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How can you brainstorm in a structured way during a case study interview?

brainstorming questions Case Interview Creative Interview MBB McKinsey MECE
New answer on Apr 29, 2020
14 Answers
28.1 k Views
Pedro Rueda
asked on Feb 15, 2017

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replied on Feb 15, 2017
MIT MBA | Bain & Co | Ex-Google | 4+ year coaching experience

Brainstorming creatively in a structured/MECE way when under pressure is one of the hardest things to do.

Let's have a look at a basic example: "how can client X gain market share?". A great start to answering the question would be; "Let's look at ways that X can do this in the long-term vs the short-term", OR "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 segment vs. new customer segment).". This way the interviewer can see that you have a structured mind and that you can also prioritise what really is important. Next, you would create yourself a table with Existing Product & New Product ( on the horizontal axis) VS Existing segment & New segment (on the vertical axis). Then, you start brainstorming ideas into each of the 4 boxes. This way, you will be able to come up with loads of things and the interviewer will be very happy with your structured mindset.

Other examples of dimensions that can be used to encourage structured brainstorming are:

  • Existing VS New (applies to customer segments, products, distribution channels)
  • Organic VS Inorganic (e.g. when thinking about growth)
  • Short-term VS Long-term (e.g. when making a decision that required direct implementation)
  • Internal VS External (e.g. when talking about operations)
  • Customer-focused vs Non-customer focused
  • Revenue-based vs Cost-based

Once you have gone through a few ideas and have structured them into sections/buckets it is good practice to select the best ones according to some parameter. For instance, select ideas which have high impact and high implementability. It is important to note that every case is different and so you must always put a lot effort into customising the answer and prioritising what is most relevant.

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Content Creator
replied on Feb 15, 2017
#1 Coach for Sessions (4.500+) | 1.500+ 5-Star Reviews | Proven Success (➡ | Ex BCG | 10Y+ Coaching

Great question Pedro; here are the things I would recommend you to do:

  1. Recap all the information till that moment. This will give you time without sounding you don’t know where to go.
  2. Always try to identify 2-3 key elements that would constitute the fundamental pillars.
  3. After having defined the key pillars, then start to brainstorm for each of them.

Bonus: you may ask for time after step 1 if needed, to think more on the appropriate structure to apply before brainstorming.

Let’s see a concrete example.

Interviewer: So, generally speaking, how would you decrease the cost of raw materials?

Step 1: Recap the situation

Interviewee: So, if I got it right, you would like now to move to the elements that could decrease this cost. If it is fine for you, I would like to do a small recap and then move through the key elements that can help to do so. At the beginning you asked me what brought a decline in profits. We have identified the problem lays in Product A, and in particular in the cost area. We then found out that the main increase in cost was related to raw material.

Interviewer: That’s right.

(Notice that you may have likely gained 30 seconds of additional time just summing up information)

Interviewee: Do you mind if I take 1 minute to think about it?

Interviewer: Please take your time.

Step 2: present the key pillars of the structure

Interviewee: Thanks; I believe there are two key areas to decrease the cost of raw material; we may decrease the cost of each unit, or we may decrease the number of units we buy. I would like now to go a bit deeper in these two components.

(Notice that even if you are brainstorming, you are first putting down a list of the MECE pillars of a structure. This is fundamental to brainstorm correctly)

Step 3: brainstorm elements inside each pillar

Interviewee: Well, in order to decrease the cost per unit we may do a couple of things, keeping in mind we want to maintain revenues at the same level: number one, decrease the quality of the units that we use; number two, negotiate with the supplier; number three, find another supplier.

In order to decrease the number of units, we may do two things; we may implement a more efficient method to use them, so that we would have to buy fewer of them. We may also substitute some of the units with something else that may be cheaper and with the same effect on the final product.

Of course, the best way to do correctly step 2 and 3 would be to have good structures already in place and/or have read a lot of cases, to backup your references.



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Anonymous replied on Apr 29, 2020

Hi Pedro,

I would generally recommend you to structure your brainstorming. Simple 2by2 matrix might help you. So, if you can provide an initial framework, which you would like to brainstorm, in the very beginning, it would be helpful just to settle down your brainstorming. And then, you would be able to communicate it.

