Brainstorming in a Case Interview: The Ultimate Guide

Last Updated on August 14, 2024

Brainstorming is a crucial part of any consulting case interview, regardless of whether you are interviewing with MBBs like McKinsey, BCG, and Bain, tier-2 firms, the Big 4, boutique firms, or in-house consulting divisions. It is a way for the interviewer to assess your ability to think creatively and structure your thoughts in a logical, MECE (Mutually Exclusive, Collectively Exhaustive) manner.

While it may seem daunting, with proper case interview preparation and the right approach, you can excel at brainstorming questions and impress your interviewer with broad, deep, and creative answers.

In this article, I want to dive deeper into this question type, similarities and differences in creating a case framework, thinking techniques, evaluation criteria, and communication tricks.

Brainstorming vs. frameworks

Brainstorming questions are similar to consulting framework questions at the beginning of a case interview in that both aim to structure your thoughts on a topic. However, while framework questions are often broad and open-ended, usually at the beginning of a case interview, where you develop your analytical lens to investigate the situation, brainstorming questions are more specific and require you to generate ideas to address a particular problem or opportunity, usually at a later stage of the case.

Both frameworks and brainstorming questions test your structuring and both can be investigative or prescriptive.

Investigative questions require you to explore a problem and come up with potential causes and solutions, while prescriptive questions require you to recommend a course of action based on a set of facts and assumptions. Brainstorming in consulting is very common in a daily project context, which is also why it is evaluated during the case interviews.

Framework question example

Case scenario: You are consulting for a startup that aims to launch an innovative electric scooter designed for urban commuters in Europe. The CEO seeks your help to determine the potential market size and key factors that will influence the company’s success.

Framework question: “Given the scenario, what factors would you analyze to accurately estimate the market size for electric scooters in European urban centers, and how would these factors influence the company’s strategic planning?”

Brainstorming question example

Case scenario: The same startup is looking for innovative marketing strategies to promote its electric scooter in highly competitive urban markets.

Brainstorming question: “What creative marketing ideas do you have to effectively launch and promote the electric scooter in urban European markets, considering the unique challenges and opportunities of sustainable urban mobility?”

Elements of a great brainstorming answer

A great answer to a brainstorming question should be broad, deep, MECE, and insightful. Developing innovative brainstorming ideas for consulting case interviews involves covering the problem fully and having enough ideas that support each top-level bucket in two or even three levels of granularity. It should also be based on hypotheses that are tailored to the current situation in the case and include creative ideas on top of more commonsense and standard ones.

The interviewer might ask you:

What reasons can you think of that would lead to machines breaking down in different intervals at different locations?

Investigative brainstorming question

If we look at the sample answer above it is:

• Broad: Covers the problem from multiple angles
• Deep: Breaks each top-level down into several sub-buckets and even more concrete ideas below
• Insightful: While some ideas are commonsense, others are more creative
• MECE principle: The problem is covered and there are no overlaps

A bad answer on the other hand is one where the candidate immediately yells out ideas in no particular order or structure, neglecting interdependencies and forgetting to bucket their ideas. This is bad both in terms of problem-solving and communication.

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Idea generation techniques for brainstorming

Best practices for brainstorming sessions in consulting interviews include the necessity for practice to become comfortable with idea-generation techniques. Explore effective brainstorming techniques for consulting cases in several ways.

Top-down brainstorming

Sometimes, you might want to think about a brainstorming answer in a more top-down manner, starting with the top buckets, and then expanding into lower-level ideas. This is useful when you want to use more concrete examples that could support a top-level bucket.

Bottom-up brainstorming

Other times, it might be easier for you to go and create your answer bottom-up starting with more concrete ideas and then aggregating it into a more general top-level bucket. Most often, you will likely combine both approaches for the same answer.

There are several consulting brainstorming techniques you can use to generate ideas for a brainstorming question to come up with an exhaustive and creative answer:

1. Mind mapping: Start with a central idea and branch out to related ideas.
2. Linking of ideas: Look for connections between different ideas and build on them.
3. Expansion of ideas: Take an idea and explore it in more depth to generate additional ideas.

Using a combination of these techniques can help you come up with a more diverse range of ideas and improve the quality of your answer. Let’s look into one example for each based on the following prompt:

“Think about ideas to revive a snack manufacturer.”

