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

Area of Science:

• Psychometrics
• Human-Computer Interaction
• Digital Mental Health

Background:

• The System Usability Scale (SUS) is commonly used to evaluate internet-based Cognitive Behavioural Therapy (iCBT) usability.
• The validity of SUS for iCBT, particularly for depression treatment among professionals, requires further investigation.
• This study aimed to assess the factor structure and psychometric properties of the SUS in this specific context.

Purpose of the Study:

• To evaluate the factor structure of the SUS when measuring iCBT usability for depression.
• To determine the reliability and convergent validity of the SUS in a professional user sample.
• To confirm the suitability of the SUS as a measure for iCBT interventions.

Main Methods:

• A sample of 242 professionals across 6 European countries using iCBT for depression completed the SUS.
• Confirmatory Factor Analysis (CFA) was employed to compare different SUS models (one-factor, two-factor, bi-factor).
• Reliability was assessed using omega coefficients, and convergent validity was tested by correlating SUS scores with the Client Satisfaction Questionnaire (CSQ-3).

Main Results:

• The bi-factor model demonstrated the best fit to the data, suggesting a multidimensional structure.
• The SUS exhibited good reliability (ω = 0.91).
• Moderate correlations were found between the total SUS score and CSQ-3 scores, supporting convergent validity.

Conclusions:

• Despite a multidimensional structure, the total SUS score is a valid and interpretable measure for assessing iCBT usability.
• The findings support the use of the SUS by professionals evaluating internet-based mental healthcare interventions.
• The study validates the SUS for measuring the usability of iCBT for depression.