Assumption Mapping

Purpose

Every strategy and product idea rests on assumptions — beliefs treated as facts. Assumption Mapping makes these explicit, then plots them on a 2×2 matrix of importance (how critical to success) versus evidence (how much we actually know). The riskiest assumptions — high importance, low evidence — become the top priority for experiments.

At a glance

How to run

1. Frame the idea (3 min): State the strategy, product concept, or decision under examination.
2. Generate assumptions (10 min): Silent brainstorm. Each participant writes assumptions on sticky notes — about customers, technology, market, resources, timing.
3. Share and deduplicate (5 min): Post all assumptions and merge duplicates.
4. Plot on the matrix (8 min): Draw a 2×2: X-axis = Evidence (low to high), Y-axis = Importance (low to high). Place each assumption collaboratively.
5. Identify leap-of-faith assumptions (4 min): The top-right quadrant (high importance, low evidence) holds the riskiest assumptions. Circle them and commit to testing.

Materials needed

• Sticky notes and markers
• Large 2×2 matrix on whiteboard or flip chart
• The strategy or idea documented for reference

Pitfalls & common mistakes

• Confusing assumptions with facts: Challenge every "everyone knows" statement.
• Only listing desirability assumptions: Include feasibility (can we build it?) and viability (can we sustain it?) too.
• Not testing: The map is pointless without follow-up experiments.
• Consensus placement: If the team disagrees on where an assumption sits, that disagreement is itself a signal to test.

Inclusion & accessibility

• Silent brainstorm ensures all voices are heard.
• Use clear, simple language — assumptions can sound academic.
• Make the matrix large enough for everyone to see and interact with.

Variations

• Assumption-Experiment pairing: Immediately design a lightweight experiment for each top-quadrant assumption.
• Customer-Technology-Business triplet: Structure assumptions into three buckets before plotting.
• Traffic-light Assumptions: Simpler version with Green (validated), Yellow (partially validated), Red (untested).

When NOT to use this

• When the idea is already in production and validated by market data.
• When the team is not empowered to run experiments — mapping without testing breeds frustration.
• As a substitute for actual customer research.

Source & further reading

• David J. Bland & Alexander Osterwalder, *Testing Business Ideas* (2019)
• Jeff Gothelf & Josh Seiden, *Lean UX* (2013)
• Strategyzer: Assumption Mapping