Why does design experiments fail?

The most common reason design experiments fails: Designing experiments that can only confirm what you already believe. If every possible outcome 'proves' your schema, you haven't designed an experiment — you've designed a ritual. The hardest part of experiment design is specifying, in advance, what result would make you update your model.

The fix: Pick one belief you hold about how something works — your learning process, your team's behavior, your market, your habits. Write it as a falsifiable prediction: 'If [schema] is true, then [observable outcome] should happen when [specific condition].' Design the smallest experiment you could run this week to test it. Write down what result would confirm the schema and what result would disprove it — before you run the test.

The underlying principle is straightforward: Create specific tests that would show you if your mental model is accurate.