We’ve talked a few times about being mutually exclusive and collectively exhaustive (or MECE) in your thinking:
First, we’ve seen how being MECE in your thinking helps ensuring that you leave no overlaps (ME) and no gaps (CE). Then we looked at ways to be more MECE. And we’ve also addressed the fundamental issue of MECE thinking in problem solving: Your actual intent is seldom finding answers that are truly mutually exclusive but rather independent because being ME requires a preclusion. So, we introduced the idea that you should be ICE (independent and collectively exhaustive) instead.
I teach graduate students and executives to be better at solving complex problems, and this differentiation between MECE and ICE thinking can sometimes be not so clear. So let’s get back to it.
In short, make the structure of your question map MECE and the nodes, the actual answers to the question, ICE. Let me explain.
Your question map should have MECE branches. Consider the poster child of issue trees, the profitability map, below.
Forcing the branches to be truly ME is good because it prevents redundancies: If you have included an idea in, say, the “revenues” branch, then it won’t appear in the “costs” one. However, the answers (that is, the nodes of the map) are not ME: Maybe you can improve your profitability by increasing your revenues from returning clients and by also decreasing your variables costs. Pursuing one solution does not preclude you from also pursuing the other (assuming you have the resources to do both). These ideas are independent (i.e., one does not require the help of another to be an answer to your key question).
And this is fine, this is what you want: an efficient map (a map without redundancies) leading to a set of elements several of which might be an answer to your question.
For some problems, making your answers be independent will also force them to be mutually exclusive. In the example below, assuming that you are traveling only once from NYC to London and that whichever means of transportation you choose takes you the entire way, choosing a plane, say, precludes you from choosing any other means of transportation.
But this is a characteristic of the problem rather than a property of your solution, so you should not worry about it.
In the end, the structure of your map is MECE. The ideas/nodes are ICE and sometimes MECE.
Chevallier, A. (2016). Strategic Thinking in Complex Problem Solving. Oxford, UK, Oxford University Press.