Hello there,

Great question!

Background

One preliminary note: Unconventional cases that are not business-related are also used at other companies besides McKinsey. They are used to take out the business noise and really test the thinking of the candidate, which is the case interview's goal anyway. So the rationale is: Why not create an even playing field by posing a question that everyone is equally clueless about?

Success factors

To be successful in these cases, you must have built your frameworking muscle on unconventional case prompts using isolated drills. Take all the time in the world to create a framework, then self-criticize and revise, then repeat.
 

Types of questions

Practically, when receiving an unconventional case prompt you should make yourself aware of the type of case question being asked to make sure your framework follows an adequate logic:

Brainstorming - Usually break down the goal or issue into levers or drivers

Strategic decision - Look for the criteria that would imply a yes/no answer

Profitability/diagnostic - Look for the cause of the problem, then look for solutions and quantify them

Market sizing (or any sizing) - Look for a formula to break down the number to be estimated into numerical drivers

After having mentally clarified the case type, break down the problem as guided by the question type. Make sure:

• that your framework answers the precise case question
• that it is is tailored and relevant to the case topic
• that points below a common higher-level point are of the same type, that means that they can be expressed by a single plural noun (e.g., ‘reasons’ or ‘levers’ - don't mix!)

Some guidance

To build the framework, you should iteratively apply:

• Breaking down points into multiple lower-level points to add depth and concrete ideas for analyses
• Finding neigbouring points to be exhaustive
• Aggregating points that have a joint higher-level point (category) to make the framework easy to communicate and tidy

For learning how to do this in practice, case coaching is a proven method. Look for a coach who provides case prompts and gives written feedback on structuring excercises between sessions since this is, in my experience, particularly effective.

Hope that helps, fingers crossed for all unconventional cases coming your way!

Best,

Gero

(editiert)