本研究為透過使用者測試的方法，瞭解不同年齡層的使用者以掐捏手勢在多點觸控螢幕上進行縮放操作時目標顯示的密度、螢幕尺寸以及控制/顯示增益(C/D gain) 對於最適目標尺寸的效應以及目標點選的績效影響。
本研究募集了20位使用者(10位年輕人和10位老年人)，在3種尺寸(5寸、7寸、10寸)的觸控螢幕上進行縮放目標按鍵大小並點選的實驗。實驗中設計了3組不同動態的控制顯示增益(C/D gain=0.5、1、2)條件、4種不同目標顯示密度(DIV=0、0.5、1、2)，並在各種條件下收集最適目標尺寸大小(MATS)，並與偏離值(Deviation)和操作時間(Time)進行後續的分析。
實驗結果顯示，MATS的平均大小約為5.5mm。MATS大小根據不同年齡層，年輕人約為4.1mm、老年人約為6.9mm。我們發現MATS在7寸的螢幕上最小(5.23mm)、在10寸的螢幕上最大(5.66mm)，C/D gain愈快、目標顯示密度愈大則MATS愈大；另外MATS大小與偏離值呈現正相關。在實驗結果中不同年齡操作時間的差異不顯著，顯示可縮放界面改善了高齡者的時間操作績效。本研究的結果可提供觸控介面工程師/設計師，在不同操作條件下設計按鍵或目標大小作為參考。未來建議在實驗室中，可精確的量測手持距離(觀視距離)與操作時間的組成成分(縮放時間與點選時間)，對本研究所提出的假設機制加以驗證。

Through user experiment, this study aimed to know the effects the Density, Display size, and C/D gain on the Most Appropriate Target Size (MATS) and the performance, from users of different ages using pinch gestures to zoom and click on targets with a zoomable interface on a multi-touch screen.
Twenty participants (10 young and 10 elder adults) were recruited to perform the zoom-and-click experimental task on portable touch devices of three display sizes (5-inch, 7-inch, 10-inch). The experimental task was carried out under three different C/D gain (CDG=0.5, 1, 0), four kinds of different Density (DIV = 0, 0.5, 1, 2) and two bonus conditions to collect the most appropriate target size (MATS) together with the deviation from the target center (Deviation) and the operating time (Time) for subsequent analysis. The results showed that the average MATS was about 5.5mm. For users of different ages, the MATS for young people was about 4.1mm and for elder people was about 6.9mm, respectively. MATS on 7-inch (5.23mm) display was found to be smallest, while that on 10-inch (5.66mm) display was biggest. And MATS increased significantly with higher CDG and density. Age did not induce significant effects on operation time, meaning the zoomable interface improve the elder person’s time performance.
The results of this study may provide design guidelines to touch interface engineer/ designer under different conditions for optimal button or target size. Future studies are suggested to accurately measure the handheld distance of devices and divide operating time into zooming and clicking time to verify the hypotheses proposed in this study.

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