Mind mapping example

Central Idea: Launching a New Healthy Snack Brand

• Branch 1: Product Variants
  • Organic ingredients
  • Gluten-free options
  • Vegan options
• Branch 2: Marketing Strategies
  • Social media campaigns
  • Collaborations with fitness influencers
  • Free samples at local gyms
• Branch 3: Distribution Channels
  • Online direct-to-consumer sales
  • Partnership with health food stores
  • Subscription boxes for healthy snacks

Linking of ideas example

Initial Ideas:

• Eco-friendly packaging
• Community wellness programs

Linked Idea: Launch a community wellness program that encourages recycling and rewards participants with products in eco-friendly packaging. This links the concept of sustainable practices with community health initiatives, creating a comprehensive brand image focused on overall well-being and environmental responsibility.

Expansion of ideas example

Initial Idea: Implement a referral program to increase product sales.

Expanded Ideas:

• Offer tiered rewards to encourage multiple referrals (e.g., discounts for the referrer and the referred, free products after multiple successful referrals).
• Incorporate a social media challenge that leverages the referral program to increase visibility and engagement.
• Develop a loyalty app that tracks referrals and rewards, adding gamification elements to encourage ongoing participation.

Combination example

Let’s also briefly look into how we can combine all thinking techniques by thinking about the following prompt:

“Think about ways to make a city more liveable.”

Starting with the central idea of improving public transportation in a city, mind mapping could identify branches such as sustainability, efficiency, and accessibility. Linking ideas could then connect sustainability with electric buses and efficiency with real-time tracking apps, while expanding on accessibility might lead to exploring more diverse routes and better support for disabled passengers. This process ensures a holistic approach to brainstorming, covering multiple aspects, and digging deeper into each area for comprehensive solutions.

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By engaging in consistent consulting case practice through our course and drills, you’ll gain the proficiency and confidence required to adeptly navigate the complexities of case interview structures, ensuring you can effortlessly generate and structure ideas under pressure.

Approach to brainstorming in a case interview

To excel at brainstorming questions in a consulting case interview, it is essential to have a structured approach. I would always follow the same approach as for any other structuring or framework question, consisting of four steps:

1. To start with, it’s important to understand the question properly, so if you’re unsure, paraphrase the question back to the interviewer and ask for confirmation.
2. Once you have a clear understanding of the question, politely ask for some time to think about it. In McKinsey interviews, you have around 2 minutes to think, and in candidate-led interviews around 1 minute, sometimes even 1.5 minutes. If you take less time, you will not have enough ideas (being broad and deep), not enough creative ideas (being insightful), and no structure (no top-down and structured communication). During this time, you need to come up with your structured list of ideas, combining the thinking and idea-generation techniques I described above.
3. After creating your MECE structure, present it top-down, starting with the main areas and then going deeper into each bucket, discussing the ideas on the lower levels that support the main buckets (numbered, signposted, and top-down).
4. Discuss what you would want to prioritize or what idea you think is the most likely/best (based on the case) and automatically highlight how this integrates into the case as a whole and where to go next.

During the conversation, if the interviewer provides any feedback, try to integrate their ideas into your structure and build on them. Remember, the interview is a conversation, and it’s essential to engage with the interviewer and be open to feedback. Interviewers might ask “What else?” or steer you in a particular direction “Have you considered X?”

Interviewers might also probe if you are demonstrating knowledge of the relevant industry and the client’s situation, whether you are making connections between different pieces of information provided in the case, whether you are presenting their ideas confidently and convincingly, and whether they are proposing feasible solutions that align with their hypothesis or hypotheses in the context of the case.

Communicating your brainstorming answers

Finally, discover tips for structured communication in consulting interviews, pivotal when presenting brainstorming answers.

Effective communication is pivotal in consulting interviews, showcasing your consulting interview skills, especially when presenting brainstorming answers. One of the most powerful frameworks for structuring and communicating complex ideas is the Pyramid Principle. Developed by Barbara Minto at McKinsey & Company, it’s a technique designed to help consultants structure their findings and recommendations in a clear, concise, and actionable manner.

