Case Interview Preparation

Case interviews are designed to test how you think, not what you memorized. In consulting and strategy roles, you are expected to break down ambiguous business problems, prioritize what matters, and communicate a clear path to a decision. Strong preparation is less about collecting dozens of frameworks and more about building a repeatable problem-solving approach you can apply under pressure.

This guide focuses on the core skills that consistently drive performance: structuring, profitability analysis, market sizing, and choosing the right business situation frameworks.

What the Case Interview Is Actually Testing

Most case interviews simulate a client problem where information is incomplete, time is limited, and the interviewer wants to see your judgment. Across firms, the evaluation usually centers on four things:

• Structure: Can you create a logical, MECE (mutually exclusive, collectively exhaustive) breakdown of the problem?
• Analysis: Can you work with numbers, interpret data, and connect analysis to decisions?
• Business intuition: Do your hypotheses and questions reflect real-world drivers like pricing, cost behavior, competition, and customer needs?
• Communication: Can you lead the discussion, summarize crisply, and make your reasoning easy to follow?

A candidate who is “right” but disorganized often scores worse than someone who is structured and insightful but imperfect on a calculation.

The Core Skill: Building a Strong Case Structure

A structure is your map. It tells the interviewer you can handle ambiguity and that your analysis will be targeted.

What a good structure looks like

A strong structure is:

• Objective-led: It starts from the decision or goal, not from a generic framework.
• MECE enough to be useful: Perfect MECE is less important than clarity and coverage of major drivers.
• Prioritized: You signal what you will investigate first and why.

A simple way to pressure-test your structure is to ask: “If I analyze each branch, will I be able to answer the question?” If the answer is no, you are missing a key driver or mixing concepts.

A practical structure-building habit

Before you speak, take 30 to 60 seconds to:

1. Restate the objective in one sentence.
2. Identify the key metric (profit, revenue, share, growth, cost per unit).
3. Lay out 3 to 5 buckets that explain that metric.
4. Call out what you will start with and what information you need.

That small pause usually improves performance more than any memorized template.

Profitability Framework: The Workhorse Case Type

Profitability cases are common because they are intuitive, quantitative, and easy to vary. The goal is usually to explain why profit changed, diagnose what is broken, and propose actions.

The essential model

Profit is:

$$\text{Profit}=\text{Revenue}-\text{Cost}$$

Revenue is typically:

$$\text{Revenue}=\text{Price}\times \text{Volume}$$

Costs split into:

• Variable costs (move with volume)
• Fixed costs (do not move with volume in the short term)

That is the backbone. Your job is to translate it into a tailored structure for the client’s situation.

How to diagnose a profitability decline

A clean approach:

1. Clarify the timeline and magnitude: When did profit drop? By how much? Is it a one-time event or a trend?
2. Decompose profit into revenue and cost: Determine whether revenue fell, costs rose, or both.
3. Go one level deeper:

• If revenue is down: price vs volume, and then volume by customer segment, product, channel, or geography.
• If costs are up: fixed vs variable, then major cost categories (materials, labor, logistics, overhead).

1. Identify the root cause and decide actions: Pricing change, mix shift, competitor move, capacity constraints, input inflation, operational inefficiency.

Common pitfalls in profitability cases

• Treating “cost” as a single bucket without separating fixed and variable drivers.
• Ignoring mix effects (selling more low-margin items can reduce profit even if volume rises).
• Jumping to solutions before isolating what changed.

Market Sizing: Estimation With Business Judgment

Market sizing tests your ability to make reasonable assumptions, do clean math, and sanity-check results. You are rarely graded on the “correct” number; you are graded on whether your logic is defensible.

A reliable market sizing method

1. Define the market precisely: Geography, product scope, customer type, time period.
2. Choose a sizing approach:

• Top-down: Start from population or total spend and narrow down.
• Bottom-up: Start from units per customer or locations and build up.

1. State assumptions clearly: Use round numbers and explain why they are reasonable.
2. Calculate cleanly: Keep units consistent and show intermediate steps.
3. Sanity-check: Compare to known reference points (GDP per capita, typical spending patterns, analogous markets).

Example of strong assumptions (without overcomplicating)

If asked to size annual demand for a consumer product, you might segment by:

• Number of households
• Penetration rate (share of households buying)
• Purchase frequency per year
• Units per purchase
• Average price (if asked for revenue)

The strength lies in the logic chain, not in adding more segments than you can defend.

Business Situation Frameworks: Choosing the Right Lens

Not every case is profitability or market sizing. Many interviews involve growth strategy, market entry, product launches, or operational improvement. Frameworks help, but only when adapted.

Market entry

A practical market entry structure often includes:

• Market attractiveness: Size, growth, profitability, customer dynamics.
• Competitive landscape: Major players, differentiation, barriers to entry.
• Capabilities and fit: Client strengths, gaps, brand, distribution, IP.
• Economics and risks: Investment, breakeven, regulatory and operational risks.
• Entry strategy: Build vs buy vs partner, sequencing, pilot plan.

A strong candidate ties each bucket back to the entry decision and identifies “deal-breaker” questions early (for example, regulation or channel access).

Growth strategy

Growth can come from:

• More customers (new segments, geographies, channels)
• More revenue per customer (pricing, upsell, cross-sell, retention)
• New products or services
• M&A or partnerships

The key is to connect options to constraints: capacity, brand positioning, distribution reach, and economics.

Business situation diagnosis

When a company is “struggling” or “underperforming,” a useful structure is:

• External factors (market demand, competitors, regulation)
• Internal factors (product, pricing, cost structure, operations, organization)
• Customer perspective (needs, willingness to pay, churn, satisfaction)

This keeps you from assuming the problem is internal when the market may be shifting.

How to Practice Effectively

Preparation works best when it is deliberate and feedback-driven.

Practice sequence that builds skill

1. Structure drills: Take prompts and build a structure in 60 seconds. Speak it out loud.
2. Math and charts practice: Percent changes, break-evens, weighted averages, and interpreting exhibits.
3. Full cases with a partner: Focus on driving the case, not following.
4. Post-case review: Identify one structural improvement and one communication improvement each time.

What “good” communication sounds like

• You lead with the objective and your plan.
• You summarize after each analysis step.
• You make recommendations with clear support: “Because X and Y, I recommend Z.”

At the end, your conclusion should be a decision, not a recap. A consulting-style close includes the recommendation, 2 to 3 supporting reasons, key risks, and next steps.

Bringing It Together: A Repeatable Approach

A strong case interview performance is built on repeatable fundamentals:

• Start with a clear objective and a structured breakdown.
• Use the profitability framework to anchor financial logic.
• Treat market sizing as a test of assumptions, math discipline, and sanity-checking.
• Select business situation frameworks based on the question, not habit.
• Communicate as if the interviewer is a client: concise, logical, and decision-oriented.

If you can consistently structure well, analyze cleanly, and explain your reasoning, you will be prepared for the majority of consulting and strategy case interviews, even when the prompt is unfamiliar.