Introducing the case interview
Case interviews are at the heart of the selection process at top consulting firms like McKinsey, BCG, Bain, and other selective employers. In practice, they test whether candidates have the analytical horsepower to solve strategic problems. Candidates often find case interviews to be challenging and intimidating. They require a high level of skill and preparation to structure, calculate, synthesize, and conclude. To help support candidates in preparing for and succeeding in case interviews, we’ve compiled the best free resources available on what a case interview looks like, how to succeed in these types of interviews, and how to prepare appropriately. CaseCoach is the world’s leading case interview prep platform. More than 50,000 candidates use CaseCoach every year to improve their dream job chances.Key Takeaways
- Case Study Interviews usually are delivered one-on-one and typically include the sharing of a brief by the interviewer, clarification and reflection by the candidate, closely followed by analysis and synthesis.
- Case interviews are used by management consulting firms and in other sectors, including tech, financial services, or non-profits, particularly for the recruitment of employees involved in shaping strategic initiatives.
- Case interviews assess candidates’ problem-solving skills, presence, and communication. Problem-solving skills include structuring, numeracy, judgment and insights, creativity, and synthesis.
- A good case structure will pass the AIM test i.e., it is Answer-focused, Insightful, and MECE (Mutually Exclusive and Completely Exhaustive).
- Candidates can ace case math by following a four-step process, and by keeping workings tidy and simple, working with the interviewer, and preparing for the kind of math they’ll face.
- Displaying strong judgment, leading the case reliably and confidently, and delivering an impressive case conclusion will also set candidates apart.
- Some firms use written cases as well as estimation and market sizing questions to assess candidates. These require specific preparation.
- Successful case interview candidates typically practice cases with other candidates, learn the theory, practice key skills, and receive coaching.
- CaseCoach has numerous resources to help you succeed in your interviews including a comprehensive Interview Prep Course, Case Math Course, Coaching services from former interviewers, as well as drills to help you build the necessary muscles for case interview success.
Case interview format
Case Study Interviews usually are delivered one-on-one, last around 30 minutes, and follow five steps. They are:
Brief: The interviewer gives a brief for the case. They explain the context the organization in the case is operating in and the challenges that they’re facing.
Clarification: The candidate then has a chance to ask clarifying questions, perhaps to test or confirm an understanding of the context or of the problem itself.
Reflection: The candidate takes around 30 seconds to reflect and lay out a structured approach to solving the case.
Analysis: The interviewer and the candidate work through the case together, carrying out analyses and ultimately driving towards a recommendation. This is the part of the case where the candidate will be handling numerical questions, reviewing exhibits, and coming up with creative ideas. It comprises the majority of the time spent on the case.
Synthesis: The candidate synthesizes their findings and makes an overall recommendation.
Where and why case interviews are used
From the client’s brief, through the analyses, to the recommendation, case interviews simulate the job itself. MBB firms (McKinsey, BCG, Bain) use the case interview as it’s a statistically proven predictor of how well a candidate will do on the job. Top consulting firms, however, did not invent the case interview. They only adapted it from the Case Study Teaching Method concept, developed at Harvard Law School in the late 19th century. When they were created, top management consultancies mirrored their organizations on law firms, creating many parallels between law and consulting. Today, case interviews are also used by employers outside of management consulting, including in tech, financial services, or non-profits, particularly for the recruitment of employees involved in shaping strategic initiatives. The following employers are known to use case interviewing:What case interviews look like in practice
Case interview video examples
In the videos below, former McKinsey interviewers and consultants demonstrate an actual case interview using an investment case named FlashFash and a case on the Canadian Wildlife Federation. It includes helpful feedback on how the candidate is doing during the case.FlashFash
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Canadian Wildlife Federation
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Candidate-led vs Interviewer-led cases
Although consulting case study interviews have a set format, they can be delivered differently. Some can be candidate-led, and others can be interviewer-led:
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Initial round vs final round
Most top consulting firms use at least two rounds of interviews before making a final hiring decision. You can expect to go through 2-3 full interviews in each round, including both a case and fit interview. That said, there are some regional and firm variations. While some firms may have three interviews in the final round, some may only have two, and others may have a full fit interview as one of the interviews. Make sure to confirm the types of interviews you can expect when applying to your local office. Here are some of the key differences between the final and first-round interviews at top consulting firms.The bar is higher
