Dimensionality of the system usability scale among professionals using internet-based interventions for depression: a confirmatory factor analysis

Mayke Mol, Anneke van Schaik, Els Dozeman, Jeroen Ruwaard, Christiaan Vis, David D. Ebert, Anne Etzelmueller, Kim Mathiasen, Bárbara Moles, Teresa Mora, Claus D. Pedersen, Mette Maria Skjøth, Luisa Peleteiro Pensado, Jordi Piera-Jimenez, Didem Gokcay, Burçin Ünlü Ince, Alessio Russi, Ylenia Sacco, Enrico Zanalda, Ane Fullaondo ZabalaHeleen Riper, Jan H. Smit

Research output: Contribution to journalJournal articleResearchpeer-review

82 Downloads (Pure)


Background: The System Usability Scale (SUS) is used to measure usability of internet-based Cognitive Behavioural Therapy (iCBT). However, whether the SUS is a valid instrument to measure usability in this context is unclear. The aim of this study is to assess the factor structure of the SUS, measuring usability of iCBT for depression in a sample of professionals. In addition, the psychometric properties (reliability, convergent validity) of the SUS were tested. Methods: A sample of 242 professionals using iCBT for depression from 6 European countries completed the SUS. Confirmatory Factor Analysis (CFA) was conducted to test whether a one-factor, two-factor, tone-model or bi-direct model would fit the data best. Reliability was assessed using complementary statistical indices (e.g. omega). To assess convergent validity, the SUS total score was correlated with an adapted Client Satisfaction Questionnaire (CSQ-3). Results: CFA supported the one-factor, two-factor and tone-model, but the bi-factor model fitted the data best (Comparative Fit Index = 0.992, Tucker Lewis Index = 0.985, Root Mean Square Error of Approximation = 0.055, Standardized Root Mean Square Residual = 0.042 (respectively χ 2 diff (9) = 69.82, p < 0.001; χ 2 diff (8) = 33.04, p < 0.001). Reliability of the SUS was good (ω = 0.91). The total SUS score correlated moderately with the CSQ-3 (CSQ1 r s =.49, p < 0.001; CSQ2 r s =.46, p < 0.001; CSQ3 r s =.38, p < 0.001), indicating convergent validity. Conclusions: Although the SUS seems to have a multidimensional structure, the best model showed that the total sumscore of the SUS appears to be a valid and interpretable measure to assess the usability of internet-based interventions when used by professionals in mental healthcare.

Original languageEnglish
Article number218
JournalBMC Psychiatry
Number of pages10
Publication statusPublished - 12. May 2020


  • Confirmatory factor analysis
  • Depression
  • Internet interventions
  • Psychometric evaluation
  • System usability scale


Dive into the research topics of 'Dimensionality of the system usability scale among professionals using internet-based interventions for depression: a confirmatory factor analysis'. Together they form a unique fingerprint.

Cite this