There are 4 stages of learning anything:

• Stage 1: Don’t know that I don’t know
• Stage 2: Know that I don’t know
• Stage 3: Know that I know
• Stage 4: Don’t consciously realize that I know

So simply searching for stuff we don’t know is not enough. There are things we don’t know that we don’t know. Too bad this is what many of us do to prepare for Case Interview.We need a one-stop place that gives us a big picture. That’s exactly the role of this page. We won’t go too much into the specific content here, but this should act as a “home” and a “map” page for your Case Study Interview studying no matter where you are.

The core logical foundation of how management consultants solve problems

• Element No.1:
  The problem has to be defined
  
  
  
• Element No.2:
  To solve a big problem, we – management consultants don’t look for solutions right away. Instead, we try to find the ROOT-CAUSE. This ensures us tocompletely eradicate  the problem and to have a long-lasting impact.
  
  
  
• Element No.3:
  There can be millions of possible root-causes. To effectively and efficiently find the right one, we use a top-down and MECE approach. This is called an “issue tree”. 
  
  
  
• Element No.4:
  In order for each branch to exist in the issue tree, there HAS to be a chance that the Root-cause is in it. In other words, for every branch, there must be at least one hypothesis associated with it.
  
  
  
• Element No.5:
  Now assume we have a structured, MECE, and hypothesis-based issue tree. Pick the best hypothesis,or,  in other words, choose a big branch to begin with. Then test if the root-cause is in there.
  
  
  
• Element No.6:
  Depending on each case, different methods are used to test hypotheses. But benchmarks are powerful tool. Two main types of benchmarks are historical and competitors’ data.
  
  
  
• Element No.7:
  If data suggests that the root-cause is indeed IN the testing branch, go down one level deeper and repeat the same process: breaking down the branches into sub branches in a MECE, hypothesis-driven way and test each sub-branch using data.
  
  
  
• Element No.8:
  At any point where the data suggests that the root-cause is NOT in the testing branch or sub-branch, move to a parallel branch or sub-branch on the same level.
  
  
  
• Element No.9:
  Keep doing this until the whole issue tree has been covered or until the interviewer would like you to switch gears.
  
  
  
• Element No.10:
  Lastly, once you have identified one or many root-causes, think of solutions to fix  them!

In theory, the above approach always works. But the following two conditions must be met.

• Condition No.1:
  Each and every single part of the issue tree must be perfectly MECE.
  
  
  
• Condition No.2:
  The issue tree, or in other words, the breakdown must somewhat properly isolate the root-cause.
  
  
  

A few tips to meet these conditions:

1. Make sure you understand the concept of MECE really well. 

2. Try to improve your business intuition in order to be able to pick good frameworks or correctly draw spot-on issue trees.

3. Most importantly, develop the habit of aligning with the interviewer. No matter how good you are with the two tips above, there will always be cases that are hard to be MECE inside out and hard to draw frameworks that are spot on. The interviewer is actually a great resource you can use.