What is assumption mapping in UX design?
Assumption mapping surfaces and evaluates the implicit beliefs that underlie design and product decisions. Every design decision rests on assumptions about users, their needs, their behavior, and feasibility. When these assumptions are implicit and unexamined, teams can invest significant resources in directions that fail because a key assumption was wrong. Assumption mapping makes these beliefs explicit and evaluates them on two dimensions: how certain we are the assumption is true, and how consequential it would be if it were wrong.
How does assumption mapping work?
Team members write down the assumptions underlying a proposed design direction on sticky notes. Each assumption is plotted on a two-by-two matrix with certainty on one axis and importance on the other. Assumptions that are highly uncertain and highly important are the risky ones that need to be tested before significant investment is made. Assumptions that are highly certain can be accepted without testing. This prioritization focuses research resources on the assumptions that matter most.
How does assumption mapping connect to the design process?
Assumption mapping is most valuable at the start of a design project, before discovery research is planned, because it identifies which research questions are most important. It is also valuable when evaluating a proposed design direction before committing to development. Lean UX explicitly builds assumption mapping into its process as a precursor to hypothesis formation and experiment design.