The Assumption Mapper forces teams to make implicit beliefs explicit and then rank them by how risky and untested they are. The top-right quadrant — high risk, untested — becomes the immediate testing priority.
Which of our riskiest assumptions are still untested?
High uncertainty, lower risk: gather more data before acting
High risk, high uncertainty: validate immediately
Low risk, low uncertainty. Safe to move forward.
High risk but well understood. Keep an eye on it.
Prioritise assumptions by risk and validation status in a 2×2 matrix. High-risk untested assumptions surface at the top for immediate testing; validated low-risk ones give you confidence to proceed.
Published in Testing Business Ideas (Wiley). Prioritises which assumptions to validate first.
Start by brain-dumping every assumption your team holds — about customers, the problem, the solution, and the business model. Rate each on importance (how critical if wrong?) and confidence (how much evidence?). Focus testing on high-importance, low-confidence assumptions first.
Don't confuse assumptions with facts — if you have solid evidence, it's not an assumption. Avoid rating assumptions based on gut feel alone. Don't skip validating "obvious" assumptions — those are often the ones that kill products.