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Case interview questions
Case interviews at management consulting firms are among the most difficult job interviews, but they are also quite predictable. Once you know the types of questions they ask, preparation is straightforward.
Using years of experience at McKinsey, as well as field reports from thousands of candidates, I’ve crafted a list of 8 common case interview questions, and in this article, I’ll show you how to answer each of them.
Case interview questions – Overview
Types of case interview questions
Most questions in case interviews belong to one of these 9 types:
1. Framework/issue tree questions
2. Market-sizing and guesstimate questions
3. Valuation questions
4. Brain teaser questions
5. Chart insight questions
6. Value proposition questions
7. Information questions
8. Math problems
9. Solution-finding questions
In this article, we’ll discuss how to answer each question, along with the necessary tips and tricks.
How to answer case interview questions
There are the four basic steps to answer case interview questions:
This general outline may vary depending on each type and each question – for example, brain teasers or information questions need only the last step, while market-sizing and framework questions need all four steps to deliver the perfect answer.
Type 1 – Framework/Issue tree questions
If the interviewer asks you to identify factors contributing to a problem or to break down an entity (such as the revenue of a business), he/she is telling you to draw an issue tree.
And to draw a spot-on issue tree, you need to master consulting problem-solving foundations, the MECE principle, and common consulting frameworks. You should check out our other articles on these topics before moving on, because mastering the issue tree is the key to acing every possible case interview.
You also need good business intuition to draw good issue trees, so that’s all the more reason to start reading every day.
Which factors would you consider when tackling this turnover problem?
Job: Factors from the job itself. Further divided into 3 sub-branches
Company: Factors from the work environment within the restaurant chain, surrounding the affected jobs. Further divided into 2 sub-branches
Competitors: Factors from outside the restaurant chain, related to competing job offers. Further divided into 2 sub-branches.
For detailed guides on issue trees, frameworks and their principles, see the articles on Issue Trees, Case Interview Frameworks, and MECE Principle
Type 2 – Market-sizing & guesstimate
These questions go along the lines of “How many trees are there in Central Park?” or “What’s the market size of pick-up trucks in the USA?”
The key to nailing market-sizing and guesstimate questions lies in not the closest results, but the most logical and structured approaches. In fact, the interviewer expects you to follow these four steps:
Unless you come up with something about 10 times the reasonable estimate, don’t worry about being “wrong” – the interviewer is unlikely to have a “correct” number in mind, he/she just wants to see your structured mindset.
This question type is so common, we devote a whole article to it, and our Case Interview End-to-End Secrets Program have a separate package on these questions. Check out our comprehensive guide on Market-Sizing & Guesstimate Questions for more details!
Now, here’s a quick example for you to try and get used to this type:
Market-Sizing & Guesstimate Questions
How to Estimate Logically and Structurally
Break down the problem:
The global smartphone market can be divided into three segments – developed countries, developing countries, and undeveloped countries.
In each segment, the annual unit sales of smartphones depend on four variables:
Solve each piece:
Annual unit sales
=> Estimated global smartphone market: 1.53 billion units per year
=> Actual 2019 global smartphone sales: 1.37 billion units (error margin: 11.7%)
This market-sizing question is solved using a four-step process, which is explained in this article: Market-Sizing & Guesstimate Questions
Type 3 – Valuation questions
Valuation questions are a blend of guesstimation/market-sizing, math, and business. They also require basic finance knowledge.
There are three ways to estimate the value of a business:
In real case interviews, you have to justify your approach then ask the interviewer to give you the necessary data.
(Supposed the interviewer gives you the following data: his current income from the restaurant is $100,000 per year; two other restaurants in the neighborhood – one with 2 times more customers, and another about 0.75 times, have been sold at $1,800,000 and $1,000,000 respectively)
NPV Method: Cato’s Cabbage Farm value = $100,000 / 10% = $1,000,000
Assume the number of customers for Cato’s Cabbage Farm is 1 “customer unit”, then the two neighborhood restaurants get 2 and 0.75 “customer units”.
Type 4 – Brain teasers
Brain teasers are riddles designed to test unconventional, creative, and logical thinking. A famous example of this is Accenture’s “How do you put a giraffe in a fridge?”.
Although not as popular as before, brain teasers might still appear in consulting interviews; therefore, you should spend some time to prepare.
Most brain teasers can be allocated into these seven types:
•Illusion questions require you to bypass misleading details to spot what’s important.
•Pattern/trend questions require you to identify trends and patterns, then fill in the blanks.
•Draw-explanation questions require you to use stories to explain weird and seemingly impossible situations.
•Wording questions require you to find alternative meanings to words to explain impossible situations.
•Letter-trick questions require you to identify meanings hidden behind the organization, composition, and visual demonstration of letters.
•Market-sizing & guesstimate questions require you to estimate vague, sometimes unverifiable figures; we’ve just covered these in the previous section.
In our Case Interview End-to-End Secrets Program, there are +200 brain teasers to help you prepare for these “unpredictable” questions. You can also read our article about Case Interview Brain Teasers for insights on all of these exciting brain teasers, as well as 30 example questions and answers!
