Similar to A/B tests, this is testing different labels for same tree category. It is important to only sure one alternative of the tree category per session to user 

Tree Testing: Comparing Labels

Researchers can test different locations of a label. One can test a single tree and compare the number of people who clicked on which main category to find desired subcategory. 

Tree Testing: Comparing Locations

University of Michigan - Ann Arbor

Tree testing focuses on evaluating category labels. This type of study is called "tree" testing because it is assessing hierarchical menus. It is often implemented remotely and unmoderated, and primarily used to follow up card sorting. It also identifies if Information Architecture (IA) structure, labels, and placements align with users’ expectations.

Tree Testing 

Whitenton, Kathryn. “Tree Testing:  Fast, Iterative Evaluation of Menu Labels and Categories.” Nielsen Norman Group, 7 May 2017, https://www.nngroup.com/articles/tree-testing/.

Tree Testing:  Fast, Iterative Evaluation of Menu Labels and Categories

Making comparisons with Tree Testing

- able to evaluate hierarchy based on a real-world scenario
- Because sketching or prototyping  wireframes  of a website or application is not needed, testing can occur very early in design process

Tree Testing: Pros

(1) prepare tree/ hierarchy on excel spreadsheet, listing only one category per row 
(2) create tasks for tree (ex: find a specific product on company's website or test potential problem that a new category may pose)
(3) create instructions that do not give hints to users about the correct categorization and are concise

Tree Testing: Preparation and Formatting

Researchers can use paper prototype if in person or for remote, online softwares such as userzoom.com & Treejack. 

Tree Testing: Tools

- Because it is usually remote and unmoderated, researcher can not ask follow-up questions
- User experience of design can't be tested because no visual styling or mockups are implemented

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