9th International Conference on Design, User Experience, and Usability, DUXU 2020, held as part of the 22nd International Conference on Human-Computer Interaction, HCII 2020, Copenhagen, Denmark, 19 - 24 July 2020, pp.294-312
© 2020, Springer Nature Switzerland AG.The ongoing and enduring adoption of mobile devices with ever-enlarging screens continues to bring new challenges in application development to improve usability. This study aims at providing insights on efficiency, effectiveness and user satisfaction of four leading food and grocery delivery applications in Turkey, when they are used with a single hand on a phablet. We designed a usability test with qualitative and quantitative aspects based on a multi-method approach with a sample of 9 male and 9 female university students from Istanbul. The participants were observed during the execution of 21 tasks on food delivery applications Yemeksepeti and GetirYemek, as well as their inter-linked online groceries, Banabi and Getir. Additional data was collected by the thinking-aloud protocol, video recording, a post-test interview, a System Usability Scale (SUS) survey and anthropometric measuring. By averaging together a standardized version of completion rates, task-times, task-level satisfaction and errors, we also generated Single Usability Metric (SUM) scores for each application. Results were discussed in the dimensions of ergonomics, findability, discoverability and use of conventions. Although all applications scored higher than 78% in 18 of the 21 tasks in Single Usability Metric (SUM) with a confidence level of 90% and 52 error opportunities, their SUS scores were between 54%–74%. Together with this finding, the fact that 9 tasks received lower than 50% in user satisfaction on SUM was used to assert that there was still room to improve one-handed usability of mobile applications.