Issue Tree
State the question, split it into parts that do not overlap and leave nothing out, then test the parts that would actually change the answer.
Best for a Challenge, a Problem, a Decision · McKinsey, 1960s · takes an hour for the first split
How to run it
- Write one question, singular and answerable. Then write your best answer today, before you start, and who decides what once it is answered. If nobody would do anything differently, swap the question for one where they would.
- Split the question into two to six parts. Test the split: could a fact belong to two parts? Is there a fact that belongs to none? Write down what the split leaves out, and why you cut it this way rather than the obvious other way.
- For each part, say what would have to be true for it to hold, stated so that it could turn out false, and how you would actually test it. "More analysis" is not a test.
- Judge each part: if it holds, does it settle the question, narrow it, or barely move it? Most parts are not decisive. If you have marked them all decisive, you have marked none.
- Open the parts that would change the answer and split them again. Leave the others whole. Depth on the interesting branch instead of the decisive one is the commonest failure.
- Pick the test to run first: the one that moves the answer furthest for the least effort. Give it a date and write down what result would change your mind.
Where it falls down. Perfect MECE is rarely achievable and chasing it wastes time.
With a pen
The questionAnswerable and singular. Best answer today. The decision it informs
BranchWould have to be true / how you’d test it / settles, narrows, barely moves
BranchOverlaps another? Which owns it?
Branch
What this split leaves outAnd why cut it this way
Test firstBy when. What result would change your mind