The good news is that making it into the final rounds means your odds of receiving an offer are ~50% and therefore higher than the ~25% chance of passing the first-round interview. However, the caliber of the candidates is much higher in the final round and there are much fewer candidates. As such, despite its similarities with the first round of interviews, the final round can be fraught with surprises.The interviewers are different
Although the interview format is the same, a major difference is the seniority of the interviewers. In your first round, you can expect to be interviewed by MBA or manager-level consultants. In the final round, your interviewers will be more senior and include at least one Partner.The decision is different
For a first-round interview, the interviewers are simply asking the question: is putting you in front of a few Partners for another 2-3 hours going to be worth their time? In the final round, the decision is a much bigger one, because the interviewers are deciding whether to extend a job offer. The firms are likely to be more lenient in the first round where they may allow for slip-ups in some elements of the interview if they see potential in other elements. The interviewers will then provide feedback to see whether you can manage to implement it and improve in the final round of interviews. They are much less likely to take a risk on an imperfect candidate in a final round. For a final round to go successfully the interviewers need to be more than convinced one way or another and are less likely to give the benefit of the doubt.Expect the unexpected
As you’ll be meeting Partners in the final round of interviews you can never be too sure of what’s going to happen. While the first-round case interviews may often seem more off-the-shelf and scripted, the final round cases are handled by Partners who are less likely to use off-the-shelf material or to abide by a set format. Partners are also more likely to use cases based on one of their own projects and are more likely to take the candidate-led approach. Making an offer is a big decision for the Partners, so they will want to get it right. If they’re unsure in any way you’re unlikely to be extended an offer. To give yourself the best chance of success we highly recommend putting the time and effort into learning how to nail consulting interviews by using the best resources available and investing in coaching to identify your weaknesses and polish your case skills.The most common case study interview questions
Case study interview questions generally mirror the work of the employer. If a candidate is interviewing for a role that is focused on a specific industry or function, it’s necessary to have researched the typical projects that might be worked on and their respective solutions. These types of problems will likely come up during the case interview. If a candidate is interviewing for a generalist role, they should get familiar with the most common business questions faced by CEOs, and their approaches to solving them. Consultants at top consulting firms are commonly involved in solving these questions and they often tend to come up in business case interviews. The questions include:Improving Profit
“A fast-food restaurant has had declining profits over the last three years. What is the cause and how can the situation be turned around?”Growing a business
“The CEO of a cycle hire company based in Amsterdam is looking for growth opportunities. What are some ways they can go about doing this?”Reducing Costs
“The Finance Director of a motorbike manufacturer has been asked to find 10% savings within the next two years. What approach do you suggest they take to find and realize savings of this size?”Entering a new market
“A mobile technology firm sees South America as their next growth opportunity but doesn’t know which geographies or products to focus on growing in this region. How would you advise them?”Launching a new product
“A successful skincare brand based in the USA which serves women over 50 wants to launch a new range to men over 50 and is looking for guidance on how to launch the product successfully”.Pricing a product
“A biotech firm based in Washington has developed a cutting-edge formula to reduce the impact of city pollution on human skin. They are looking for support on deciding what price to place the new product at.”Acquiring a new product
“A global insurance company has purchased a niche insurance firm in Thailand and wants to know how best to maximize the profit and operational synergies available from the acquisition.”Deciding a new investment
“A pottery manufacturer in rural England is considering purchasing a new piece of machinery that will paint the pottery without the need of a human. Should they make the investment and no longer offer hand-painted pottery?”Responding to a competitive threat
“The dawn of agile project management has put a traditional provider of project management training at threat and their revenue has been declining over the last few years. What can the firm do to revive its leading place in the market?”Optimizing a process
“A popular coffee shop chain is struggling to keep up with demand and queues out the door during the morning coffee run are commonplace. How can the chain improve its throughput of coffee sold at peak times?” To avoid candidates gaming the system, the top-tier firms are moving away from the more common types of cases. London Business School MBA students reported that a third of the case study interview questions they saw when interviewing with top consulting firms did not fall within any of the above question types.Which skills case study interviews assess
While the primary purpose is to assess candidates’ problem-solving skills, case study interviews also provide a read on whether candidates have the presence and communication abilities necessary to give a positive and professional impression. Interviewers use scorecards that track key problem-solving dimensions to assess a candidate’s performance in these areas. Some of these can be seen in the graphic below.
