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BCG Case Interview Brain Storming

BCG BCG Case Interview Case Interview
Edited on Sep 05, 2021
3 Answers
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daria asked on Sep 19, 2017

Dear All,

I understand BCG cases are quite open and candidate led. My plan here is to initially ask a few clarifying questions. My aim here is not to get into anything too deep but just to clarify surface level issues (e.g. definitions, clarifying product, really just clarify anything that can be ambiguous or have multiple definitions e.g. what does improve performance mean). In this initial minute or two I also to get a laser focused clarification of the client's objective. Once this is done I then I want to create a structure up front by identfying 3 or 4 buckets (ideally MECE). I will then go through each bucket asking questions and engaging with the interviewer such that I get all the qualitative and quantitive data I need within each bucket. Ideally from here I can form an opinion backed up with evidence, address some risk points and also raise some future steps.

Does this sound like a good approach tweaked for the nature of each case?

Also, I understand BCG can often get to a point where they keep asking for ideas akin to a brainstorming session. If I have an interview that gets to this, should I identify my MECE buckets first and brainstorm within the buckets or can this be more free form?

Many thanks



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Content Creator
replied on Sep 20, 2017
#1 Coach for Sessions (4.500+) | 1.500+ 5-Star Reviews | Proven Success (➡ | Ex BCG | 10Y+ Coaching

Hi Daria,

the approach you have definied is good. As for how to deal with a brainstorming question, you should always identify MECE buckets first, and then brainstorm. In particular, quoting a previous post I wrote, the process could be the following:

  1. Recap all the information received until 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 of your brainstorming.
  3. After having defined the key pillars, 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.

Hope this helps,


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replied on Sep 20, 2017
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School


Sounds like a good approach. Some additions to the key questions you've highlighted:

1) Clarifying questions:

  1. Clarify the business model (i.e. how the business works and what are the revenue streams / core products or business lines)
  2. Clarify the objective both in money terms and timeline (e.g. Our objective is to increase profits by 5M in 5 years). When you have a to select from several options in a case - clarify the selection criteria
  3. Clarify other possible limitations if you feel that it's necessary

2) Questions on creativity

  1. Ask an interview for a minute to think
  2. Think of several buckets of ideas (e.g. organic growth / non-organic growth / differentiation). Remember to think as big as possible
  3. Narrow down to each bucket and generate as many ideas as possible
  4. Present the structure (buckets) and then your ideas

Creativity is in direct correlation with you business judgement that can be trained by solving more various cases with partner / studying various frameworks / reading industry reports / reading HBS cases

Good luck!

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Content Creator
updated an answer on Sep 05, 2021
Former BCG | Case author for efellows book | Experience in 6 consultancies (Stern Stewart, Capgemini, KPMG, VW Con., Hor


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Francesco gave the best answer


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