Cross-cultural adaptation, development and psychometric validation of the Libras version of the System Usability Scale

Usability is related to the subjective concept of ease of use and varies according to the user. The participation of deaf people in usability tests is still low. When it occurs, questionnaires in oral language are used, which are not easily accessible to this community. It is necessary to interact with the deaf community on its own terms, respecting its identity and culture, expressed even through the use of sign language. Libras is the official sign language in Brazil. This work carried out the cross-cultural adaptation of the usability assessment questionnaire SUS (System Usability Scale) for Libras. This translation was performed by a multidisciplinary team that included experts in Libras and Software Engineering, and underwent translation quality assessment through the back-translation method. But a recorded version of the SUS in Libras is not enough for the wide application of the instrument, thus, a test system was developed accessible in Libras and Portuguese, which obtained an overall usability score of 68.70 - considered high. This system was remotely tested by 76 volunteer participants, 55 deafs and 21 hearings. Of these, a mixed sample of 23 individuals performed tasks and answered the SUS-Português brasileiro. And a sample of 53 deafs signers and fluents in Libras performed the same tasks and answered the SUS-Libras. Both instruments were evaluated for psychometric properties of internal consistency and criterion validity. The SUS-Português brasileiro obtained a Cronbach's alpha coefficient of 0.93 and Spearman's correlation rs = 0.590 (n = 23, p < 0.001). The SUS-Libras, on the other hand, had a Cronbach's alpha coefficient of 0.72 and a Spearman's correlation of rs = 0.298 (n = 53, p < 0.05), both instruments demonstrated reliability and validity.