Brain Teaser Questions
Cracking the Most Unpredictable Interview Questions with 30 Examples
Open the fridge, put the giraffe in, then close the fridge.
The question never says how big the fridge or the giraffe is.
For the logic and approach behind each kind of brain teasers, see the article on Brain Teasers.
Type 5 – Chart insight questions
You can’t be a management consultant without mastering the use of charts – the complex, scary-looking real-world charts such as those included in our Case Interview End-to-End Secrets Program.
In management consulting and case interviews, most charts are one (or a combination) of these four basic types:
To read these charts and answer chart-insights questions effectively, you must follow a structured, comprehensive process:
You can find a more detailed guide in the Charts section in our article about Consulting Math.
Trends in chart:
Type 6 – Value proposition questions
No business or consulting candidate can succeed without understanding the customers!
Value-proposition questions are not only about correctly identifying customer preferences, but also about analyzing and delivering the answer in a structured fashion. The former relies heavily on business knowledge and intuition, but the latter can be trained methodically and quickly. Personally, I use a “double issue-tree” – essentially a table with customer segments on one axis and proposed values on the other:
For segmenting customers, you can use the following table. However, don’t over-rely on it, since there may be more relevant and insightful question-specific segmentations.
Segments the market based on the geographical location of customers
Segments the market based on personal characteristics of the customers (e.g: age, income, etc.)
Segments the market based on how customers act
Segments the market based on how customer think
In some cases, clarification is also necessary – both to avoid “answering the wrong question” and to narrow down the range of customers/values you need to cover in the answer.
Clarification: A sedan must be branded “Toyota” to be a Toyota sedan – cars with other Toyota-owned brands such as Lexus or Ranz do not count in this question.
Toyota sedans occupy the entry-level and mid-range price segments, so Toyota customers will be more price-conscious than, for example, Lexus customers.
They are also less likely to lean considerably towards one particular factor, so achieving a balance is extremely important.
Type 7 – Information questions
“Information questions” essentially ask if the piece of data you use is obtainable in the first place. In real consulting work, data is not always available – client team members may refuse to cooperate or there’s simply no data on the subject.
There are many kinds of information sources in case interviews/consulting works, but I’ll divide them into primary and secondary sources. Primary sources means you must do the research yourself (or pay someone else to do it for you), such as customer surveys or mystery shoppings. If someone already did that research, and you use their results, it’s called a secondary source – you can get these from the client, the consulting firm you work for, or third-parties such as market research firms or external industry experts.
You can find out more about these sources and how to cite them in real case interviews through this free Prospective Candidate Starter Pack, which contains a glossary of data sources in consulting.
Our Prospective Candidate Starter Pack has a sheet containing all the possible sources of information in case interviews and consulting projects, among numerous other free resources; you can download and use it to answer these questions, by subscribing to our newsletter at the end of this article.
Primary sources: customer survey, customer interviews,
Secondary sources: industry reports, client sales reports, third-party expert interview, client expert interview
Type 8 – Math problems
When you have to do the math, perform back-of-the-envelope calculations in a structured fashion, and say out loud what you’re writing. For one thing, it’s safe; for another, you show that you’re careful, organized, and reliable – just like actual consultants.
We have a Math Practice Tool right here! Use it every day, and you’ll be a master of mental calculations in no time flat!
We have a dedicated article on Consulting Math, which you should definitely read.
End-to-End Secrets Program
Get your end-to-end training to master each question types, “consultant-like” case delivery method and thorough consulting math practice.
Type 9 – Solution-finding questions
When dealing with solution questions, keep these four points in mind:
Last but not least, deliver at least two solutions, preferably three to five. Otherwise, you’ll appear uncreative and lazy to the interviewer’s eyes.
Nailing these questions relies on having excellent business intuition; our Case Interview End-to-End Program has a dedicated Business Intuition package, but you should also train a habit of reading consulting and business articles daily, to sharpen your business mind.
The solutions for the restaurant’s parking space problem can be divided into two types:
Reminders on case interview questions
The questions are not clear-cut in candidate-led cases
There are two extremes in consulting case interview format: interviewer-led (McKinsey) and candidate-led (BCG, Bain).
This list, therefore, is much more relevant to the interviewer-led format; nonetheless, this guide is still quite beneficial for candidate-led cases, because when solving that big problem, you’ll have to tackle small issues similar to the 8 aforementioned question types.
Mastering the fundamentals is crucial to consistent performance
Although it’s good to study the case interview questions, it is no substitute for mastering the fundamental principles.
Learning the exercises without the basics is like building a house without a foundation. My poor neighbor’s house developed a huge crack right down the center because of its weak foundation, so make sure to build your case interview prep a strong one by knowing the basics first.
Once you’ve mastered the fundamentals, you’ll become much more flexible – this quality is getting increasingly important because case interviews are getting less predictable, and more realistic.
If you haven’t, I advise you to read these articles (especially the first 4) before practicing the question types:
Expect the unexpected
If you study those nine question types, rest assured that you’ve covered the majority of questions in case interviews.
However, these are not all the possible questions you might be given. In actual cases, there are always questions that cannot be categorized neatly. If you do not prepare for these questions, it’s easy to be thrown off-balance.
So, how do you prepare for “the unexpected”?
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