Back to basics: Tree Testing explained

What is tree testing?

Tree testing is a user research method that helps you identify how easily users navigate your design. It is an ideal way to evaluate the hierarchical structure of your grouped content, and it provides valuable insights into people’s thought process when exploring a product.

In practice, tree testing assesses how easily people can find information on your tree i.e. a website or app menu, so each task you ask participants to complete will need to have a correct answer. Your users will then need to follow a specific path through a series of accordion menus to find what they are looking for and complete the task(s).

Using a simplified version of your menu devoid of any design elements (opposite to traditional usability testing) ensures your results are not affected by any other factors other than the hierarchical structure.

The quantitative results of a tree test can provide your designers with a chance to zero in on any findability issues, and a wealth of information on how to better structure and organize the topics of your menu.

Why tree

Think of your homepage as a tree trunk, out of which all your topics and subtopics (or insert preferred UX term here) branch out.

The concept of tree testing was first introduced by a design leader named Donna Spencer as a paper-based technique and is also known as card-based classification, or reverse card sorting since you are searching for items instead of placing them in a navigation structure as you do in card sorting.

How it looks

Tree Testing Metrics

When conducting tree testing we gather quantitative metrics. By reviewing such metrics we can see what worked and did not work within the structure of the tree test and understand whether the problems relate to the organizing of the content or the labeling of the categories.

The most common metrics for Tree Testing are explained below.

Success rate: The % of participants who clicked the correct category in the tree for that task
Directness: The % of participants who followed the correct route immediately and clicked the correct category without backtracking 
Time spent: The average amount of time it took participants to complete the task
Path measures: The paths users followed to complete a task and the % of users that followed each of the paths
First click: The categories participants clicked first and the % of participants that did so
Destination: The categories participants ended up clicking as their final answer for a task and the % of users that did so

Tree testing vs. card sorting

These two research methods may both be used to categorize content better, but they have different uses and end goals.

Card sorting is used to procure new ideas when working on a new Information Architecture (IA).

For example, when you are:

• developing a new website or app
• creating a new section on your website
• doing a redesign on your website

Tree testing is used when you already have an IA in mind and want to evaluate it. 

Depending on the development stage you are on:

• Use tree testing to validate the site structure you created with card sorting.
• When redesigning, start with a tree test to get a point of reference.

Tree testing advantages

• As mentioned above, using a simplified version of your site structure ensures results not affected by layout, design, etc.
• Results are easy to analyze. Useberry provides clear visual graphics for each task, thus quickly locating problem areas of your hierarchical structure.
• Minimize findability issues by observing users navigating your site rather than relying on guesswork.
• Remote testing reduces the cost.
• The tests only last a few minutes making recruitment easier
• The tests are relatively quick and cheap, giving you the freedom to run variations and compare results.
• Reliable and repeatable quantitative results.

Tree testing disadvantages

• You can’t rely on tree testing alone. Tree testing is great for revealing issues on your site architecture, but you need to test other aspects of your product to validate overall usability.
• Lack of qualitative data. To resolve this, try polling your users after the fact or do a moderated trial run. Useberry offers many options.

TL;DR
Tree testing is inexpensive and easy to set up and run thanks to testing tools like Useberry. For best results, use it along with card sorting and other complementary tests to get a clear picture of the overall condition of your project.