Utilizing the Pyramid Principle in consulting case communication is powerful for structuring and conveying complex ideas. Here’s how to apply it to your brainstorming answers:

The Pyramid Principle

The Pyramid Principle advocates starting with your conclusion or key message (the “top” of the pyramid), then supporting it with grouped arguments or categories (the “middle” layers), and finally providing evidence or further details for those arguments (the “base” of the pyramid). This method ensures that your listener grasps the most critical information first, followed by supporting data that makes your case more compelling.

For the sake of the brainstorming answer, you have your top level with the broad, general ideas, the middle layer with a further breakdown of these ideas, and the bottom layer, with the concrete and specific ideas.

Discussing the top level

1. Top-level buckets: Begin by outlining the main categories or themes of your ideas. These are your top-level buckets. For instance, if your brainstorming question is about increasing revenue for a retail company, your top-level buckets might include “Expand Product Lines,” “Optimize Pricing Strategy,” and “Enhance Online Presence.”

2. Number each idea: When presenting your top-level ideas, number each one. This helps in tracking the discussion and makes it easier for your interviewer to follow along or refer back to specific points.

Diving Deeper

1. Second layer for the first top-level bucket: Once you’ve outlined and numbered your top-level ideas, dive into the details of each. For the “Expand Product Lines” bucket, discuss specific strategies like “Introducing Eco-Friendly Products” or “Partnering with Local Artisans.” This second layer offers concrete examples and strategies that fall under the broader top-level category.

2. Third layer details: For each strategy in the second layer, provide detailed and concrete ideas that support its viability or success. For example, under “Introducing Eco-Friendly Products,” you might mention “Eco-Friendly Product Materials” and “Eco-Friendly Packaging.”

Repeating the process

1. Move to the next top-level idea: After thoroughly exploring the first top-level bucket, including its second and third layers, move on to the next idea, “Optimize Pricing Strategy.” Repeat the process of detailing and providing concrete ideas.

2. Continue until all buckets are covered: Proceed with this structured approach until you’ve discussed each top-level idea and its underlying layers. This method ensures that your answer is not only comprehensive but also organized in a way that’s easy to follow and understand.

Prioritize

1. Highlight the best way forward: Tell the interviewer how you would prioritize your ideas based on sound logic and business judgment.

Applying the theory and practice in interviews

Theoretical understanding: Familiarize yourself with the technique of Pyramid Principle communication before your interviews. Understanding the theory behind structured communication will help you apply it more effectively.

Practical application: Practice applying this method to various case questions. For instance, take a mock case question and draft your brainstorming response using the Pyramid Principle. Practice numbering your ideas and diving into the subsequent layers for each. Over time, this will become a natural way for you to organize and communicate your thoughts during actual case interviews.

By mastering the art of structured communication through the Pyramid Principle, you ensure your brainstorming answers are not just creative and comprehensive, but also delivered in a way that resonates with your interviewers, showcasing your analytical prowess and strategic thinking in a better light.

Tips for practicing brainstorming for a case interview

1. Get feedback from others: It can be incredibly helpful to practice brainstorming with a partner or group and get feedback on your structure and ideas. This can be a fellow candidate, a coach, or even a friend or family member who is willing to ask and listen. Make sure to ask for specific feedback on what worked well and what could be improved.
2. Use real-life examples: One way to improve your brainstorming skills is to practice with real-life examples. Take a news article, case study, or business problem and try to come up with a structure and ideas for how to solve it. This will help you build your industry knowledge organically and develop a more nuanced understanding of how to approach different types of problems.
3. Embrace creativity: While it’s important to have a structured approach to brainstorming, don’t be afraid to think outside the box and come up with creative ideas. Sometimes the best solutions come from unexpected places. Challenge yourself to think beyond the obvious and consider alternative perspectives. In doubt, the number of creative ideas that you can come up with is always more important than the way you bucket them.
4. Work on isolated drills: Instead of always looking at full cases, rather focus on isolated drills for each element of the case. This is also true for brainstorming questions. Take a set of 5-10 brainstorming questions and go through them one after the other, also practicing the communication aspect, not just the thinking part. This approach is much more effective than full case drills if you only want to work on one aspect, as it allows you to jump quickly from problem to problem and see a lot of problems in a short amount of time. This not only improves your idea-generation muscle to go broad, deep, and insightful but also your structured communication skills.
5. Practice under pressure: In a consulting case interview, you’ll likely be under time pressure to come up with a structured and insightful answer. To simulate this environment, try practicing brainstorming questions with a timer and see how quickly you can come up with a quality answer. This will help you build your speed and efficiency while still maintaining a high level of quality.
6. Optimize your note-taking: If you only have 1 minute to write down your answer, use shortcuts in writing (e.g., Profit = P) to maximize the time you spend thinking rather than writing. On top of that, become comfortable with creating ideas on the go. My experience shows that on average a candidate has 70-80% of their answer ready when they start talking. They figure out the remaining 20-30% once they start presenting their answer.
7. Reflect on your performance: After each practice session, take some time to reflect on your performance and what you can do better next time. Did you struggle with generating ideas? Did you have trouble structuring your answer clearly and concisely? Use this feedback to improve your approach and build your skills over time. You could create an error or issue log with problems you struggled with or just general answers to typical brainstorming questions. For instance, there are three core ways to increase customer satisfaction (1. decrease waiting times 2. increase service level or product quality 3. decrease price). If you have used this once, you can use it again and tailor it to the specific question (e.g., airline passengers would have different lower-level buckets than guests in a restaurant). Memorized brainstorming answers do not work, the same as memorized case frameworks.

