想了解使用者對於一個網站是否滿意、是否有助於其解決問題以及是否會想繼續使用等問題，除了透過事後優使性（usability）評分了解使用者對於該網站的看法之外，本研究預期也能透過衡量使用者在操作網站後感受到的整體不確定性（uncertainty）來間接了解使用者對於該網站的優使性看法。
本研究透過文獻探討發展了不確定性與優使性兩份問卷，並招募30位受測者參與測試，受測者須操作8個網站並完成其中的任務後填寫兩份問卷，整個測試過程亦蒐集受測者的操作時間、任務步驟數、過程中的不確定性以及事後訪談等質性與量化資料進行分析，探討不確定性與優使性之間的關係。
研究結果顯示不確定性與優使性有顯著的負相關，且透過偏最小平方法結構方程模型（PLS-SEM）分析後得知，不確定性會對優使性造成負向的影響，若使用者在操作網站後感受到的整體不確定性越高，則其對於該網站的優使性評分就會越低。期望本研究之結果能對於網站效能衡量以及不確定性與優使性關係探討帶來貢獻。

We can find out whether users are satisfied with a website, whether they can solve problems with it, and whether they would like to use it next time by the usability scores of the website, but in addition to understanding users' views on the website through the usability scores, in this study we expect to measure the overall uncertainty that users feel after using the website to indirectly understand the user's view of the usability of the website.
In this study, we developed two questionnaires of uncertainty and usability through literature review, and recruited 30 subjects to participate in the test. The subjects were required to use eight websites and complete two questionnaires after completing the tasks. Qualitative and quantitative data, such as task completion time, task completion steps, uncertainty in the process and post interview, were collected to analyze the relationship between uncertainty and usability.
The results show that there is a significant negative correlation between the uncertainty and the usability. Through the PLS-SEM analysis, it is known that uncertainty will negatively affect usability, if the higher the overall uncertainty that the user feels after using the website, the lower the usability score for the website. It is expected that the results of this study will contribute to the measurement of website performance and the relationship between uncertainty and usability.

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