Usability is a user experience attribute that indicates how intuitive and easy to use a website or product is. Measuring usability allows you to learn if users can accomplish their goals with your product or if they encounter issues that you need to fix. Usability is as much related to the ease of use of a website as it is to how it looks and feels. In this context, aesthetics, useful content, and credibility matter too.
There are a few ways to measure the usability of your product. You can do a System Usability Survey (SUS), analyze Google Analytics data such as conversions or bounce rates on a live website, or run usability testing with prototypes and record metrics that help you improve the user experience.
The advantage of doing usability testing before you release a new product or feature is the ability to detect and fix issues early on. Spending time implementing a faulty design or losing customers over preventable errors can be avoided by running usability testing during the design process.
For a long time, measuring usability metrics had been a painful process, mostly done manually by aggregating the data from every task. If you're a Maze user, you already know that we record and give you these metrics automatically once you finished testing your prototype.
In this article, our goal is to go through a list of essential usability metrics and learn why they're important for the user experience.
The value of measuring usability
You may ask, 'Why do I need to record usability metrics when I can just ask my users what they think about the design?' Simply put, because of the Aesthetic-Usability Effect. This effect occurs when users perceive aesthetically pleasing design as more usable. On these occasions, measuring usability metrics allows you to objectively determine how your design performs as opposed to relying on a subjective understanding of what users say.
Additionally, measuring usability has benefits that go beyond what you'd initially expect. It can help you to:
- Find usability issues that aren't easy to detect. When you're knee-deep into a design project, you're too involved to identify issues that naturally slip when developing a product. Here's where usability metrics come in. For example, when you run usability testing and record a low success rate for task completion or a high misclick rate on a particular screen—it's evident that your users are finding it hard to complete their tasks. Such metrics can pinpoint what you need to improve and help you avoid a poor user experience.
- Track progress between design iterations. Measuring the usability of your design allows you to set goals and track progress when you iterate on an existing feature or product. The metrics are easily comparable: you can see how the feature performed last time, so it's easier to know if the new design is better or worse.
- Get buy-in on design decisions. Sometimes arguing your way around your design choices doesn't help. You want to include a navigation bar, whereas your client or manager doesn't. When design choices are tested and measured with data, arguments become less a matter of preference and more about what's working or not.
3 categories of usability metrics you should track
1. Completion metrics
Completion metrics track if users can successfully complete a task. Each task can be deemed a success or a "fail," and in some instances, an indirect success.
Note: when we refer to 'fails' in usability testing, we mean that the task failed, as we're testing the design and not the users.
What it is: A metric that shows if the user completed the task successfully with the design. In Maze, you can set the expected flow(s) you think users will take through your prototype, and if it coincides with the one users take, the result is a direct success.
Why it's important: If the majority of your users can complete their tasks using the flow you designed, then that's a good measure of usability. When assessing if the completion rate for your tasks is good or bad—context matters. However, studies have shown that, on average, 78% is a good completion rate.
What it is: When a user completes a task yet gets lost during the process or takes another viable path to completion, this is measured as an indirect success.
Why it's important: Sometimes, the flow you designed might not be the one users take through the product. Usability testing can reveal if this happens and expose the most optimal flow of your design.
What it is: Fails are measured when a user doesn't complete the task with the design. Maze records both Give ups (when users give up the task) and Bounces (when users leave the test altogether).
Why it's important: Fails are an indicator that your design needs changing. Excluding reasons such as a user not understanding the usability task or out of control interruptions—measuring fails allows you to locate if there are any significant issues you should fix. In a live product, they may lead to a high bounce rate or exits from a page.
2. Duration metrics
This category of metrics relates to the time users to take to complete a task or the time they spend on a particular screen in the design. Time spent is an essential indicator of usability as more time might mean users are having a hard time finding what they need on a page, are lost in the flow, or don’t understand how to use the product.
Time on screen
What it is: Time on screen measures how long a user spends on a particular screen in your prototype.
Why it's important: Except for pages such as blog posts—where the user might naturally spend more time, a long time spent on screen is an indicator that the user can't find what they are looking for. When time on screen is correlated with metrics such as the misclick rate for that screen, it can reveal issues with the interface, labels, or layout of the page.
Time on task
What it is: Time on task is a metric that measures the duration users take to complete a task.
Why it's important: As with time on screen, the longer the duration, the bigger the probability that users can't find what they're looking for or are lost trying to complete the task they were given. When you record a long time spent on a task, it's important to identify the reason: Is it because users are getting lost through the design, and so, you might need to rework the navigation? Or perhaps it's because they didn't understand the task, in which case rephrasing the question might produce better results. The context in which the metric was recorded matters.
Errors are actions such as clicks or taps that users do on your website or app. Errors can easily be measured by tracking the misclick rate or analyzing heatmaps of your prototype screens.
What it is: The misclick rate is the average number of misclicks outside hotspots or clickable areas in a prototype. They usually occur because users can't find what they're looking for, or expect something to act similarly to other websites.
Why it's important: A high misclick rate indicates that users are confused, or that part of your design is misleading. This might lead to users getting lost or even bouncing on a live website. According to Jakob's Law, users spend most of their time on other websites, so they expect yours to function similarly. Measuring the misclick rate allows you to detect if there's any part of your product that needs an immediate redesign.
Measuring usability through satisfaction
Tracking usability metrics allows you to quickly determine how people are using your website, whether there are issues you need to fix, and how your design performs over time.
Apart from metrics about what users do on your website, you can also measure what they think about your product by asking usability testing questions, such as the Single Ease Question (SEQ). The answers to these types of questions will help you better understand their experience when completing usability tasks. Plus, they can reveal some valuable insights about how to improve your design and explain the recorded metrics.
Task satisfaction metrics can be collected with a rating scale after each task. You can ask users: "On a scale of 1-7, how was your experience completing this task?" and measure user satisfaction for each task in your test.
Alternatively, you can do a System Usability Scale at the end of the test. This survey provides a quick way to measure usability by asking users to rate ten items on a scale from zero to 5, ranging from 'Strongly Agree' to 'Strongly Disagree.'
There are a variety of questionnaires to measure the user experience of your product—thinking about which one best suits your user research needs will help you get the most out of usability testing.
Many times, usability gets side-tracked and becomes something that will be dealt with later on. Tracking the usability of your product with metrics allows you to have a clear understanding of the experience you're providing to your users, and improve it over time.