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System Usability Scale (SUS)

1990
  • John Brooke
Researcher assessing usability of software using System Usability Scale in an office.

(generated image for illustration only)

The System Usability Scale (SUS) is a widely used, reliable 10-item questionnaire for assessing perceived usability. Users rate each statement on a 5-point Likert scale. The responses are then converted into a single score from 0 to 100. Despite its simplicity, it provides a quick and robust measure of a system’s overall usability from the user’s subjective viewpoint.

The System Usability Scale (SUS) was developed by John Brooke in 1986 as a “quick and dirty” tool for usability practitioners. It consists of ten statements, five worded positively (e.g., “I thought the system was easy to use”) and five worded negatively (e.g., “I found the system unnecessarily complex”). This alternating tone helps prevent acquiescence bias. Users respond using a 5-point scale from “Strongly Disagree” to “Strongly Agree.” The scoring is slightly complex: for positive items, subtract 1 from the scale position; for negative items, subtract the scale position from 5. This results in all values ranging from 0 to 4. The sum of these values is then multiplied by 2.5 to obtain the final SUS score, which ranges from 0 to 100. It’s important to note that this is not a percentage; it’s a percentile score. A score of 68 is considered average. Despite its brevity, research has shown SUS to be reliable and valid across a wide range of interfaces, from hardware to software and websites. Its major advantages are that it is technology-agnostic, easy to administer, and provides a single score that is easy to communicate to stakeholders. It is often used after a usability test to capture the user’s overall impression of the system they just used.

UNESCO Nomenclature: 6114
– Psychology, specialities

Type

Software/Algorithm

Disruption

Incremental

Usage

Widespread Use

Precursors

  • The development of Likert scales by Rensis Likert in the 1930s for psychometric measurement.
  • The field of psychometrics, which provides the theoretical basis for creating reliable and valid measurement scales.
  • Early attempts in HCI to quantify user satisfaction and subjective opinions.
  • The need in industrial settings for cost-effective and rapid assessment tools.

Applications

  • benchmarking usability of different product versions
  • comparing usability of competing products
  • tracking usability improvements over time in agile development
  • quick usability assessment in industrial and academic research
  • validating design changes with user feedback

Patents:

NA

Potential Innovations Ideas

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Related to: system usability scale, SUS, usability testing, questionnaire, likert scale, psychometrics, user feedback, perceived usability, quantitative data, user experience.

Historical Context

1950
1990
1990
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1986
1990
2000

(if date is unknown or not relevant, e.g. "fluid mechanics", a rounded estimation of its notable emergence is provided)

Related Invention, Innovation & Technical Principles

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