Cognitive Processing

, Volume 10, Issue 3, pp 193–197

On the dimensionality of the System Usability Scale: a test of alternative measurement models

Letter to the editor

Abstract

The System Usability Scale (SUS), developed by Brooke (Usability evaluation in industry, Taylor & Francis, London, pp 189–194, 1996), had a great success among usability practitioners since it is a quick and easy to use measure for collecting users’ usability evaluation of a system. Recently, Lewis and Sauro (Proceedings of the human computer interaction international conference (HCII 2009), San Diego CA, USA, 2009) have proposed a two-factor structure—Usability (8 items) and Learnability (2 items)—suggesting that practitioners might take advantage of these new factors to extract additional information from SUS data. In order to verify the dimensionality in the SUS’ two-component structure, we estimated the parameters and tested with a structural equation model the SUS structure on a sample of 196 university users. Our data indicated that both the unidimensional model and the two-factor model with uncorrelated factors proposed by Lewis and Sauro (Proceedings of the human computer interaction international conference (HCII 2009), San Diego CA, USA, 2009) had a not satisfactory fit to the data. We thus released the hypothesis that Usability and Learnability are independent components of SUS ratings and tested a less restrictive model with correlated factors. This model not only yielded a good fit to the data, but it was also significantly more appropriate to represent the structure of SUS ratings.

Keywords

Questionnaire Usability evaluation System Usability Scale 

References

  1. Bangor A, Kortum PT, Miller JT (2008) An empirical evaluation of the system usability scale. Int J Hum Comp Interact 24:574–594CrossRefGoogle Scholar
  2. Bentler PM (1990) Comparative fit indexes in structural models. Psychol Bull 107:238–246PubMedCrossRefGoogle Scholar
  3. Bentler PM (2004) EQS structural equations modeling software (Version 6.1) (Computer software). Multivariate Software, EncinoGoogle Scholar
  4. Brooke J (1996) SUS: a 'quick and dirty' usability scale. In: Jordan PW, Thomas B, Weerdmeester BA, McClelland IL (eds) Usability evaluation in industry. Taylor & Francis, London, pp 189–194Google Scholar
  5. Browne MW, Cudeck R (1993) Alternative ways of assessing model fit. In: Bollen KA, Long JS (eds) Testing structural equation models. Sage, Beverly Hills, pp 136–162Google Scholar
  6. Carmines EG, Zeller RA (1992) Reliability and validity assessment. SAGE, Beverly HillsGoogle Scholar
  7. Fabrigar LR, Wegener DT, MacCallum RC, Strahan EJ (1999) Evaluating the use of exploratory factor analysis in psychological research. Psychol Meth 4:272–299CrossRefGoogle Scholar
  8. Hu L, Bentler PM (2004) Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct Equ Model 6:1–55CrossRefGoogle Scholar
  9. Kirakowski J (1994) The use of questionnaire methods for usability assessment (unpublished manuscript). http://sumi.ucc.ie/sumipapp.html
  10. Lewis JR, Sauro J (2009) The factor structure of the system usability scale. In: Proceedings of the human computer interaction international conference (HCII 2009), San Diego CA, USAGoogle Scholar
  11. McDonald RP, Ho MR (2002) Principles and practice in reporting structural equation analyses. Psychol Meth 7:64–82CrossRefGoogle Scholar
  12. Satorra A, Bentler PM (2001) A scaled difference chi-square test statistic for moment structure analysis. Psychometrika 66:507–514CrossRefGoogle Scholar
  13. Widaman KF, Thompson JS (2003) On specifying the null model for incremental fit indices in structural equation modeling. Psychol Meth 8:16–37CrossRefGoogle Scholar

Copyright information

© Marta Olivetti Belardinelli and Springer-Verlag 2009

Authors and Affiliations

  • Simone Borsci
    • 1
  • Stefano Federici
    • 2
  • Marco Lauriola
    • 3
  1. 1.ECoNA, Interuniversity Centre for Research on Cognitive Processing in Natural and Artificial SystemsUniversity of Rome ‘La Sapienza’RomeItaly
  2. 2.Department of Human and Educational SciencesUniversity of PerugiaPerugiaItaly
  3. 3.Department of Psychology of Socialization and Development ProcessesUniversity of Rome ‘La Sapienza’RomeItaly

Personalised recommendations