Abstract
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.