title: Quantifying usability: an evaluation of a diabetes mHealth system on effectiveness, efficiency, and satisfaction metrics with associated user characteristics.
abstract: OBJECTIVE
  Mobile health (mHealth) systems are becoming more common for chronic disease management, but usability studies are still needed on patients' perspectives and mHealth interaction performance. This deficiency is addressed by our quantitative usability study of a mHealth diabetes system evaluating patients' task performance, satisfaction, and the relationship of these measures to user characteristics.
  
  
  METHODS
  We used metrics in the International Organization for Standardization (ISO) 9241-11 standard. After standardized training, 10 patients performed representative tasks and were assessed on individual task success, errors, efficiency (time on task), satisfaction (System Usability Scale [SUS]) and user characteristics.
  
  
  RESULTS
  Tasks of exporting and correcting values proved the most difficult, had the most errors, the lowest task success rates, and consumed the longest times on task. The average SUS satisfaction score was 80.5, indicating good but not excellent system usability. Data trends showed males were more successful in task completion, and younger participants had higher performance scores. Educational level did not influence performance, but a more recent diabetes diagnosis did. Patients with more experience in information technology (IT) also had higher performance rates.
  
  
  CONCLUSIONS
  Difficult task performance indicated areas for redesign. Our methods can assist others in identifying areas in need of improvement. Data about user background and IT skills also showed how user characteristics influence performance and can provide future considerations for targeted mHealth designs.
  
  
  CONCLUSIONS
  Using the ISO 9241-11 usability standard, the SUS instrument for satisfaction and measuring user characteristics provided objective measures of patients' experienced usability. These could serve as an exemplar for standardized, quantitative methods for usability studies on mHealth systems.
authors.affiliation: Department of Biomedical Informatics, University of Utah, Salt Lake City, Utah, USA Faculty of Computing, Blekinge Institute of Technology, Karlskrona, Sweden mattias.georgsson@bth.se.
authors.forename: Mattias
authors.initials: M
authors.lastname: Georgsson
authors.affiliation: Department of Biomedical Informatics, University of Utah, Salt Lake City, Utah, USA School of Nursing, University of Maryland, Baltimore, Maryland, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Staggers
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D003258:Consumer Behavior; D003920:Diabetes Mellitus / Q000628:therapy*; D004526:Efficiency; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction; D012648:Self Care; D017216:Telemedicine / Q000592:standards; D014584:User-Computer Interface
keywords: diabetes; mobile health; self-management; usability evaluation; user-centered design