Investigating the Correspondence Between UMUX-LITE and SUS Scores

The UMUX-LITE is a two-item questionnaire that assesses perceived usability. In previous research it correlated highly with the System Usability Scale (SUS) and, with appropriate adjustment using a regression formula, had close correspondence to the magnitude of SUS scores, enabling its comparison with emerging SUS norms. Those results, however, were based on the data used to compute the regression formula. In this paper we describe a study conducted to investigate the quality of the published formula using independent data. The formula worked well. As expected, the correlation between the SUS and UMUX-LITE was significant and substantial, and the overall mean difference between their scores was just 1.1, about 1 % of the range of values the questionnaires can take, verifying the efficacy of the regression formula.