| Summary: | 碩士 === 國立臺灣科技大學 === 設計研究所 === 99 === As the touch screen technology becomes mature, it has applied in mobile devices increasingly. Cell phones are the most sophisticated and widely used mobile devices. The purpose of this study is to explore the touch screen keyboard usability of the mobile phone, and to investigate the factors that may impact the keyboard accuracy. This study is intended to conduct an experiment to examine if these factors may impact the keyboard accuracy of the touch screen mobile phone, and if they impact users’ feelings. In the end, the current touch-screen keyboard design and user satisfaction can be improved. Firstly, the author collected the current mobile phone keypad design and input methods to seek the potential improvement opportunity. Secondly, through the comparison of existing interface usability to explore the factors influencing keyboard input accuracy. This study also tries to understand the users’ preferences in order to analyze the changes for improvement and help improve better typing experience.
There are two stages in the experiment including: (1) The first stage is a survey on current mobile phone designed with touch screen keyboard interface. That is, to gather the mobile phone touch-screen keyboard interface relevant design issues including the interface of the button arrangement, the keyboard input method limitations and impacts, and understand users’ preferences and interface design preferences through interviews; (2) The second stage is about verification experiment. That is to summarize the results generated from the previous stage and relevant literatures for the verification experiment. The verification experiment is a 3 (button size) x 3 (gap size) two-factor within-subjects experiment design. In terms of the "button size" variable, there are three levels: (a) button length and width of 4 mm size, 6 mm size and 8 mm size. In addition, the "gap size" variable is also divided into three levels: (a) spacing of 0 mm: no gap between buttons; (b) spacing of 1 mm: reduced 0.5 mm width of each side inward; (c) spacing of 2 mm: reduce 1 mm width of each side inward. Users’ task performance and subjective assessment data are collected through experiments for statistical analyses.
The study results are as follows: (1) Touch screen phone users and non-touch screen phone users have different preferences. The former prefers to the design that is similar to their current phone; non-touch phone users prefer a larger size button design; (2) "Button size" has significant differences on "placement offset" and "error rate". Larger buttons have a lower "offset placement" and "error rate" value; (3) "Gap size" affects the users' judgement of button size and number of buttons; (4) Users prefers to have "gaps" on the keyboard design, but the major influencing factor is "button size"; (5) Users mentioned when the buttons are small, they are forced to concentrate on the required tasks, so the accuracy should be higher. However, according to the analysis of performance results, the 8mm button has the lowest "impact point offset" and "error rate" value. The results show the user's subjective judgments are not consistence; the keyboard design should focus on how to maximize the visual button size. (6) When the single button sensing area is less 6 mm width, the proposed design of the keyboard gap spacing should be as small as possible to improve the touch accuracy. When the single button sensing area is larger than 6mm width, the gap spacing can be adjusted wider. It is recommended to keep the button size visually larger than 6 mm width to increase touch accuracy.
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