Avoid common mistakes and pitfalls in brainstorming

Below is a table summarizing the most common mistakes and pitfalls I have encountered with my clients during brainstorming questions:

Avoiding these common mistakes and being aware of these pitfalls can significantly improve the quality of your brainstorming sessions in consulting interviews, showcasing your ability to think critically, creatively, and strategically.

Frequently asked questions around brainstorming

1. How does brainstorming differ from framework questions in case interviews? Brainstorming focuses on generating specific solutions to a problem, while framework questions involve creating an analytical structure to explore the case broadly.
2. What makes a brainstorming answer “broad” and “deep”? A broad answer covers multiple aspects of the problem, and a deep answer provides detailed insights into each aspect, including several layers of granularity.
3. Can you give examples of investigative and prescriptive questions? Investigative: Identifying reasons behind declining sales. Prescriptive: Recommending strategies to increase sales.
4. What are MECE principles, and why are they important in brainstorming? MECE stands for Mutually Exclusive, Collectively Exhaustive. It ensures that ideas are not overlapping and all possible areas are covered without gaps.
5. How should one structure and communicate brainstorming answers according to the Pyramid Principle? Start with the key message, support it with main categories, and provide detailed evidence or further details for those categories, ensuring a logical flow.
6. What techniques can enhance idea generation in brainstorming sessions? Techniques like mind mapping, linking of ideas, and expansion of ideas can generate a diverse and creative range of solutions.
7. What is the role of creativity in brainstorming for case interviews? Creativity helps in generating unique, innovative solutions that stand out and address the problem effectively beyond conventional approaches.
8. How does practicing with real-life examples benefit brainstorming skills? It builds industry knowledge, helps in understanding various problem-solving approaches, and enhances the ability to generate relevant, impactful ideas.
9. How do I identify when to use top-down vs. bottom-up brainstorming? Use top-down when you have a broad understanding of the topic and need to organize ideas into categories. Use bottom-up when you’re starting with specific details or solutions and need to cluster them into broader themes.
10. What are some effective strategies for quickly generating creative ideas during a case interview? Practice lateral and divergent thinking and apply analogies from different industries or situations to spark new ideas.
11. How can I practice the Pyramid Principle outside of case interviews? Apply it in everyday communication, like emails or presentations, by starting with your main point, followed by supporting arguments, and then providing details or evidence.
12. How do I effectively incorporate feedback from the interviewer during the brainstorming process? Listen actively, acknowledge the feedback, and seamlessly integrate it into your ongoing analysis or pivot your approach if the feedback significantly alters the direction.
13. How do I balance between depth and breadth in my brainstorming answers? Ensure you cover a wide range of ideas (breadth) but also select a few to explore in greater detail (depth), showing you can think both broadly and critically.
14. What role does industry knowledge play in brainstorming, and how can I improve mine? Industry knowledge helps tailor your brainstorming to be more relevant and practical. Improve it by reading our industry cheat sheets, and industry reports, following trends, and analyzing case studies within target sectors.

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