Issue tree

A structured decomposition of a question into its component drivers, each of which can be measured or tested.

Profit decomposes into revenue and cost; revenue into volume and price; volume into customers and frequency. Each split should be mutually exclusive and collectively exhaustive, and each leaf should be something you could actually go and find out.

The tree's value is that it prevents the commonest analytical failure, which is investigating whatever is easiest to investigate. It makes the unexamined branches visible.

Build the tree before gathering any data.