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Here is a comprehensive case interview preparation guide

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Step 1: Learn the Basics

Time required: 1-3 weeks

Get familiar with the basic frameworks to build an inventory of factors and aspects to choose from, when developing an approach to the case. Use MBA casebooks below to self-practice using the frameworks on actual cases, while keeping the frameworks at hand. 

Most useful frameworks:

  • Profitability framework (revenue and cost breakdown) - for cases, where the candidate first needs to diagnose a profitability issue (e.g., drop in profits, stagnating revenue) 

  • Business Situation framework (Customer, Company, Competition and Product) - for deciding on New Product launch or New Market entry, Turnaround (where the cause of the profitability issue is known) 

  • Growth framework (Existing / New Customers, Existing / New Products, M&A and JV opportunities) -  for cases with Revenue growth objective 

  • 4Ps (Product, Place, Price, Promotion) - for go-to-market strategy, when the client has already decided to enter a particular market or launch a new product

  • Transformation framework (Current State, Improvement Levers - e.g., automation, remove duplication of work, just-in-time, Implementation) - for cases of Cost-cutting in operations 

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Step 2: Start Practising

Time required: 2-4 weeks

Find case partners and start doing live cases. If you are still in university, work with your peers, otherwise you can find case partners online - see suggested resources below. At this stage, focus on selecting the right factors rather than tailoring the framework, therefore you can still use printouts. Get familiar with key considerations of common industries. Work on a range of market sizing questions - these are great to practise math and structured top-down communication. At the end of this stage it is worth getting feedback from an experienced interviewer or coach to learn the best practices. 

Key considerations by case section:​

  • Recap the question: restate the prompt in your own words to ensure you haven't missed or incorrectly recorded any key details.

  • Clarifying questions: before setting up your framework, in addition to understanding any unfamiliar terms, clarify objective (usually a financial metric), timeline to achieve the objective, understand the product (unless very clear), and client's business model (who is the customer, and how they are charged). Each of these can help develop a more suitable framework. Avoid asking for data and limit the number of clarifying questions to 4-5. 

  • Develop and communicate your framework: take 1-2 minutes to develop your framework on paper (landscape orientation!) in an issue tree format, and communicate it to the interviewer top-down: buckets first. Rule of thumb is to have 10-12 factors in the bottom of your issue tree. If the framework is very generic, make sure to add some specific examples for 4-5 of the factors. 

  • Lay out a hypothesis: state your initial answer to the case question, along with the data you will need to support it and the bucket you would start from (e.g., "My hypothesis is that the client should launch the product as there is demand for it and not much competition in the space, and they will be able to generate significant profits as a result. In order to prove my hypothesis, I would like first to understand the demand for the product"). Especially important in candidate-led cases, where the candidate needs to choose where to start.

  • Exhibit reading: take 30-60 seconds to learn the chart (including the legend and scales), and ask for clarifying questions if necessary. Identify the insights from the data, starting from the "obvious" and looking out for the unusual - correlations, outliers. State 3-4 insights from the chart, while tying it back to your hypothesis and client's question. Think out loud on what could be the root cause of your findings and what are the implications.

  • Calculations: always start from communicating your approach in words to the interviewer, giving them the option to intervene if you are taking the wrong path or missing important factors. State any assumptions explicitly. Execute calculations fast and accurately (better accurately than fast). Talk through your calculations if you are comfortable doing so (again, better to calculate accurately).

  • Synthesis: once you reach a quantitative answer, it is crucial to state the implications of the answer ("so what"). Synthesis should include at least two aspects: magnitude (is the number large or small), relation to the client's question and hypothesis (what does it mean for the answer). Third, optional aspect of the synthesis, which in many cases differentiates good candidates from great ones, is a quick sensitivity check - did you use any assumption during the calculation that might be too optimistic or too conservative, which if not true, would significantly change the result.

  • Creativity questions: take a minute to develop a "bucketing strategy" for your ideas. Communicate these 3-4 buckets to the interviewer, before listing the ideas. As a rule of thumb, 2 ideas per bucket should be enough. Try to develop at least 1-2 ideas which are physically possible (i.e., don't require time travel), but are "out of the box" and innovative.

  • Recommendation: again, take a minute to gather your thoughts. Start from answering the client's question (ideally the answer would be actionable - e.g., acquire the company), supported by 2-3 facts uncovered during the case (important: do not recommend your ideas from the creativity question, these have no supporting evidence!). Wrap up with 2-3 risks and/or next steps - here you can use your ideas from the creativity question. 

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Step 3: Practice Mental Math

Time required: 1-3 weeks

Fast and accurate calculations won't secure you an offer, but math errors can definitely result in a ding. All consultancies want to hire candidates who are highly analytical and comfortable with numbers.  Unfortunately, most firms don't allow the use of calculators, and for many candidates it's been 5-10 years since high-school, and they have only vague memory of what a long division is. It's time to go back to basics, learn key mental math techniques, and practice until you can calculate what is 25*45 within 10 seconds.  

Key consulting math concepts  techniques to learn and practice:​

  • Financial formulas: get familiar with formulas for basic business concepts, such as Breakeven point: BE = Fixed Cost/[Units*(Price - Variable Cost)] and Return on Investment: ROI = Annual Profit / Investment.

  • Number rounding: it is generally acceptable to round numbers by +/-10%, but confirm with the interviewer (in 90% of the cases, the interviewer won't object).

