What is SUS

The System Usability Scale (SUS) provides a “quick and dirty”, but a reliable tool for measuring the usability. It consists of a 10 item questionnaire with five response options for respondents; from Strongly agree to Strongly disagree. Originally created by John Brooke in 1986, it allows you to evaluate a wide variety of products and services, including hardware, software, mobile devices, websites and applications.

John Brooke

John Brooke

IT strategy and solutions architecture, SUS methodology creator.

SUS could be used to take a quick measurement of how people perceived the usability of computer systems on which they were working.

John Brooke

John Brooke

IT strategy and solutions architecture, SUS methodology creator.

Although SUS was intended to be “quick and dirty” that refers only to its use; it was constructed with care.

Timeline

  • 1986

    System Usability Scale was invented

    John Brooke I John Brooke made SUS freely available to a number of colleagues, with permission to pass it on to anybody else who might find it useful, and over the next few years occasionally heard of evaluations of systems where researchers and usability engineers had used it with some success.

  • 1996

    First described in a book

    Chapter about SUS was published in book "Usability Evaluation in Industry" In P. W. Jordan, B. Thomas, B. A. Weerdmeester, & A. L. McClelland.

  • 1998

    SUS becomes a part of ISO 9241-11

    John Brook with a group was developing a standard for the definition and measurement of usability ISO 9241, part 11.

  • 1998

    Popularity

    SUS becomes an industry standard

  • 2004

    Tullis and Stetson have shown that it is possible to get reliable results with a sample of 8-12 users

  • 2008

    As Bangor, Kortum, and Miller and Sauro have shown, SUS can be applied to a wide range of technologies, many of which hadn’t been invented when SUS was first developed.

  • 2017

    Usabilitysale.com was born

    Usabilityscale, application for measuring SUS, was invented by Alex Kukharenko and Rudi Thoma.

Key Points

    • SUS is reliable. Users respond consistently to the scale items, and SUS has been shown to detect differences at smaller sample sizes than other questionnaires.

 

    • SUS is valid. That is, it measures what it purports to measure.

 

    • SUS is not diagnostic. That is, it does not tell you what makes a system usable or not.

 

    • SUS scores are not percentages, despite returning a value between 0 and 100. To understand how your product compares to others, you need to look at its percentile ranking.

 

    • SUS measures both learnability and usability.

 

    • SUS scores have a modest correlation with task performance, but it is not surprising that people’s subjective assessments may not be consistent with whether or not they were successful using a system. Subjective assessments of usability are only one component of the overall construct of usability.

 

Credits

  1. “SUS: A Retrospective” by John Brook. Journal of Usability Studies Vol. 8, Issue 2, February 2013.

     

  2. “Measuring usability with the System Usability Scale” by Jeff Sauro | February 2, 2011, measuringu.com.