Measuring Perceived Usability: The CSUQ, SUS, and UMUX

ABSTRACT

The primary purpose of this research was to investigate the relationship between two widely used questionnaires designed to measure perceived usability: the Computer System Usability Questionnaire (CSUQ) and the System Usability Scale (SUS). The correlation between concurrently collected CSUQ and SUS scores was 0.76 (over 50% shared variance). After converting CSUQ scores to a 0–100-point scale (to match the range of the SUS scores), there was a small but statistically significant difference between CSUQ and SUS means. Although this difference (just under 2 scale points out of a possible 100) was statistically significant, it did not appear to be practically significant. Although usability practitioners should be cautious pending additional independent replication, it appears that CSUQ scores, after conversion to a 0–100-point scale, can be interpreted with the Sauro–Lewis curved grading scale. As a secondary research goal, investigation of variations of the Usability Metric for User Experience (UMUX) replicated previous findings that the regression-adjusted version of the UMUX-LITE (UMUX-LITEr) had the closest correspondence with concurrently collected SUS scores. Thus, even though these three standardized questionnaires were independently developed and have different item content and formats, they largely appear to be measuring the same thing, presumably, perceived usability.

Acknowledgment

Many thanks to members of the IBM User Experience Panel who participated in this study and to the reviewers who volunteered their time to read and comment on the original manuscript.

Additional information

Notes on contributors

James R. Lewis

James R. (Jim) Lewis is a senior human factors engineer (at IBM since 1981), currently focusing on the design/evaluation of speech applications. He has published influential papers in the areas of usability testing and measurement, and is an IBM Master Inventor with 91 US patents issued to date. His books include Practical Speech User Interface Design and (with Jeff Sauro) Quantifying the User Experience.