Additionally, if a candidate is interviewing for a role focused on a specific industry or function, their expertise in that area might be assessed as part of the case.
Ace the case with the right structure
What a good structure looks like
Structuring is among the most difficult parts of the consulting case interview. While there isn’t just one correct structure for a case interview question, there are many wrong ones. A good structure needs to focus on the right question, break it down into an exhaustive set of independent drivers, provide an approach to solving the case, and supply helpful insights. A common approach to ensuring a good structure is the AIM test (Answer-focused, Insightful, and MECE). To expand upon this:
- Answer-focused: This means two things in practice: the structure focuses on the right question, and it provides an approach to answering that question.
- Insightful: This means the structure is tailored to the specifics of the client or problem in the case and that it is not generic. If the structure can be applied to another case of a similar type, then it hasn’t passed the Insightful test.
- MECE: Being MECE means that the drivers outlined in your structure are Mutually Exclusive and Collectively Exhaustive, which essentially provides an approach that will solve the case. ‘MECE’ is a well-known acronym among consultants.
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Given how critical solid structuring skills are to case interviews, CaseCoach has many materials and practice rooms to develop and refine your structuring muscle. Our Interview Prep Course contains 7 lectures dedicated to helping you master the art of structuring.
You can refine your structuring abilities with our structuring drills which also provide multiple solutions to demonstrate what great structuring looks like. Finally, our case library (part of the Interview Prep Course) containing 100+ cases each provides opportunities for you to further test and refine your structuring in a realistic case interview context.
Using frameworks to structure consulting cases
Thirty years ago, people started to use frameworks to structure cases, as was popularized by the book “Case in Point”. Another book, “Case Interview Secret”, went further by suggesting that most consulting cases could be solved using a single “one-size-fits-all” framework. Unfortunately, candidates who depend on these books today are being led down the wrong path. Top consulting firms are increasingly using unusual case questions that do not simply fit neatly into a generic framework. A candidate needs to demonstrate to an interviewer that they are capable of strongly structuring a case, as opposed to just relying on a framework. Although frameworks should not be memorized and applied as is, knowing them can be a good starting point and source of inspiration when crafting bespoke consulting case study structures. Here are the five most popular frameworks candidates should know:1. Profitability Equation
This is the mother of all case interview frameworks as there’s a high chance that some form of a profit problem will come up during multiple rounds of consulting interviews. Simply put, it consists of breaking down profits into revenue and cost. Revenue is the quantity sold multiplied by the price of the product and cost is the sum of all the fixed and variable costs. Increasing profit will require moving these drivers in the right direction. CaseCoach offers resources to help you master profitability questions in a case study interview.
2. Porter’s Five Forces
Porter’s Five Forces help assess whether an industry is attractive given the competitive forces at play. It’s a good tool to use when considering whether to enter a new market: The five forces are: A company is unlikely to be profitable if its industry has few potential customers, is dominated by a small number of competitors, has substitutes readily available, experiences many new entrants, or where critical resources are controlled by powerful suppliers.
3. The 4Ps
The 4Ps framework, or “Marketing Mix”, is often used to establish an effective strategy for launching a new product to the market. For a strategy to be effective, the four components of the marketing mix need to be aligned. They are:
4. The 3Cs
Let’s now look at another framework, the 3Cs, that brings supply and demand to the next level. The 3Cs refer to Company, Competitors, and Customers. The term was coined by a Japanese management consultant who later became an academic, and quickly became one of the most-used strategy frameworks. In the 3Cs, demand is renamed as customers, while supply is broken down between the company and its competitors. If a company wants to win in a market, it needs to better satisfy customer needs than its competitors.5. BCG Matrix
The Boston Consulting Group (BCG) Matrix, or growth-share matrix, is a framework that helps businesses prioritize where to focus to maximize their growth and shape their strategy. It classifies businesses into four categories based on the growth of the industry and the relative market share. They are:
Ace the case with stellar math
As with so many other aspects of case interviews, there’s a formula you can use to structure your thoughts and analysis. When you’re confronted with a math problem, it’s recommended that you follow a four-step process, keep workings tidy and simple, work with your interviewer and know what kind of math you’ll face. We will expound on these below.Follow a four-step process
The first step before you begin to solve the problem is to verbally describe your approach. This will not only help structure the question in your mind but will also give your interviewer the opportunity to correct any mistakes or incorrect assumptions you’ve made right off the bat. In a best-case scenario, the interviewer might even ‘sign off’ on your approach, either verbally or nonverbally, by indicating that they agree with how you’ve decided to tackle the problem. The second step is to work through the calculations, making sure to write everything down and describe what you’re doing verbally to the interviewer, so that they can follow along more easily. The third step is what is called a ‘sanity’ or ‘sense’ check. After you’ve completed your calculations, take a breath and try to adopt a bird’s-eye view of the problem. Does your solution make sense? For example, if you’re trying to assess the yearly revenue of a well-established multinational law firm and your final result is just a few thousand dollars, common sense should tell you that you need to return to your calculations and find the error. Finally, step four is interpretation and presentation: you need to demonstrate to the interviewer that you can glean meaningful (and hopefully practical) insights because of your calculations. Ask yourself whether your solution is realistically achievable and whether it supports your initial hypothesis.Keep workings tidy and simple
