The most effective way of understanding what works and what doesn’t in an interface is to watch people use it. This is the essence of usability testing.
In order to assess the usability of an interface, we ask testers to carry out a number of tasks using the interface. To watch people try to use what you are building, you need to give them something to do. It’s a two-step process:
- First you choose the tasks to test.
- Then you expand the tasks into scenario tasks — the little scripts that set the stage for the action and provide a bit of explanation and context.
The first step is to come up with a list of general user goals that visitors to your site or application may have. Ask yourself: What are the most important things that every user must be able to accomplish on the site?
As a quick example, here’s a list of tasks for youtube:
Search for a video.
Watch a video.
Create a playlist of videos.
Once you’ve figured out what the users’ goals are, you need to formulate scenario tasks that are appropriate for usability testing.
Task: Search for a video.
Scenario task: You’ve heard from your friend that Coldplay released a new music video. You want to see it. Find the video on youtube.
A scenario task has the character, the context and the necessary details that the user needs to know, but doesn’t. Scenario tasks resemble those that users would perform in a real life context. A well-crafted scenario task will help you to uncover usability issues more effectively.
Tips for writing scenario tasks
Make the scenario task realistic.
Make sure that each scenario task is realistic and typical for how people actually use the system, when they are on their own time, doing their own activities.
Avoid giving clues.
Phrase your scenario tasks without uncommon or unique words that appear on the screen. If you do, you turn the tasks into a simple game of word-finding.
Keep the scenario task concise.
Provide the participants with the information that they need to complete a task, and trim every detail that doesn’t contribute.