What Is the System Usability Scale (SUS) and Why Is It Important?


What Is the System Usability Scale (SUS) and Why Is It Important?

The most innovative and impressive product could be rendered ineffective if it isn't user-friendly.

That's why a key portion of your product development efforts should focus on usability. The only problem? It can be difficult to standardize this concept, as a feature that's accessible for one person might be difficult for another.

Thus, there existed a need to create a scalable system capable of capturing a wide range of user responses. The outcome of this need was the System Usability Scale, or SUS. Developers can leverage the outcomes of their SUS efforts to better understand how certain groups use their products and services.

Today, we're taking a closer look at this scale and what it includes. In addition, we'll also share how to use our online tool to conduct SUS tests of your own, along with how to analyze the data you receive.

Ready to learn more? Let's get started.

What is the System Usability Scale?

Developed by John Brooke in 1986, the SUS takes the complex and often vague concept of usability and simplifies it. The result, as Brooke explained it, is a "quick and dirty" tool that developers across various industries can use to make their products as user-friendly as possible.

The scale itself consists of a 10-item questionnaire. After each question about usability, respondents can choose from five options, ranging from Strongly Agree to Strongly Disagree. Simple and straightforward, SUS helps shed light on how users perceive a variety of products and services, including hardware, software, websites, mobile devices, and applications.

Getting Started with SUS

Are you looking for clearer insights into how to measure usability within your own organization? Doing so can help you control costs, optimize resources and ultimately, deliver a more effective offering.

The best part? Our online SUS tool allows you to complete the process more quickly and efficiently than ever before. Once you sign up, the steps to complete your test are simple. Let's take a look at the process to follow.

Registering for an Account

To access the SUS tool, you'll need to create an account. You can go here to see our different pricing options, as well as our free trial. Our Premium Plan lasts for one month while our Pro Plan lasts for one year. Both options provide the following resources:

  • Access to all usabiliTEST tools
  • Unlimited tests
  • Unlimited participants
  • Built-in analytics
  • Co-branding

Our free trial lasts 48 hours and is a great way to get your feet wet and navigate the system before committing to a plan.

Step 1: Create a New Test

After you log onto your dashboard, you'll see three options as follows:

  • Create new test
  • Invite participants
  • Review test data

Click "Select New Test Type" at the bottom to get started. From that menu, find "SUS+" and click "Create New Test."

Step 2: Enter Test Details

Next, you'll assign a name to your test and give it a description. If you need to complete advanced functions, you can do so at this time. By pressing "Advanced Options", you'll be able to provide exert even greater control of the testing process, defining parameters such as:

  • Test page logo
  • Single or multiple participants per computer
  • Test expiration date
  • Test password
  • Private or shared test results
  • Widget for sharing on social media
  • Option to build a test panel
  • Language preferences

When you're finished, click "Save Test Details."

Step 3: Populate the Questionnaire

As a rule, the SUS centers on 10 questions that John Brooke developed. To achieve accurate results, you cannot edit these questions, though this next step, you can customize them with the name of your product or service.

Click "SUS Questionnaire", assign your given SUS subject, and watch the fields automatically populate. The 10 questions the test asks include:

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

Participants will select an answer between 1 and 5 for each question. A response of 1 means they disagree to the strongest degree, while a response of 5 means they agree to the strongest degree.

At this step, you'll also be able to select whether you want to add an Adjective Rating Scale or Promoter Rating Scale to your test. Let's review what these include and the differences between the two.

Adjective Rating Scale

This is a rating scale supplemental to SUS that asks this question:

  • Overall, I would rate the user-friendliness of this product as _____.

If you select this option, the prompt above will display as Question 11 on your SUS test. Instead of following the standard SUS format, it presents users with a seven-point, adjective-anchored Likert scale that they can reference to choose their answer.

Promoter Rating Scale

Net Promoter Score (NPS) is a management tool that can help companies gauge the willingness of customers to recommend their products or services to others. Using an index that ranges from -100 to 100, it helps assess a user's overall satisfaction and their loyalty to your brand.

If you select this rating scale, you'll see a final question added to the end of your SUS test that reads:

  • How likely is it that you would recommend [your solution] to a friend or colleague?

When you've populated your test and chosen your rating scale options, click "Save SUS."

Step 4: Publish the Test

You've completed the steps to edit the SUS to fit your product. Now, click "Publish." When you do so, you'll receive a direct link to the test that you can share with your test participants.

Along the way, you'll be able to see the number of times the test has been viewed, along with how many people have participated and the average completion rate.

Analyzing Your SUS Results

Once you've distributed your test link and allotted your set amount of time for respondent participation, it's time to analyze the data you collect. Our tool makes it easy to mine your myriad test results for valuable insights, including:

  • SUS score
  • Learnability
  • Usability
  • Standard deviation
  • Cronbach's Alpha
  • Adjective average (if applicable)
  • Net Promoter Score (if applicable)

Your SUS score can be a complex number to understand, so let's take a closer look at how it's calculated.

When each participant answers each question, the scores for that question are between 1 and 5. To calculate your score, follow these steps:

  • On every odd-numbered question, subtract 1 from your score.
  • On every even-numbered questions, subtract that value from 5.
  • Take the new values and sum the total score.
  • Multiply this new number by 2.5.

This way, your number should fall somewhere between 1 and 100. It's important to note that this number is not a percentage of 100.

Industry experts concur that a SUS score of 68 or above is considered average, while any score less than 68 is below average. To interpret your scores more closely, you can normalize them to produce a percentile ranking. In general, the industry consensus is that:

  • An SUS score of 80.3 or higher is excellent, or an A. People love your product or service and will recommend it to others.
  • An SUS score of around 68 is average, or a C. Your product or service is usable, but it could improve.
  • An SUS score of 51 or under is poor, or an F. Your product or service is inaccessible and improving it should be a top priority.

You can use the collected results and your score to help understand where your products succeed, where they're lacking and how you can improve them to make them more usable to your target audience.

Get Started With Our Usability Testing Tools

When it comes to usability testing, there are myriad approaches you can take. An SUS test is one of the quickest, easiest and most cost-effective ways to request and receive clear user data to improve your products and services.

The best part? Our intuitive online tool makes it easy for you to set up as many SUS tests as you need. You can also use the tool to monitor responses in real time and analyze the data you collect.

To get started, sign up for a free trial today. This 48-hour, all-access experience is a great way to see for yourself the difference our approach makes.

Also see:

System Usability Scale (SUS) Plus

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