Throughout this entire process, you must ensure to write things down and to make sure that your calculations are tidy and simple. Many candidates have been tripped up by an untidy workspace which can confuse the candidate and give off a bad impression to the interviewer, who will be expecting a professional and organized approach to the case at hand. Therefore, you’ll want to use a fresh sheet of paper for each problem (and for each non-trivial calculation), write neatly and give yourself ample space on the page to do so, and align your equal signs on the page to make things visually tidier. Pick friendly numbers when you can, compute one operation at a time, and avoid multiplying percentages together (this often leads to errors). Also, try to recognize when to use a table in order to synthesize different units or types of data you’re given. Finally, ask your interviewer if it’s okay to round numbers in order to make things easier — they are often comfortable with this and it demonstrates that you have your eye on the essence of the problem rather than trivial details.Work with your interviewer
On that subject, it’s a good idea to work with your interviewer throughout the case interview. As we mentioned earlier on, try, and get your interviewer to sign off on your approach upfront. State your assumptions and ask them to fill in the gaps in your knowledge of certain data sets. For estimation questions where this might not be appropriate, state your own assumptions so that the interviewer can follow along with your thought process. And as you do your calculations, verbally describe everything you’re doing: many candidates think it’s clever to stay silent and then impress the interviewer with the correct answer after a few minutes of quiet calculation, but the most successful candidates try to draw the interviewer into the process. This allows you to react in real-time to verbal or non-verbal feedback. Not only does this give the interviewer the impression that you are confident and work well in a team, but it also gives them the opportunity to correct any errors.Know and prepare for the kind of math you’ll face in a case
Learn basic operations, key math concepts, and business math
There are three categories of math problems you need to know how to ace math questions in case interviews. They are basic operations, key math concepts, and business math. The basic operations are addition, subtraction, multiplication, and division. You learned these operations at school, and yes, they will be pivotal in case interview math. Once you’ve got the four operations down, you can move on to a few key concepts that usually crop up in case interviews. You’ll most likely have had some experience with some of these concepts, such as fractions, percentages, and simple growth. Beyond these, you must also have a good grasp of compounding, weighted averages, probability, and algebra.Stand out with pro-tips
While mastering the four operations and key math concepts will set you up for success with case interview math, there are several pro-tips that will help you stand out from the crowd with impressive speed and reliability. Pro-Tips include mastering how to keep track of zeros, simplifying your calculations, and memorizing frequently used factions.Keep track of zeros
The number one math mistake that we observe in case interviews is miscounting zeros. Case questions often deal with large numbers, sometimes in the millions or billions. Because of this, it’s easy to misplace or leave out a zero, making your entire calculation inaccurate. You can avoid this using one of three methods of keeping track of zeroes: a) counting zeroes, b) using scientific notation, or c) assigning letter units. All three methods are detailed in our Case Math Course, provided as part of our Interview Prep Course. Try out all three methods and decide which works best for you.Simplify your calculations
Being fast and reliable does not necessarily mean being a human calculator. The secret to being fast and reliable, and impressing your interviewers, is to make life easier for yourself by simplifying calculations. Our Case Math Course contains three lectures addressing ways you can simplify your case math calculations: simplification with distributive properties, simplification with factoring, and simplification with rounding. Learn these concepts and practice case math questions using these for easier and more reliable calculations in your case interviews.Memorize frequently used factions
Some fraction values are used so often in case math that knowing them, their percentage values, and their decimal conversions can save you significant time. First, remember that divisions can be represented either as fractions, decimals, or percentages. For example, the fraction 50/100 = 0.5 = 50%. A good rule of thumb is to memorize the fraction and corresponding decimal and percentage values of 1/2, 1/3 all the way through to 1/10.Invest in your preparation
While you may think it’s a waste of time to brush up on your math skills, you’re probably a little out of practice when it comes to doing calculations by hand after years of Excel and calculators. Plus, remember that you’ll be doing these calculations with a pen and paper in a highly pressurized and time-sensitive environment. So take the time to go over all the concepts earlier mentioned in the article. Our Case Math Course, provided as part of our Interview Prep Course, covers all you need to ace case interview math. It includes comprehensive but concise video lectures on the four operations, key math concepts, CaseCoach’s pro tips, and business math. Dig in whether you want to refresh your math skills, fill any skills gap, or bring your speed and accuracy to the next level. Once you’ve familiarized yourself with the concepts, it’s time to practice, practice, practice. You can, of course, practice doing these calculations by yourself, but we strongly recommend that you do so in the context of a practice case question. Our Calculation drills (included in our Interview Prep Course) offer timed question sets across various topics that can help you boost your calculation speed and accuracy. For case math questions typically accompanying charts and exhibits, try out our Chart Drills (also included in our Interview Prep Course) to learn how to stand out in your case interviews.Other skills to ace the case
