Brainstorming in case interviews: how to give structured ideas quickly

A brainstorming question in a case interview sounds like "What could explain the fall in sales?" or "How else could the client grow?". Interviewers score two things: whether your ideas are organised, and whether they are specific to this client. A long unordered list scores badly even when the ideas are good.

The method

1. Take ten seconds and choose two or three buckets that cover the question.
2. Say the buckets first. "I see three groups: price, volume and mix."
3. Give two or three ideas per bucket, each specific to the case.
4. Prioritise. Say which idea you would look at first and why.

Buckets that work for most questions

Example

"A gym chain's membership is falling. What could explain it?"

"I would split this into reasons outside the company and reasons inside it. Outside: a new low-cost competitor nearby, people moving to home fitness apps, or less disposable income locally. Inside: a price rise, worn equipment or crowded peak hours, or changes to opening times or classes. I would start with competitors, because a new low-cost gym would explain a sharp local fall and is quick to check by location."

That answer takes 30 seconds, has two buckets and six ideas, and ends with a priority.

When the interviewer says "what else?"

It is usually a test of range, not a sign you are wrong. Add a new bucket, not more of the same: "Thinking about it from the customer's side..."

Mistakes

• Ideas with no grouping.
• Generic ideas that would fit any company.
• Stopping without saying what you would check first.