On the dimensionality of the System Usability Scale: a test of alternative measurement models.
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.
Borsci
Simone
S
ECoNA, Interuniversity Centre for Research on Cognitive Processing in Natural and Artificial Systems, University of Rome 'La Sapienza', Rome, Italy. simone.borsci@uniroma1.it
Federici
Stefano
S
Lauriola
Marco
M
D005260:Female; D006801:Humans; D007858:Learning; D008297:Male; D008962:Models, Theoretical; D011795:Surveys and Questionnaires; D014584:User-Computer Interface; D055815:Young Adult