Ace the case with stellar judgment & insights
Judgment and insights involve connecting findings to develop sound recommendations, make reasonable hypotheses, share impressive insights, and flag far-reaching and non-obvious implications. In practical terms, during a case, it means drawing conclusions from a chart, a table, or a new piece of information. This is a key, but often overlooked, dimension in the assessment process. Showing a good capability in this can be a major way to differentiate yourself as a candidate. You’ll often be given exhibits in cases. You’ll be asked open-ended questions about them and you’ll have to generate qualitative insights and reach judgments from the material. There are a variety of exhibits that might be encountered during a case interview and that can be a lot of data to handle in a short time. However, there’s a fairly set process you can follow when you’re dealing with them, explained below: First, examine the exhibit and state what the data describes at a high level. In other words, say what you see. This buys you a bit of time and helps you get familiar with the detail that is in front of you. As you’re doing this, you should begin to think about any data points that are relevant to the question. Secondly, you will want to point out these insights and ideas to the interviewer. In this phase, it is important to keep your eyes on the ball and focus your observations on what is relevant to the question asked and the overall goal of the client. Otherwise, you will quickly get overwhelmed with observations and struggle to make sense of it at all. Some of your observations will be simple. Beyond simple observations, though, you typically need to look for ways to combine numbers and draw more advanced comparisons to make a point. Look for ways you can tease insights out of the combination of some of the rows here, or basic calculations that you can do between columns. Finally, once you’ve laid out a number of insights like this, you want to close by summarizing your overall findings and what they mean for the problem you’re tackling. CaseCoach’s chart drills are included in the Interview Prep Course and they provide charts and tables in the numerous formats used in case interviews to help you build your judgment and insights muscle.Ace the case with proactive case leadership
Being able to lead the case reliably and confidently is one of the few dimensions that candidates can use to distinguish themselves among a high-caliber group of candidates. Case leadership is particularly important for candidate-led cases, where candidates are expected to chart their own path in solving the case. If you’re able to take ownership of the case, drive the conversation, and suggest the next steps every step of the way, your interviewer will immediately see the value you can add to the job. To show your case leadership skills, you need to stay focused on the case question and the client’s objective and you need to show that you can develop an answer early on. Case leadership can seem like an ambiguous dimension at first, but it becomes clear with practice Strong case leadership often involves deploying a “hypothesis-driven” approach. A hypothesis is an educated “guess” at what the solution of the case could be. In a hypothesis-driven approach, the candidate will mention early in the case what potential solutions could be, and include in their structure the analyses to disprove these potential solutions. While the hypothesis-driven approach is a shortcut to reaching a solution, it should not be interpreted as announcing the solution of the case before starting the analyses. Instead, candidates should think about it as testing out some likely solutions. This may sound obvious, but often, candidates will act as passive recipients of an assessment during their interview. Instead, approach the case as a thought partner with your interviewer. This reflects the idea behind a case. If a case is an abbreviated client project, you’re supposed to be acting as a consultant and be proactive, poised, and collaborative. We cover this in much more depth within our Interview Prep Course, but here’s a great mindset hack to help you build your case leadership skills now: play the role of a consultant to your interviewer. To hone your case leadership skills and set yourself up for success, you can also book coaching with one of our former interviewers and consultants for top consulting firms on CaseCoach.Ace the case with an impressive conclusion
Synthesis is a key skill assessed by the case interview, and it’s predominantly assessed at the end of the interview. You must tick the box for each skill being assessed, so delivering a strong conclusion to the case question is important if you want to succeed in the interview. Beyond that, it’s the final impression you’ll leave your interviewer with at the end of the case, so it’s an opportunity to finish on a high note. Unfortunately, many candidates miss the opportunity to show their synthesis and communication skills because they don’t know what a great conclusion looks like. It’s too easy to waffle and lack concision in your recommendation, and it’s also tempting to get the case over with by offering a half-baked conclusion. Your job here is to provide a clear and sound recommendation that convincingly answers the overall question and to describe the key supporting points that informed said recommendation, as well as any next steps.How to structure your case conclusion
As with most parts of the case interview, there isn’t a single right way to carry out a synthesis, but there is a framework that we’ve found helpful. The framework has four steps.- Quickly playback the case question to the interviewer.
