Issue trees are basically maps of problems. They give you a clear and systematic way of looking at the problem you need to solve. They help you break down a big problem into smaller, more manageable ones, and prioritize certain parts of the problem. In other words, they're useful for the "divide and conquer" strategy.

Issue trees are also great for communicating about a problem with others since they provide a map of the problem.

There are two basic kinds of issue trees:

1. Problem trees – created by answering "Why?"
2. Solution trees – created by answering "How?"

How to create an issue tree

Problem tree

A good issue tree must cover the whole problem. It has to be rigorous. Here are some basic principles for creating an issue tree.

1. Start breaking down the problem into separate categories/branches.
2. Use the MECE principle: mutually exclusive, collectively exhaustive.
   • Mutually exclusive means there is no overlap between different parts of the tree. Collectively exhaustive means they cover the whole problem.
3. Do not go into the small details (specific hypotheses): focus on capturing the broad categories that make up the problem.
4. Apply the 80/20 rule: focus on the few parts of the problem that are most impactful.
   • This is best to base on data, rather than your own hypotheses.

Solution tree

When you have singled out some specific parts of the problem that you want to focus on, you can follow up with creating a solution tree.

1. Take the problem part you want to focus on and ask "How might we improve/fix this?"
2. Map out potential categories of the solution
3. Generate ideas within each category

The advantage of this structured way of thinking is that working with constraints will actually help you generate more ideas.