A prioritization and alignment tool that organizes knowledge into three columns: Certainties (what the team knows for sure), Suppositions (informed hypotheses that need testing), and Doubts (open questions with no current answer). The CSD Matrix surfaces hidden assumptions and focuses research effort on doubts and suppositions most likely to affect design decisions.
Common contexts
- Filling in a CSD Matrix at project kickoff to surface assumptions stakeholders hold as facts
- Using the Doubts column to prioritize which research questions to answer in discovery sprints
- Revisiting a CSD Matrix after research to move resolved doubts into certainties and update the plan
Use when
Run a CSD Matrix at the very start of a project, before any design work begins, with the whole cross-functional team in the room. It's most valuable when the team has been working in the problem space for a long time and has accumulated assumptions that have never been formally challenged.
Avoid when
Don't use a CSD Matrix as a documentation exercise after the project is underway — its value is in creating shared uncertainty before decisions are made, not in cataloguing what was unknown after the fact. A retrospective CSD Matrix generates no actionable research direction.
The Certainties column is often the most dangerous part of the CSD Matrix — the items teams are most confident about are frequently the assumptions most worth testing, because no one has thought to question them.
Real-world examples
- Nubank's UX teams use CSD matrices at the start of discovery sprints to align stakeholders on what is known, assumed, and unknown before committing to research questions.
- AJ&Smart facilitators introduce the CSD matrix in Design Sprint preparation workshops to surface hidden assumptions that could invalidate a proposed solution before prototyping begins.
- Thoughtworks designers document CSD matrices in project kick-off meetings to create a shared baseline that prevents teams from designing around unvalidated certainties.