- Answer the question directly and briefly by distilling your response into a single sentence if you can. This means you’re presenting the answer first, rather than explaining your points and then presenting the answer.
- List supporting points that back up that conclusion. You’ll typically have between two and four key supporting points here, corresponding to the findings of each of the analyses you conducted during the case interview. They should be crisp and concise. They should feel more like bullet points than paragraphs. You can also enumerate them.
- Conclude with the next steps, which could either be practical next steps to implement your recommendations or further research to clarify what’s missing or to confirm your recommendation.
Video example of an impressive case conclusion
A former McKinsey consultant demonstrates below a framework for effectively concluding a case using an investment case named FlashFash:▶
Learn how to effectively synthesize and conclude cases with our Interview Prep Course.
Alternative case formats
Some firms adopt other interview formats beyond the typical case interview to assess certain qualities. Amongst the two most popular are written case studies or estimation cases and Estimation and market sizing questions. Here’s how to approach them:Written cases
The goal of a written case is to simulate actual consulting work even more closely than in a traditional case interview. Like a classic case interview, the candidate is asked to make a recommendation about a specific business problem. The candidate is given a series of paper documents, sometimes up to 50 pages, which include the client context, interview insights, press articles, market or company data, and so on. Some of the documents are usually not useful for the resolution of the case — so expect some red herrings! You will have to structure the problem, run some numbers and generate some ideas – just like in a live case interview. Ultimately, your responses will be delivered in the form of a short presentation. The presentation is shared and discussed with the interviewer, who will play the role of the manager or the client. Candidates are evaluated on both the content of the presentation and on its form. On the content, the evaluation criteria remain similar to classical case studies. On the form, the quality of your slides and of your oral presentations will be assessed. Although you may have more time in a written case than a live case, the test is generally more difficult to pass. Candidates often fail due to seemingly basic reasons, such as not answering the questions directly, having inadequate slide presentations, or errors in the quantitative analysis. To do well in a written case, we recommend focusing on getting the following right:Organize your time
Start writing the first slides during the first half of the allocated time. Begin by reading the questions you need to answer, then quickly browse the documents provided and read the ones that contain the information you need to answer the questions. Mark the pages that will be useful for each question, then put the other documents aside. This will save you time because, as we mentioned, there will certainly be more information than necessary. We recommend starting with the quantitative question because it often structures the final answer. The more creative questions should be faster to solve and can be answered last.Start with the answer
A common mistake in a written case is focusing too much on the analyses where one ends up omitting the overarching client questions. To avoid this, start your presentation with an executive summary by repeating the client questions, giving a direct answer, and listing the key supporting points. From there, add a slide for each key analysis and wrap up with a conclusion slide with next steps.Design professional slides
Slides must have straight lines, aligned objects, neat handwriting, etc. They should contain only essential information. Remember this is a presentation, not prose. Each slide must have a short title, carrying a message summarizing the slide. The titles of each slide put end-to-end must tell the story you want to communicate.Substantiate qualitative conclusions
Use numerical data as much as possible and do not make any statements without being supported by well-defined facts or assumptions — which you can footnote. Overall, a written case will involve the same problem-solving dimensions as a case interview. You’ll be asked to structure the problem, run some numbers, analyze data, generate ideas, and synthesize your findings. Therefore, to succeed in this kind of assessment you still need to know how to be successful in a standard case interview. The CaseCoach Interview Prep Course contains downloadable examples of written cases to help you prepare for and succeed in written case interviews.Estimation and market sizing questions
Estimation and market sizing questions are often presented within a wider case, but they can sometimes feel like mini standalone case questions themselves. They include questions such as: “What is the estimated monthly revenue of a sandwich shop near inner-city offices” or “What is the estimated number of SUV cars sold per year in North America?” Here’s how to approach them.Clarify the problem
