Data Entry for Mobile Devices Using Soft Keyboards: Understanding the Effects of Keyboard Size and User Tasks

As mobile, handheld computing devices become more common and are used for an ever-increasing variety of tasks, new mechanisms for data entry must be investigated. Personal digital assistants often provide a small stylus-activated soft keyboard, as do some mobile phones that include touch screens. However, there is little data regarding the importance of keyboard size or the users' tasks, the effectiveness of these keyboards, or user reactions to these keyboards. In this article, an experiment designed to investigate these issues in the context of a palm-style QWERTY keyboard is described. In this study, 30 novices completed 6 realistic tasks using either a small, medium, or large soft keyboard. The results not only confirm that keyboard size does not affect data entry rates but that making the keyboard smaller does not increase error rates or negatively impact preference ratings. However, tasks that required users to switch between the alphabetic keyboard and the numeric keyboard do result in significantly slower data entry rates. A model that accurately predicts the time required to enter predefined text is presented, and directions for future research are discussed.