  • Handling large numbers: revenues and profits will generally be counted in millions and billions. Find a convenient way of handling large number, whether through the use of scientific notation (e.g., 2,000,000 = 2 * 10^6) or shorthand labels (K, M, B)

  • Long Multiplication / Division / Addition / Subtraction: remind yourself the method and learn useful shortcuts, like factoring (e.g., 25*45 = 100/4 * 40 + 100/4 * 5 = 1,000 + 125 = 1,125)

  • Multiples of 10: when multiplying or dividing by a multiple of 10, just add or remove the corresponding number of zeroes (e.g., 250 * 10,000 = 250 + 4 zeroes = 2,500,000) 

  • Working with percentages: learn the conversion table between common fractions and corresponding percentages (e.g., 1/8 = 12.5%, 2/3 = 67%, 3/4 = 75%). A useful shortcut is to multiply percentages first before multiplying by the base (e.g., 180 * 80% * 25% = 180 * 20% = 36)

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Step 4: Ace the Case

Time required: 2-4 weeks

It's ​time to put aside the framework printouts and ramp up the live case practice. Aim to reach a total of 25-30 live cases before the interview. Every 5-10 cases "check-in" with an interview coach or an ex-consultant friend to ensure you are on the right track and polish the delivery of the case. Make sure you tailor your framework for each case, start working on unusual case types (i.e., not profitability or market entry) and learn to read more complex exhibits and charts. By the end of this step, you should be able to crack cases consistently, while doing the math accurately and fast.

Types of cases to practise:

  • Market sizing: the most basic type of cases (e.g., how many pizzerias are in New York City?), usually solved from either the demand or the supply side, top-down or bottom-up (e.g., number of pizzerias = demand for pizza / supply of one pizzeria)

  • Profitability: generally requires investigation of an issue causing a profitability decline, using a breakdown of revenues (e.g., by price * volume, product mix, geography, distribution channel) and costs (e.g., by fixed and variable)

  • New Business: the client is looking to launch a new product or enter a new market. Requires a comprehensive view of the market. Typically understanding 3C+P: Customer, Company, Competition and Product would offer the required insights (e.g., large market with fragmented competition base would support market entry)

  • Go to Market: the client has decided to launch the product and is asking for go-to-market strategy. Typically the 4P framework: Product, Price, Place, Promotion would help to discuss the key aspects of the go-to-market strategy.

  • Operational issues: the client is facing an issue with a certain part of operations (e.g., how can we reduce queues). Breakdown the process to steps, and identify levers to improve each of the steps.

  • Cost cutting / Transformation: the client is looking to reduce a particular cost item (e.g., labour cost). Typical approach includes establishing the current state (e.g., understand the structure of the team and allocation of effort by process), identifying improvement levers (e.g., automation, waste reduction) and implementation (e.g., sequencing of the process improvement, communication).

  • Growth: the client is looking to grow revenues. Develop ideas across the organic growth matrix (Existing / New Customers, Existing / New Products) and inorganic levers (M&A, JVs).

  • M&A: the client is looking to acquire another company in either a vertical (customer or supplier) or horizontal (competitor) move. Beyond the regular financial considerations, evaluate synergies (on the cost or revenue sides) and cultural fit.

  • Social / Not-for-Profit: the client is a not-for-profit organisation, such as the Government or a charity (e.g., city council looking to improve the quality of life in a city). There is a lot of variability in this type of questions, but there are a few unique considerations, e.g., budget vs revenue, public opinion, donations could be a source of revenue, alignment with the social mission. Always break the question to manageable components (e.g., quality of life in city = air quality, traffic flow, availability of public services, such as schools and hospitals).

  • Capacity expansion: the client is looking to invest in additional capacity. The key is to understand the demand and supply dynamics. Understand the market (size, growth), the competition (market share, capacity, positioning) and the client (current capacity, positioning). Use the data to evaluate whether our client will be able to capture the excess demand and how much of it, and conclude with a financial analysis (ROI, Payback period, NPV).

  • Pricing: the client is looking to set a price for a new product or service. Some common approaches to pricing: Value-based, Cost plus, Market / Competitor based, Target return.

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Step 5: Prepare Fit Stories

Time required: 1-2 weeks

One of the ​most overlooked aspects of case interview preparation is Fit. The intensity of questioning varies significantly between firms with McKinsey being notorious for its PEI "grilling" tactics. The key to succeeding in Fit interview is preparation - be ready to discuss anything on your CV, your motivations for consulting and the specific firm you are interviewing for, as well as examples of leadership, teamwork, conflict resolution, problem solving and perseverance in face of adversity. Even though the Fit interview is separate from the case, candidates are expected to continue communicating in a structured top-down manner. Make sure to select memorable stories that would stand out to the interviewer even after 5-6 interviews that day. Once your stories are ready it is worth testing them with an experienced interviewer.

Simple and useful approach for structuring your Fit stories is the STAR / SCAR framework:

  • Situation: briefly (in 2-3 sentences) provide the context for the story, without going into too many details or industry terms.

  • Task / Complication: describe the problem or conflict and your objective.

  • Action: describe 3-4 specific actions YOU took to resolve the issue or achieve the objective (avoid using "we"), along with the rationale. The bulk of the story should be in this part.

  • Result / Resolution: what was the outcome of your actions. Make sure to include quantified measures, if applicable.

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