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Understand and use the system usability scale

Portrait Maximilien Joannides
Maximilien Joannides
7 min read

The best designs are usually simple and easy to use. So, it’s only fitting that SuS, or the System Usability Scale is itself a simple but hugely effective way to measure the usability of your design.

Whether you’re building an app, a website or something else, user testing before you launch will be a huge factor in your success. UX design requires extensive user research, but when it’s done right, you will have a finished product that is intuitive and easy to master.

That, in turn, is likely to result in a product that is quickly adopted and universally loved, and that, in the product world, means success. So, let’s take a closer look at what the System Usability Scale is, where it came from, and how you can use it.

The essential tool for measuring the effectiveness of a system

In 1986, most of us didn’t even have computers at home. But programmers and software designers were already hard at work, creating the framework for the digital world we now live in. In fact, that’s the year the System Usability Scale was created.

John Brooke was the person who created it. Although he intended it to be a simple evaluation tool for early computer systems, when he shared it, the uptake was swift. Soon, his simple questionnaire became one of the most widely used tools for UX design.

Even now, 35 years later, Brooke’s simple SuS questionnaire is widely used around the world.

How the SUS works

Remember how we started this by saying that the best designs are simple? Well, Brooke’s questionnaire embodies that.

It’s made up of just ten questions. Participants in user research studies are asked to answer these questions, and then their answers are used as part of a user report. It’s so simple it almost seems like it should be too easy. But like great products, keeping it simple works.

The questions that make up the SuS questionnaire are based on what’s known as a Likert scale – in other words, you have to rate each one from one to five, with one being the worst and five being the best.

The questions themselves are:

  1. I think that I would like to use this system frequently.
  2. I found the system unnecessarily complex.
  3. I thought the system was easy to use.
  4. I think that I would need the support of a technical person to be able to use this system.
  5. I found the various functions in this system were well integrated.
  6. I thought there was too much inconsistency in this system.
  7. I would imagine that most people would learn to use this system very quickly.
  8. I found the system very cumbersome to use.
  9. I felt very confident using the system.
  10. I needed to learn a lot of things before I could get going with this system.

As you can see, you don’t need any skill or technical knowledge to use this system, and it can be used for nearly any kind of product or tool.

Analyzing the responses to each question helps to show you what you are getting right, and what needs more work, and because it’s so quick and easy, most people are willing to answer the questionnaire. Which means you get a larger sample size to work with.

How to Use the Results of a System Usability Scale Questionnaire

Of course, UX design is a lot more than one questionnaire, and you do want to make sure that you first identify your target customer before you start asking these questions. If you’re building a tool that’s tailored to a particular skillset, profession, or level of technical knowledge, you can’t simply ask anyone these questions and get a clear picture.

So, you will first need to identify the people you most want to get information from before you start using SuS for user research. But provided you have, and once you have collected enough responses to form a clear picture, it’s time to dig into the data.

Here are a few ways this information can help.

Develop your potential by identifying your strengths

If you can, ask people who participated in your SuS user report process if you can contact them with additional questions. Make sure that you segment your data first and ask people who generally liked your product and interface what they liked about the product. This will give you a good idea what people liked, so you can build on that.

how to identify the mistakes that are holding you back

Now approach the segment who generally did not like your product, and who have agreed to provide additional feedback. Ask them to name specific problems they had with the product. This will give you some idea where you need more work on the usability of your product.

Bad targeting: how to know if you're doing it wrong

If your SuS questionnaire results are overwhelmingly negative, it might not be your product that is the problem, but you might be targeting the wrong people. Take a closer look at your assumptions who might need the product and consider that maybe there is a group that is better suited.

Determine If You Need to Include More Support

In some cases, the tool is good, it’s useful, and the group you think needs it does. But it’s still not easy for them to use. Sometimes, even good tools are complicated by nature. In that case, you might not need to change the product, but you might need to include additional training and tech support resources.

Continuous Improvement

There are very few products out there that don’t change over time. Consumer products might change their recipes, or their packaging. Digital products and software add new features and change their design. You only have to use a site like the Wayback Machine to see how much websites have changed over time. So don’t just use a tool like SuS once. Build it into your continuous improvement processes. Ask users what they think when you make changes or get feedback when you add a new feature. Because the SuS questionnaire is so easy to use and fill in, and so adaptable, it can become a valuable part of everything you do.

Keep It Simple

The golden rule for everything, from creating your product to asking users to give you feedback is to keep it simple.

Users should be able to figure out your product quickly and without too much help from you. They should also be able to tell you what they think quickly and easily. If your product is too complex, people won’t use it. If your post use questionnaire is too long and hard to complete, people won’t tell you what they think.

You need to know what people like, hate and are indifferent to in order to improve your product, and build something people love to use. So, keep it simple. Use a tool like the System Usability Scale to get the information you really need, and then ask additional questions if you have to.

User testing is one of the most important things you can do. Ensuring that the product you have created meets customer needs and expectations is critical to your success. So, keep it simple, get the data you need when you need it, and use it to build better products.