A full life-cycle methodology for structured use-centered quantitative usability requirements specification and usability evaluation of websites

World Wide Web has gained its dominant status in the cyber information and services delivery world in recent years. But how to specify website usability requirements and how to evaluate and improve website usability according to its usability requirements specification are still big issues to all the stakeholders. To help solve this problem, we propose a website usability requirements specification and usability evaluation methodology that features a structured use-centered quantitative full life-cycle method. A validation experiment has been designed and conducted to prove the validity of the proposed methodology, QUEST (Quantitative Usability Equations SeT). Its principle is to prove that QUEST has stronger website usability evaluation capability than the most typical existing usability evaluation methods. Apparently, if QUEST’s website usability evaluation capability is established, then its usability metrics can be used to quantitatively specify upfront user usability requirements for websites. In the validation experiment, 7 usability experts and 20 student subjects were recruited to perform 4 tasks on 2 open source calendar websites, WebCalendar 1.0.5 and VCalendar 1.5.3.1; 4 sets of usability data had been collected, which were corresponding to the following 4 usability evaluation methods respectively: expert usability review, traditional user usability testing, SUS (System Usability Scale), and QUEST. According to the experiment results: both the expert usability review and the traditional user usability testing were inconclusive on which of the 2 target websites had better usability; although SUS rated the overall usability of WebCalendar 1.0.5 at 66.00 and VCalendar 1.5.3.1 at 61.75, it was subjective and vague on usability problems; in contrast, QUEST not only rated the overall usability of WebCalendar 1.0.5 at 56.59 and VCalendar 1.5.3.1 at 35.97, but also revealed where the usability problems were and how severe each usability problem was in a quantitative manner. In conclusion, it clearly can be stated that QUEST has stronger website usability evaluation capability than all other 3 most typical existing usability evaluation methods. So, the proposed methodology has been validated by the experiment results.