Tree testing is a usability technique for evaluating the findability of topics in a website. It is also known as reverse card sorting or card-based classification. A large website is typically organized into a hierarchy (a "tree") of topics and subtopics. Tree testing provides a way to measure how well users can find items in this hierarchy. Unlike traditional usability testing, tree testing is not done on the website itself; instead, a simplified text version of the site structure is used. This ensures that the structure is evaluated in isolation, nullifying the effects of navigational aids, visual design, and other factors. Tree testing is a good technique for testing an existing or proposed navigation system.

Tree testing is a method used to evaluate the findability of topics within a website. The test subjects are given a task, such as finding information about a specific product, and then asked to choose where they would expect to find that information from a list of choices. The test administrator then notes which option the subjects chose and whether they were successful in finding the information. This process is repeated for several different tasks to get an overall picture of how well the website's structure works.

Why Use Tree Testing?

Tree testing has several advantages over traditional usability testing methods. First, because it uses a simplified text version of the website's structure, it isolates the evaluation of that structure from other factors such as navigational aids and visual design. This allows for a more accurate assessment of how well the website's hierarchy works. Second, tree testing can be done without having to create a fully functional prototype of the website; all that is needed is a list of topics and subtopics. This makes it an ideal technique for early-stage evaluations when time and resources are limited. Finally, because tree testing does not require actual users to navigate through the website, it can be done relatively quickly and cheaply.

When Not to Use Tree Testing?

Although tree testing has its uses, it is not good for discovery research. Tree tests will only test the structure and taxonomy you are proposing, however they were created, not explore users' mental models. Other card sorting methods work better for this, and probably should be done before a taxonomy is created. Moderated tree testing or tests that encourage and record "think out-loud" methods can be better for gaining more insights into mental models of participants.

Typical Steps for a Tree Test

1. The participant is given a task, usually to find something.
2. They are shown a simple list of the top level topics for the website or taxonomy.
3. The participant chooses the topic and then any subtopics and lower until they either find the task or give up. They can backtrack if they want.
4. The researcher gives them several tasks in this manner.
5. When enough participants have performed the test, the researcher can analyze the results.

Tree testing is an important usability technique that all user researchers should be familiar with. By creating a task list, site map, and recruiting test participants, you can conduct your own tree test and make necessary changes to improve the findability of topics on your website. They are usually easy to run, either moderated or unmoderated and take less time for participants compared to other methods.