECE way can lead to confusion, incompleteness, inefficiency, poor problem-solving, and poor communication, which can make it harder to understand the problem, develop effective solutions, and communicate them effectively.

All these issues would likely lead to rejection by the top firms.

Example of a MECE analysis in a case interview

The most common framework that you will encounter in your case interview preparation is a profitability framework. Let’s have a look below.

Three principles help you come up with a MECE framework

1. Covers the problem fully: Revenue and Cost are the two drivers of Profit, hence our framework above is Collectively Exhaustive
2. Considers all elements: The framework prevents overlaps in the analysis, thereby being Mutually Exclusive
3. Is tailored to the problem at hand: This part is often forgotten. You need to tailor your framework for the specific industry or problem you are dealing with. For instance, if we are talking about the airline industry, the Price would be a combination of things such as ticket price, booking fees, seat allocation fees, onboard dining fees, duty-free fees, airport fees, etc.

The common errors that I see with frameworks that are not MECE

I have seen and heard more than 1,000 frameworks and brainstorming answers over the years and there are a couple of common issues that candidates struggle with when trying to create a MECE framework.

Let’s think through an example:

What areas would you look at to reduce CO2 emissions with our shoe manufacturer?

Typical case problem at MBB

Certain elements overlap

The framework won’t function properly if things appear more often than once. Think about areas that might show up multiple times throughout your framework.

For instance, if you break the problem down from a process perspective, you might look at it from five steps: 1. Suppliers, 2. Transportation 3. Production, 4. Transportation, 5. Sales.

While this covers the problem fully, you have an overlap about Transportation, which leads to an unintentionally non-MECE framework. Always double-check your approach and eliminate overlaps.

If you move into the lower levels of the framework, you might want to consider the Materials that you purchase from Suppliers as one bucket to investigate. Many candidates then also consider Materials again in the Production bucket, again creating a non-MECE framework.

You get the idea!

You are missing crucial elements

A framework must encompass the entire group to be considered comprehensive.

To stick with our example and your approach from a process perspective, you want to take into account all steps of the process. If you end with Transportation, you are missing a crucial area of the problem, which relates to the Sales process (think about CO2 reduction related to stores, online shopping, returns, etc.

Elements need to be on the same level of the hierarchy

When possible, MECE classification categories should be directly comparable if they are on the same level.

If one of your top-level buckets is Production, another top-level bucket cannot be “Analyze our delivery fleet” as the latter is a much more concrete area to look at (which would fit as an idea below the Transportation bucket)

Your elements contain logical errors

MECE-ness is not the only thing you need to think about when creating a case interview framework or brainstorming about a problem.

For instance, many candidates reply with buckets such as Customers or Competition to the question above, which does not answer the question at all, yet still might be a MECE distinction in itself. Being MECE does not shield you from all errors or misconceptions you might encounter.

Frequently asked questions

Here, we’ve compiled a list of insightful questions that delve deeper into the nuances of the MECE framework, a cornerstone of problem-solving used by top consulting firms like McKinsey, BCG, and Bain. Whether you’re a novice in the world of case interviews or looking to refine your approach, these questions and answers aim to shed light on common challenges, practical tips, and advanced strategies for effectively applying MECE in various scenarios. From balancing detail and breadth in your frameworks to adapting your analysis in real-time during an interview, this section is designed to enhance your understanding and application of MECE, helping you to stand out in your next case interview.

1. How do you balance between being overly detailed and too broad in creating MECE frameworks during a case interview?
2. Can you provide examples of non-MECE frameworks and discuss why they fail?
3. How does one adapt their MECE framework in real-time during an interview if they receive new information or feedback from the interviewer?
4. Are there industries or types of business problems where applying MECE is more challenging, and how do you navigate these situations?
5. How can candidates practice or improve their ability to think and structure problems in a MECE way outside of case prep?

1. Balancing detail and breadth in MECE frameworks: To maintain balance, start with broad categories and drill down where necessary. Prioritize areas with the highest impact or relevance to the case question. It’s also helpful to follow the interviewer’s cues; if they show interest in a particular area, it may warrant more detail. Practice simplifying complex ideas without losing their essence, and use judgment to decide when further division of categories adds real value or just complexity.
2. Examples of non-MECE frameworks and their shortcomings: A non-MECE framework might categorize market segments by age, income, and then again by a combination of age and income, leading to overlaps. Another common mistake is incomplete frameworks, such as analyzing a company’s performance by looking at revenue but omitting cost factors. These frameworks fail because they either provide redundant information or miss out on critical aspects, leading to inefficient problem-solving and potential oversight of key insights.
3. Adapting MECE frameworks in real-time: If new information arises during an interview, acknowledge it and assess its impact on your existing framework. If the information opens up a new category or reveals an overlap, adjust your structure accordingly, either by integrating the new data into existing categories or creating a new one. Stay calm and show your logical process to the interviewer; they are interested in your adaptability and logical structuring more than a perfect initial framework.
4. Applying MECE in challenging industries or problems: In complex industries or with multifaceted problems, applying MECE can be challenging due to the interconnectedness of factors. In these cases, focus on the core objectives of the problem and build your framework around these objectives, ensuring each category remains distinct. For highly interconnected areas, consider using a layered approach, where you first broadly classify the elements and then dissect the interrelations in a controlled manner within each category.
5. Practicing MECE thinking: To improve MECE thinking, engage in daily practices such as categorizing items or concepts in your environment or current events into MECE groups. Practice cases from various industries and problem types to apply MECE in diverse contexts. Reflect on each practice session by identifying what was MECE, what was not, and why. Engage in discussions with peers or mentors to challenge and refine your structuring skills. Lastly, consume content critically by always looking for the underlying structure and thinking about how you would organize the information MECE-wise.

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