由於觸控技術的成熟，觸控技術運用在行動裝置上的比重越來越重。行動電話則是行動裝置中最成熟也最多人使用的裝置。本研究目的針對觸控行動電話鍵盤介面的使用性進行研究，探討影響觸控行動電話螢幕鍵盤介面準確性因素，並進一步探討影響介面準確性因素是否影響使用者的體驗感受，以改善目前觸控行動電話螢幕鍵盤之介面設計，提昇使用者的滿意度。先探討目前手機上所使用的各式鍵盤設計以及輸入方式，在使用上是否有改善的空間，再透過現行軟體的比較，探討影響鍵盤輸入準確度之因素。並了解使用者的偏好以分析可供改善的變因。以期能供使用者能夠在輸入文字時，獲得更好的使用經驗。
本研究包含兩部分實驗：（1）現有的觸控行動電話螢幕鍵盤介面調查：了解觸控行動電話螢幕鍵盤介面之問題，包含操作介面之按鍵排列、現有輸入法對鍵盤介面設計的限制與影響，並透過訪談了解使用者的偏好與尋求介面設計上之建議；（2）驗證實驗：將前階段之結果，同時整理歸納相關文獻研究，進行驗證實驗。驗證實驗採3（按鍵大小）x 3（間距大小）雙因子受測者內實驗之方式進行。「按鍵大小」之變項共有三層級：（a）按鍵長寬為4公釐大小，按鍵長寬為6公釐大小以及按鍵長寬為8公釐大小。而「間距大小」分為三層級：（a）間距為0公釐：意指按鍵及按鍵之間沒有間隔；（b）間距為1公釐：間距為1公釐，表示各邊寬向內縮0.5公釐；（c）間距為2公釐：間距為2公釐，表示各邊寬向內縮1公釐。透過實驗可獲得操作績效與使用者主觀評量之結果。
研究所獲結果如下：（1）觸控手機使用者對鍵盤設計偏好與非觸控手機使用者的偏好不同。前者偏好與平日使用的鍵盤相似的設計；後者偏好按鍵尺寸較大的設計；（2）「按鍵大小」在「落點偏移量」及「錯誤率」上皆有顯著差異，按鍵尺寸較大者「落點偏移量」及「錯誤率」皆較小尺寸的按鍵來的低；（3）「間距大小」會影響使用者對「按鍵大小」的判斷，在相同尺寸及按鍵數量的範圍裡，有間距的鍵盤設計對使用者來說就是按鍵較小的設計；（4）使用者偏好有「間距」的設計，但對操作準確性的影響程度不若「按鍵大小」來的重要；（5）使用者主觀認為按鍵較小時，會因專心操作任務，所以有較高準確性。但根據績效分析結果，按鍵為8公釐時「落點偏移量」及「錯誤率」皆為最低。可見得使用者的主觀判斷並非事實，鍵盤設計仍應以如何使按鍵視覺上最大化為主要目標。（6）單顆按鍵感應範圍在寬度6公釐以下時，建議鍵盤的間距設計越小越好，以提高操作準確性。若按鍵感應範圍在寬度6公釐以上時，間距大小可以調寬，但建議保持單顆按鍵大小的寬度在6公釐以上，避免降低操作準確性。

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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