I was asked a question today (via email) about case interviewing somewhat indirectly by someone going through the interview cycles with management consulting firms.  I weighed in along with a couple of others on what they are all about and how to best approach them.

I have been on both the delivering and receiving end of these types of questions during my time with Arthur Andersen Business Consulting (now mostly part of Bearingpoint).  Although we were not a tier 1 strategy firm like Mckinsey, Bain, etc. we did similar (albeit it cheaper) work and had many of the same approaches, methodologies, and operating models. Here are my two cents on how to best approach the case question.  Feel free to weigh in in the comments about your own experiences:

• The answer is not as important as how you get there.
• Case
  interview questions are an exercise in the employer understanding how
  you think and you showing off how you can apply a structured framework
  to solving a problem where you have minimal information.
  

Take this example (one from my vintage):  How many plumbers are
there in the U.S.?  The actual number is not important but
think about how you would calculate this:

• What information
  sources would you use, professional associations, unions, publications,
  blogs, etc.
  
• How would you segment this population – professionals, handymen,
  weekend warriors, etc.
  
• How would you quantify the size and
  growth of the population – demographics, trends like more building
  requires new plumbing/less building requires more maintenance, is this a
  different skill set or one that the same population can use regardless
  of need?
  
• And so on…
  

Consulting is all about taking
imperfect data inputs, structuring them in a salient way, and extracting
some meaningful and actionable insight then managing the process of
using that insight to change strategy, process, or systems.