Assumption Busting

Purpose

Assumption Busting makes the invisible visible. Every product, strategy, and plan rests on a foundation of assumptions — about users, technology, markets, and behaviour — that are rarely examined. By deliberately surfacing and challenging these assumptions, teams discover that many are untested, some are wrong, and a few, when flipped, unlock entirely new strategic directions.

At a glance

• Group size: 4–12
• Duration: 30 minutes
• Difficulty: Moderate
• Facilitation style: Structured group analysis
• Setting: Workshop room with whiteboard

How to run

1. Identify the subject (3 min): Choose the product, strategy, plan, or concept to examine.
2. List assumptions (10 min): Brainstorm every assumption the subject depends on. Prompt with categories: user behaviour, technology, market, regulation, team capability, timing. Write each on a sticky note.
3. Categorise (5 min): Sort assumptions into: validated (we have evidence), untested (we believe but haven’t verified), and risky (if wrong, the whole plan fails).
4. Challenge risky assumptions (8 min): For each risky assumption, ask: "What if this is wrong?" "What would we do differently?" "How could we test this cheaply?"
5. Plan tests (4 min): Identify the top 2–3 assumptions that must be tested immediately and define a quick experiment for each.

Materials needed

• Sticky notes and markers
• Three-column board: Validated / Untested / Risky
• Whiteboard for assumption challenges

Pitfalls & common mistakes

• Only listing obvious assumptions: Push for implicit, deeply held beliefs that feel "obviously true."
• No categorisation: Without sorting by risk, the team wastes time on assumptions that don’t matter.
• Challenge without action: Identifying risky assumptions without planning tests is intellectual exercise, not progress.
• Doing this alone: Assumptions are blind spots by definition. You need diverse perspectives to surface them.

Inclusion & accessibility

• Use silent writing before group discussion to surface assumptions from all team members.
• Frame assumption busting as learning, not blame — everyone holds assumptions.
• Include assumptions about inclusion itself: "We assume our users are able-bodied / tech-savvy / English-speaking."

Variations

• Assumption reversal: Flip each assumption to its opposite and explore what would change.
• Pre-mortem assumption bust: Frame it as "The project failed. Which assumption was wrong?"
• Stakeholder assumption bust: Map assumptions held by different stakeholders and compare.

When NOT to use this

• When the team is already overwhelmed with uncertainty and needs confidence, not more doubt.
• When the assumptions have already been rigorously tested and the team needs to move forward.
• When used as a delay tactic instead of a genuine critical exercise.

Source & further reading

• de Bono, Edward — *Serious Creativity* (HarperBusiness, 1992)
• Ries, Eric — *The Lean Startup* (Crown Business, 2011) — assumption testing
• Bland & Osterwalder — *Testing Business Ideas* (Wiley, 2019)