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Case Study Framework

Market sizing, cost estimation, product design walkthroughs.
Interview & prep

Case study frameworks - a memorised playbook for the interview

Three case types you'll get asked in Nigerian PM, consulting and analytics interviews. Copy the framework, practise 5 times, deliver calmly.

1. Market sizing ("How many X in Nigeria")

  1. Clarify: geography (Nigeria all, Lagos only?), time frame, definition of X.
  2. Top-down or bottom-up. State which approach and why.
  3. Anchor on a known number. Nigerian population 220M, adult population 130M, urban population 60M, banked adults 45M.
  4. Filter through funnels. Segment by demographics, adoption rate, purchase frequency.
  5. Sanity check. Compare against a known analog. "That means 1 in every 30 Nigerians - reasonable given X."
  6. State assumptions clearly. Interviewer scores your reasoning, not your accuracy.

2. Product design ("Design a X for Y")

  1. Clarify user + goal. Who is the primary user? What are they trying to achieve? What are they willing to trade off?
  2. Identify pain points. Walk through today's user journey. Where does it break?
  3. Prioritise 3 problems. Not all pains are worth solving. Pick the biggest impact per effort.
  4. Solution brainstorm. 5-8 solutions in 90 seconds. Do not filter yet.
  5. Prioritise 2 solutions. Use a framework - RICE, weighted score, whatever you know.
  6. Success metrics. What would you measure to know it worked?

3. Metric drop ("X metric is down 20% - why?")

  1. Clarify the metric. Numerator? Denominator? Time window?
  2. External vs internal. Did something change in the market, or with our product?
  3. Segment the drop. By user cohort, geography, device, feature. Where is the drop concentrated?
  4. Funnel diagnosis. Which step in the funnel dropped? Acquisition, activation, retention, referral, revenue.
  5. Hypothesise 3 causes. Rank by likelihood and impact.
  6. Propose a validation test. Cheapest experiment that tells you which cause is right.

How to practise case interviews

Do not read cases. Do cases. Book 3 hours with a friend and take turns interviewing each other. The first case will feel awkward. By the fifth you will be smooth. Recording your voice back to yourself is uncomfortable but works - you catch every "um", every dead-end, every place you jumped past a step.