Case Interviews

Case Interviews: Your Detective Adventure 🔍

Imagine you’re a detective. Someone gives you a mystery to solve. You don’t have all the clues yet, but you have a magnifying glass, a notebook, and your brain. Case interviews are exactly like that—you’re solving a business mystery while someone watches how you think!

What is a Case Interview?

Picture this: A lemonade stand owner says, “My sales are down. Help me figure out why!”

That’s a case interview. A company gives you a business problem, and you solve it out loud so they can hear your thinking.

Why do companies do this?

• They want to see HOW you think, not just WHAT you know
• It’s like watching someone build with LEGOs instead of just seeing the final tower

🏗️ Business Case Frameworks

A framework is like a recipe. When you bake cookies, you follow steps. When you solve a case, you follow a framework!

The Big 3 Frameworks

1. Profitability Framework 🍪

“Why are we losing money?”

Profit = Revenue - Costs

Revenue = Price × Quantity sold
Costs = Fixed costs + Variable costs

Example: A toy store is losing money.

• Revenue side: Are fewer kids buying? Did prices drop?
• Cost side: Did rent go up? Are toys costing more to make?

2. Market Entry Framework 🚪

“Should we start selling in a new place?”

Ask these questions like a checklist:

1. How big is the market? (Lots of customers?)
2. Who else is there? (Competition?)
3. Can we do it? (Do we have money and skills?)
4. Will we make money? (Profitable?)

Example: Should a pizza shop open in a new town?

• Are there enough hungry people?
• How many other pizza places exist?
• Do we have enough money to open?
• Will we earn more than we spend?

3. The 4C Framework 🔄

graph TD
    A["Customer"] --> E["Business Decision"]
    B["Company"] --> E
    C["Competition"] --> E
    D["Cost"] --> E

• Customer: Who buys? What do they want?
• Company: What are we good at?
• Competition: Who else is fighting for customers?
• Cost: How much does everything cost?

📏 Market Sizing Questions

These questions ask: “How big is something?”

It’s like guessing how many jellybeans are in a jar—but with logic!

The Secret: Break It Down

Question: How many tennis balls are sold in the US each year?

Don’t panic! Break it into smaller pieces:

Step 1: How many people play tennis?
        → US population: ~330 million
        → Maybe 5% play tennis: 16.5 million players

Step 2: How often do they buy balls?
        → Casual player: 1 can per year
        → Serious player: 10 cans per year
        → Let's say average: 3 cans per year

Step 3: Multiply!
        → 16.5 million × 3 = ~50 million cans
        → Each can has 3 balls = 150 million balls!

Pro tip: Your exact number doesn’t matter. Your THINKING does!

🧩 Case Structuring Approaches

Structuring is like organizing your LEGO pieces before building. Don’t just grab random pieces—sort them first!

The MECE Principle

Mutually Exclusive, Collectively Exhaustive

• Mutually Exclusive: No overlapping (like sorting by color—a piece can’t be red AND blue)
• Collectively Exhaustive: Nothing missing (you have ALL the colors)

Example: Why are sales down?

❌ Bad structure (overlapping):

• Marketing problems
• Advertising issues
• Brand problems (These all overlap!)

✅ Good structure (MECE):

• Revenue issues: Price or quantity problem?
• Cost issues: Fixed or variable costs rising?
• External factors: Economy? Competition? Regulations?

Issue Trees

Think of a tree with branches:

graph TD
    A["Sales are down"] --> B["Revenue Problem"]
    A --> C["Cost Problem"]
    B --> D["Price dropped?"]
    B --> E["Fewer customers?"]
    C --> F["Higher fixed costs?"]
    C --> G["Higher variable costs?"]

Each branch splits the problem into smaller, solvable pieces.

🧮 Mental Math Skills

You can’t use a calculator in case interviews. But don’t worry—there are tricks!

Quick Mental Math Hacks

1. Round to Nice Numbers

• 198 × 5 → Think: 200 × 5 = 1,000 (close enough!)

2. Break Apart Multiplication

• 15 × 12 → (15 × 10) + (15 × 2) = 150 + 30 = 180

3. Percentage Tricks

• 10% of anything: Move decimal left
  • 10% of 450 = 45
• 5% = Half of 10%
  • 5% of 450 = 22.5
• 15% = 10% + 5%
  • 15% of 450 = 45 + 22.5 = 67.5

4. Division Shortcuts

• Divide by 5: Multiply by 2, then divide by 10
  • 350 ÷ 5 → 700 ÷ 10 = 70

Practice Numbers to Memorize

🎤 Presenting Conclusions

You solved the mystery! Now tell the detective chief (interviewer) what you found.

The Pyramid Principle

Start with the answer, THEN explain.

Like a news headline—main point first!

graph TD
    A["ANSWER: We should enter the market"] --> B["Reason 1: Market is large"]
    A --> C["Reason 2: We have capabilities"]
    A --> D["Reason 3: Limited competition"]

Example presentation:

"I recommend the toy store should cut costs by 15% to return to profitability. Here’s why:

First, our analysis shows revenue is stable—customers are still buying.

Second, our rent increased 20% last year, which is the main cost driver.

Third, we could renegotiate the lease or find a smaller location."

The Magic Formula

1. State your recommendation clearly
2. Give 2-3 supporting reasons
3. Mention risks or next steps

Don’t say: “So, um, I looked at lots of things and maybe we should…”

Do say: “Based on my analysis, I recommend X because of reasons 1, 2, and 3.”

🎯 Practice Strategies

You wouldn’t run a marathon without training. Case interviews need practice too!

The 4-Week Training Plan

Week 1: Learn the Basics

• Memorize the 3 main frameworks
• Practice mental math for 15 min daily

Week 2: Solo Practice

• Read cases out loud to yourself
• Time yourself: 2 min for structure, 20 min total

Week 3: Partner Practice

• Find a friend to interview you
• Practice staying calm under pressure

Week 4: Polish

• Record yourself and watch it back
• Focus on clear communication

Practice Resources

The 3 Golden Rules

1. Think out loud — Silence is scary for interviewers
2. Ask clarifying questions — It shows you’re thorough
3. Stay structured — Even if you’re nervous, follow your framework

🌟 Putting It All Together

Remember our detective story? Here’s how it all connects:

graph TD
    A["Get the Case"] --> B["Clarify the Question"]
    B --> C["Choose a Framework"]
    C --> D["Structure Your Analysis"]
    D --> E["Do the Math"]
    E --> F["Present Your Conclusion"]
    F --> G["Answer Follow-ups"]

The journey:

1. Listen to the case carefully
2. Ask clarifying questions
3. Structure your approach (use a framework!)
4. Analyze step by step (show your math!)
5. Conclude with confidence (pyramid principle!)

🚀 You’ve Got This!

Case interviews feel scary, but they’re really just organized problem-solving. Like any skill, practice makes perfect.

Every expert was once a beginner. Every great detective solved their first case.

Now go crack those cases! 🔍✨