Just to give you an example. Let's brainstorm according to the value chain on the options. So we start with research and development, brainstorm on these topics, continue with supply, then with production, then with sales and marketing and then with after-sales.

This is typical framework, which you can use in brainstorming.

Hope it helps.


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replied on Aug 07, 2017
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School



Here is how you should answer these questions:

1) Ask an interview for a minute to think

2) Think of several buckets of ideas (e.g. scope / value proposition). Remember to think as big as possible

3) Narrow down to each bucket and generate as much ideas as possible (e.g. scope: vertical growth, horizontal growth, new products. Value proposition: additional services, improved quality, etc.)

4) Present the structure (buckets) and then your ideas

Creativity is in direct correlation with you business judgment. Business judjement is directly related to industry knowledge. Focus on the most common industries in the following priority (sorted by probability of geting a case): 1-retail and CPG; 2-airlines; 3-Telecom; 4-banking; 5-natural resources; 6-tech

There are several sources of info to develop industry knowledge:

1) Cases - you simply solve 50-70 cases and get a broad knowledge of different industries, common pitfalls and questions. The key here - find good partners who already had case interviews with MBB companies

2) Company reports, equity reports, IB roadshow docs - usually have a good overview of company and industries. Annual company reports are probably the bast source of information about the industry

3) HBS cases - quite useful, but not sure if lot's of them available publically. Probably worth buying

4) Books - one good book about airlines with numbers and industry analysis can give you all needed industry knowledge

5) News, Industry blogs

For each industry, you should understand:

  • Revenue streams
  • Cost structure
  • Margins
  • Key performance indicators
  • Key revenue drivers
  • Industry trends

Also some comments about particular industries:

1) Retail - make sure you understand key retail metrics (P&L lines, same store sales, revenue per square meter and per person, etc) and how distribution works as well as its metrics (share on shelf, etc)

2) Airlines - read about profitability issues, different routing models, cost structure, industry metric s like load factor and make sure you know all possible additional revenue streams

3) Telecom - I would read industry reports and try to understanf how telecom is transforming with internet penetration and tech innovations

4) Banking - you should know the key products in corporate and retail banking and how they earn money (Interest, commision, transactional)

5) PE / M&A - go through available case examples and read about different PE strategies

Good luck!

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Originally answered question:

How to brainstorm in organized way

Anonymous replied on Mar 11, 2016

I would say you first start by listing of the CATEGORIES or GROUPS for the exercise - then lost out specific examples. For instance, brainstorm list of capital cities in the world. You can just name then from memory... OR show structured thinking by listing out all the continents first, then start with one continent, then last cities in that and then move on to next continent.

Hope that helps.

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Originally answered question:

How to brainstorm in organized way

Anonymous E replied on Mar 10, 2016

I would say that it's important to be structured, even though the question is 'creative'. There are two possible situations after the interviewer asks this question: 1. You are allowed a minute to write down some thoughts: Write down some ideas that come into mind and try to group those ideas in a logical structure. That way the process for you was still free-format brainstorming, but you present it in a structured way. 2. You have to do it straight away with no time to think for yourself: I would use a similar approach, only now the brainstorming is really out loud. Name your idea, write it down and go to the next. Try to come up with groups as you go, and if you see that all of your ideas are falling in the same group/category, take a few seconds to see whether there's another category.

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Originally answered question:

Weak Creative Brainstorming part

replied on Apr 06, 2018

Hey anonymous,

If it's McKinsey, an easy tip is for you to ask for additional time to think about the problem and brainstorm on your own, which is easier than out loud.

Overall, two ways to improve in creativity questions are:

  • think through a pre-existing framework/approach (e.g., value chain, customer journey, production process, etc)
  • get familiar with additional business materials and cases, so that you can further cultivate your business knowledge and acumen (especially important if you come from a non-business background)



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Originally answered question:

Weak Creative Brainstorming part

Anonymous D updated the answer on Apr 06, 2018

Adding on to this . Has anyone worked on this specifically and prepared like a doc of key points from all the common industries and would be willing to share it?

Many Thanks


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Ignacio gave the best answer


MIT MBA | Bain & Co | Ex-Google | 4+ year coaching experience
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