Interview frequency: …
Short answer
Open card sorting lets users group topics and name the groups themselves. Closed card sorting asks them to place topics into predefined categories.
Explanation
Open sorting is used early to generate ideas, discover users' mental models, and understand how they naturally categorize information and describe it in their own words. Closed sorting tests an existing categorization structure and whether its proposed labels and categories are clear and logical to users.
Common mistakes
- Using closed card sorting too early, before learning users' terminology.
- Writing cards that contain the same words as the category labels, automatically leading users to the same solution.