39.1 Why Full Cases Are Not Enough
Imagine that your main weakness is structuring. If you complete five full cases, you may practice creating an initial structure only five times.
In the same amount of time, a focused structure session might allow you to work through 15 or 20 different prompts.
Key principle: Full cases test integrated performance; drills build individual skills.
The most efficient preparation combines both. Use drills to repair weaknesses, then use full cases to test whether those improvements hold under realistic pressure.
39.2 Structure Drills
Take a business prompt, give yourself one or two minutes, and build a tailored structure without solving the entire case.
Practice different problem types such as profitability, growth, market entry, operations, pricing, and unfamiliar situations.
Afterward, ask:
- Relevance: Does every branch connect to the objective?
- Completeness: Did I miss a major driver?
- Specificity: Is the structure tailored to this client?
- Prioritization: Can I explain where I would start?
39.3 Hypothesis Drills
Use short case prompts and practice forming an initial hypothesis based on limited information.
Then identify what evidence would support or disprove it.
Example: If profit is declining despite stable revenue, hypothesize that costs are increasing and identify which cost data you would want to examine first.
The objective is not to guess correctly. Practice forming testable views and updating them quickly.
39.4 Clarifying-Question Drills
Read a case opening and decide which questions are genuinely necessary before structuring.
Limit yourself to a small number.
Ask: Is the objective clear? Is the scope clear? Are there material constraints or definitions that would change my approach?
This drill helps prevent both extremes: asking no clarifying questions and asking so many that you delay the case.
39.5 Market-Sizing Drills
Choose everyday markets and build an estimation approach without researching the answer.
Examples include annual movie tickets sold in a city, coffee consumed on a university campus, or the market for home internet in a country.
Practice: Define the market, build the equation, make defensible assumptions, calculate, and sanity-check the result.
Vary between top-down and bottom-up approaches.
39.6 Mental-Math Drills
Practice the arithmetic that appears most often in cases:
- Percentages: Percentage changes and percentage-point differences.
- Multiplication: Large numbers and decimals.
- Division: Ratios and per-unit economics.
- Business formulas: Margins, breakeven, market share, and growth.
Track both speed and accuracy: Fast arithmetic is not useful if errors are frequent.
39.7 Exhibit Drills
Use charts, tables, and graphs from cases or business reports and give yourself a limited amount of time to interpret each one.
Practice stating:
- Headline: What is the main pattern?
- Evidence: Which numbers support it?
- Implication: Why does it matter?
Avoid simply describing every data point.
39.8 Brainstorming Drills
Pick an open-ended question such as, “How could an airline increase customer loyalty?” or “How could a hospital reduce waiting times?”
Give yourself 30 seconds to create categories and then generate ideas within them.
Goal: Produce structured breadth first, then develop the strongest ideas one level deeper.
Practice prioritizing the ideas at the end.
39.9 Business-Judgment Drills
Choose a company or industry and ask practical questions about how it works.
For example:
- What drives revenue?
- What are the major costs?
- Why do customers choose one provider over another?
- What limits growth?
- What would competitors likely do?
Purpose: Train yourself to identify the economic and operational drivers of unfamiliar businesses quickly.
39.10 Synthesis Drills
Take several findings from a case and practice turning them into one concise conclusion.
For example:
Facts: Revenue is stable, labor costs rose $20 million, and logistics costs rose $15 million.
Synthesis: “The profit decline appears cost-driven, with labor and logistics explaining most of the deterioration, so I would focus the next analysis on those two categories.”
Practice connecting finding, implication, and next step.
39.11 Recommendation Drills
Take a completed case or short fact pattern and give yourself 30 to 60 seconds to produce a final recommendation.
Include:
- Answer: What should the client do?
- Evidence: What are the two or three strongest reasons?
- Risk: What could undermine the recommendation?
- Next step: What should happen next?
Record yourself and check whether the recommendation is answer-first and concise.
39.12 Communication Drills
Take questions from previous cases and practice answering them in progressively shorter formats.
Try giving the same answer in two minutes, one minute, and 30 seconds.
Focus: Answer first, number your points, remove filler language, and stop once your reasoning is clear.
Recording yourself is particularly useful because communication problems are often easier to hear afterward than while speaking.
39.13 Combining Drills into Mini-Cases
Once individual skills improve, combine several into short exercises.
A mini-case might include:
- Clarifying the objective.
- Building a structure.
- Completing one calculation.
- Interpreting one exhibit.
- Delivering a short synthesis.
Mini-cases bridge the gap between isolated drills and full interviews while allowing you to repeat the most important skills more frequently.
Final principle: Do not rely exclusively on full cases to improve. Diagnose the skill that is holding you back, isolate it, practice it repeatedly, and then reintegrate it into mini-cases and full cases. Deliberate practice turns vague weaknesses into specific skills you can actually improve.
