在現今的科技發展趨勢下，觸碰式螢幕介面的行動裝置越來越盛行，使用觸碰式螢幕介面的裝置時以手指或是筆尖作為輸入端，直接地與螢幕接觸並搭配不同的手勢動作來操作，以現今人機介面的視覺上設計之探討研究中，多以電腦螢幕的顯示方式做為討論之對象，但許多適用於電腦介面的設計原則與規範，如套用於觸控螢幕之介面設計中時，對使用性來說將會是個大問題，因此觸控式螢幕之介面設計議題是不可以忽視的，且以未來科技的發展來看，針對觸控式螢幕作介面設計之探討是有其價值與必要性的。
本研究選擇蘋果公司的iPad平板電腦為研究對象，而目前針對iPad的使用者介面之研究均處於開發中階段，又以使用者介面元件(User Interface Elements)之研究甚少，故本研究選擇針對以iOS作業系統中的彈跳視窗(Popover)作介面設計之討論，根據各年齡族群共45名以績效量測法(Performance measures)進行使用性測試之實驗，探討控件的位置、彈跳視窗的長度以及呈現於彈跳視窗內的字體大小等變項對於在視覺搜尋任務中其反應時間以及正確率的影響。
實驗結果發現，年齡因素確實會影響正確率以及反應時間等績效的表現，年長者的績效表現均不比年青者以及中壯年者，因此需將年齡因素考慮在介面設計之中。當控件置於螢幕下方時具有較好的績效表現。彈跳視窗之設計在不同資訊量情境以及不同年齡層間是有差別的，在短資訊量時，青壯年族群可使用7格長度以上之視窗與15至23 pt的字體大小；年長族群以至少11格視窗長度與21至23 pt字體為佳；在中資訊量適合用9格以上視窗長度，長資訊量則適合7格以上視窗長度，兩者皆可使用17至23 pt字體，但年長者較偏好15格以上視窗長度與21 pt的字體。本研究結果可實際應用於彈跳視窗之設計中以增加其使用性。

Base on the advancement of today's technologies, mobile devices with touch-screen interface are more and more popular. The finger tip was used to as input device, and touching the screen directly with different gestures to operate these mobile devices. Nowadays, some studies of human computer interface evaluated the display layout of computer, and developed principles and standards of interface design of computer. That doesn't means those standards were suitable for using on the touch-screen. Hence, the issues of the interface design for touch-screen should be noticeable, and it is valuable and necessary to investigate the development of the technologies in the future.
In this study, the touch-screen Apple iPad device was selected for evaluation. There is little information available about user interface design for iPad, especially the user interface elements of the iPad. For this reason, this study aims to evaluate the effect of Popover interface design which is one of the UI elements belong to the iOS system. Performance measures were used to evaluate the effect of location, length and font size of the popover in the visual search task. The reaction time and accuracy rate of the 45 subjects from different age group were collected for analysis.
The results showed that there were significant differences in reaction time and accuracy rate between each age group. The worst performances were found in the older group. The findings indicated that the age should be considered in the interface design. Positioning controls on the bottom of the screen showed better performance. Some differences were found in different the amount of information and age group. In the short amount of information situation, it was acceptable when using the popover above 7 cell-length with the font size between 15 to 23 pt for the young and middle-aged group, above 11 cell-length popover with 21 to 23 pt font size for the older group. It was recommended to use the above 9 cell-length popover in the middle amount of information situation, and above 7 cell-length in the large amount of information situation, both with 17 to 23 pt font size, but the older group preferred the above 15 cell-length with 21 pt font size. The finding of this study can provide a set of recommendations for practical application in the design of popover to facilitate usability.

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