The first thing to do is to fully clarify the question and scope of the answer. You don’t want to start sizing the wrong market. Make sure to clarify important parameters such as whether the answer needs to be in units or currency, what the relevant time frame is, and what type of product is in question (e.g., only new cars, or new and used). Don’t dive into estimating the market without defining the parameters first!Decide on which of the two approaches to use
Market sizing questions can be solved in two ways: top-down or bottom-up. The top-down approach involves starting with large macro numbers and working down. You might begin with the population of the relevant country, break out some segments based on age, estimate the propensity of each age group to buy the item you’re sizing the market of, and then make assumptions about how frequently these people make purchases. The other approach is bottom-up where you start with small numbers and work your work back up. Begin by considering how many vendors there are in any given locality and the sales that we assume go through each vendor, then scale that up to the population at large. For example, if you’re estimating the number of takeaway coffees purchased per day in the UK, you may estimate the number of coffees bought per coffee shop, then the number of coffee shops per town, multiplied by the number of towns in the country. Sometimes you’ll have a personal preference for using top-down or bottom-up approaches and usually either can work. Make sure to lay out your approach and share it with your interviewer before performing the calculations. This will give the opportunity to decide upon the best method and will reduce the risk of getting lost in the numbers.Use segmentation
By generalizing the market too much, you’re likely to estimate a market size that’s way outside the ballpark. Instead, by segmenting the market into 3-4 segments, you can get to a more accurate number and show your ability to simplify—but not over-simplify—a complex market. For example, if you’re estimating the number of takeaway coffees purchased in London every week, you might consider the population of London and bucket them into three different types of coffee buyers: those who love a daily coffee, those who buy coffee 2-3 times a week, and those who prefer to make it at home. By segmenting the market, you’re able to account for different buying behavior and to avoid overgeneralization.Make the right assumptions
In any given market sizing question, you’ll need to make assumptions to calculate figures, such as population sizes, the number of households, and the average number of children per family. You’ll typically get some information specific to the case from your interviewer, but beyond this, you need to make assumptions and apply your own judgment. If your assumptions are too far off, you’re unlikely to reach a sensible answer and may even look a bit silly in front of the interviewer. There are some key facts you’re definitely going to want to know, such as populations of key countries, average life expectancy, the average number of people per household, median income, GDP growth rate, inflation rate, and the base interest rate. Rounding these figures is perfectly fine. Just make sure they’re in the ballpark of logic and sense!Sanity check your answer
When you reach an answer, make sure to check it makes sense and that it’s not too large or too small. Do this by comparing the figure to other figures you know. For example, is it reasonable that 50 million coffees are purchased every day in London if there are only 10 million people in the city? If your answer doesn’t look right, you may have made a miscalculation or a wrong assumption, so review your approach to remove mistakes. The CaseCoach Interview Prep Course contains 12 downloadable examples of written cases to help you prepare for and succeed in written case interviews.How to prepare for the case interview
Case study interviews are no easy ride, but candidates can give themselves the best chance of success by dedicating time to prepare for case interviews. It is generally accepted that it takes 60+ hours of preparation to truly master consulting case interviews. Here’s how successful candidates spend this time:1. They practice cases
While it might be cliched, ‘practice makes perfect’ is true concerning consulting case interviews. It takes at least 25 live case interview practices, as both the interviewer and candidate to reach a good level of case proficiency. Playing both roles of the interview is useful in learning best practices from others. To make the most of case study interview prep time, candidates should use:- An interview scorecard, like one used by each MBB, that assesses all the dimensions of the case study interview
- High-quality case interview examples that closely resemble the ones in real interviews, test the right skills, and where top-mark answers are provided
- Good case partners who can deliver a case well and provide useful feedback
