The purpose of this research was to investigate various measurements of perceived usability, in particular, to assess (a) whether a regression formula developed previously to bring Usability Metric for User Experience LITE (UMUX-LITE) scores into correspondence with System Usability Scale (SUS) scores would continue to do so accurately with an independent set of data; (b) whether additional items covering concepts such as findability, reliability, responsiveness, perceived use by others, effectiveness, and visual appeal would be redundant with the construct of perceived usability or would align with other potential constructs; and (c) the dimensionality of the SUS as a function of self-reported frequency of use and expertise. Given the broad use of and emerging interpretative norms for the SUS, it was encouraging that the regression equation for the UMUX-LITE worked well with this independent set of data, although there is still a need to investigate its efficacy with a broader set of products and methods. Results from a series of principal components analyses indicated that most of the additional concepts, such as findability, familiarity, efficiency, control, and visual appeal covered the same statistical ground as the other more standard metrics for perceived usability. Two of the other items (Reliable and Responsive) made up a reliable construct named System Quality. None of the structural analyses of the SUS as a function of frequency of use or self-reported expertise produced the expected components, indicating the need for additional research in this area and a need to be cautious when using the Usable and Learnable components described in previous research.

In this paper we present the UMUX-LITE, a two-item questionnaire based on the Usability Metric for User Experience (UMUX) [6]. The UMUX-LITE items are This system's capabilities meet my requirements and This system is easy to use." Data from two independent surveys demonstrated adequate psychometric quality of the questionnaire. Estimates of reliability were .82 and .83 -- excellent for a two-item instrument. Concurrent validity was also high, with significant correlation with the SUS (.81, .81) and with likelihood-to-recommend (LTR) scores (.74, .73). The scores were sensitive to respondents' frequency-of-use. UMUX-LITE score means were slightly lower than those for the SUS, but easily adjusted using linear regression to match the SUS scores. Due to its parsimony (two items), reliability, validity, structural basis (usefulness and usability) and, after applying the corrective regression formula, its correspondence to SUS scores, the UMUX-LITE appears to be a promising alternative to the SUS when it is not desirable to use a 10-item instrument.