The Usability Metric for User Experience
Interacting with Computers, Vol. 22, No. 5, 2010, p.323-327.
This study showed two main results: (1) the Usability Metric for User Experience (UMUX, 4 items) correlate well with the System Usability Scale (SUS, 10 items), they are reliable and aligned on one underlying usability factor; and (2) the UMUX is compact enough to serve as a usability module in a broader user experience metric.
The UMUX is a four-item Likert scale used for the subjective assessment of an application’s perceived usability. It is designed to provide results similar to those obtained with the 10-item SUS, and is organized around the ISO 9241-11 definition of usability.
How candidate Likert items would fare in an analysis of actual responses to items; and is UMUX comparable with SUS?
1. Pilot study: 42 participants engaged in a usability test of an enterprise software prototype involving the selection of contract workers and adding them to a database. 2. Survey study: 558 participants used either the UMUX or the SUS; and then responded to both instruments.
42 for the pilot study; and 558 for the survey study.
A five-point scale test was used for the pilot study; and a seven-point scale and survey to compare the two instruments was used for the survey study.
The pilot study identified the three most promising candidates to be included in a measurement instrument along with an additional ease of use item from the UMUX. When combined into a preliminary user experience inventory, the four candidate items met the research program’s goal of a correlation higher than 0.80 with the SUS. The compact size of the UMUX is suited to a more fully realized measurement model of user experience. Such a model would go beyond Product Use, and would include other product lifecycle stages such as Brand Awareness and Installation. The UMUX is well positioned as a foundation for developing future instruments, with the ultimate goal of metrics that can target any of a product’s user experience aspects in a way that is concise and cross-validated.