What is the System Usability Scale (SUS)?

The System Usability Scale (SUS) is a standardized, post-test questionnaire designed to measure the subjective perception of usability. Developed by John Brooke in 1986, it consists of a 10-item questionnaire with five response options for respondents, based on a Likert scale. It is technology-agnostic and provides a single, global score representing a composite measure of perceived usability. Its simplicity, reliability, and validity have made it a widely adopted industry standard for collecting user feedback on a system's ease of use.

A. This is the formal definition of usability testing itself, as outlined in the ISO 9241-11 standard, not the SUS tool.
B. This describes a usability test task or scenario, which is an activity a participant performs, not a measurement instrument.
D. This defines a usability requirement, which is a criterion or constraint specified for a system, not a method for evaluation.

1. Brooke, J. (1996). SUS: A "quick and dirty" usability scale. In P. W. Jordan, B. Thomas, B. A. Weerdmeester, & A. L. McClelland (Eds.), Usability Evaluation in Industry (pp. 189-194). Taylor & Francis.

Reference Point: In the abstract and introduction (p. 189), Brooke describes SUS as a "ten-item scale giving a global view of subjective assessments of usability."

2. Bangor, A., Kortum, P. T., & Miller, J. T. (2008). An empirical evaluation of the System Usability Scale. International Journal of Human-Computer Interaction, 24(6), 574-594. https://doi.org/10.1080/10447310802205776

Reference Point: The abstract (p. 574) states, "The System Usability Scale (SUS) is a simple, ten-item attitude Likert scale giving a global view of subjective usability."

3. Sauro, J., & Lewis, J. R. (2012). Quantifying the User Experience: Practical Statistics for User Research. Morgan Kaufmann.

Reference Point: Chapter 8, "Standardized Usability Questionnaires," describes the SUS as a "ten-item instrument for the subjective assessment of usability" (p. 186).