Tree testing method

Tree testing is a method to evaluate how findable website's content is. It’s also known as ‘reverse card sorting’ or ‘card-based classification’.

Tree testing focuses exclusively on category labels. It’s a very pure form of evaluation that tests the menu structure - in isolation from other interface design elements, content or navigational aids.

Tree-testing exercises can be moderated or unmoderated.

• Moderated tree-testing exercises provide qualitative feedback from users and an insight into the “whys” behind their decisions. In a moderated session users are encouraged to think aloud which can provide a deeper and better understanding of their ways of thinking.
• Unmoderated (remote) tree-testing exercises provide quantitative results, typically drawn from a larger pool of participants. 

Tree testing is usually conducted at an early stage in the design process. It can help validate the effectiveness of the proposed organisation, structuring and labeling of a site. It helps analysis of where a user would expect to find the information they're looking for, what improvements to a site can be made, based on the observed behaviour.

Before starting to prepare a tree-testing exercise, define the objectives of the test.

Define the elements of information architecture to test and improve the whole website or just a part of it, a section or perhaps just one level. 

Defining clearly who are the intended users of your website/section helps ensure appropriate participants. Define the right tasks for them to perform as part of the test. Recruit up to 50 participants for an unmoderated test. 

During a tree test, take the following two points into consideration:

1. the tree, also called the architectural menu
2. the tasks, or instructions participants need to complete

Defining the tree

In order to define the tree, have a complete list of the main content categories and their subcategories (up to the 3rd, 4th or 5th level of the architecture). Even if only testing a specific section of the tree or a specific level, don't exclude the other sections or levels. Include the complete tree in your test, so test participants are not biased towards any particular section from the outset.

Defining the tasks, or scenarios

The tasks participants are asked to complete are just as important as the tree itself. Decide which categories and labels to test. For each category label, or sub-category label to be tested, define the appropriate task or instruction participants should perform, ie to find something specific within that category.

When defining the tasks or scenarios, phrase the task carefully. Instructions should avoid terms that give away the answers (ie avoid using terms that feature within a label, for example). Avoid potentially misleading details.

When defining tasks:

• define at least one correct destination on the tree for each task
• restrict the number of tasks you ask participants to perform to no more than 10 (otherwise results can be skewed where users remember where they’ve seen labels before)
• as mentioned, use different terms from those in the tree (ie avoid giving clues)

The data from a tree test illustrate the various paths that users take to get to specific information or content. The results will also help in assessing:

• Directness – the percentage of users completing the task without hesitation and obtaining the correct answer first time
• Success – the percentage of users who completed the task
• Time – the time it took users to complete a task. 

The number of attempts taken by users to complete a task can indicate which items are difficult to find.

Any personal data that is processed as part of any task relating to the development of the European Commission's web presence must be done so in compliance with Regulation (EU) 2018/1725 of the European Parliament and of the Council of 23 October 2018. 

See this guide's section about data protection for more info.

• https://www.nngroup.com/articles/tree-testing/
• https://www.userzoom.com/blog/what-is-tree-testing-and-why-is-it-important-for-your-sites-ux/
• https://www.userzoom.com/blog/uxguide/10-tips-conducting-successful-tree-testing/
• https://www.optimalworkshop.com/101/tree-testing

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