CHAPTER 3

Measures of Text Entry Performance

Jacob O. Wobbrock,     University of Washington, Seattle, WA, USA

3.1 INTRODUCTION

When people encounter a new text entry method, the first question they usually ask is, “How fast is it?” Although speed is a key feature of any text entry method, there is much more that can and should be said. Clearly, accuracy is important and is not entirely independent of speed. Even so, there are different kinds of accuracy, such as accuracy during input, when errors may be made and corrected, and accuracy after input, when the entered text is considered complete. But do speed and accuracy tell us everything? What can we say about how learnable a method is, or how efficient? What measures are applicable to keyboard ...

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