A. G. Hauptmann and A. I. Rudnicky. A comparison of speech versus typed input. In Proceedings of the Third DARPA Speech and Natural Language Workshop, pages 219–224, San Matteo, 1990. Morgan Kaufmann. [pdf]
This paper describes a controlled experiment in which the author compared two input modalities: text and speech. The author designed a task where the subjects had to input a number of numeric strings to the computer. They either used their voice, the keyboard or a combination of the two. They used a number of custom made metrics, like the transaction error rate (the number of transactions that were absolutely necessary divided by the total number of transactions); aggregate cycle time (the total time a subject needed to enter a number correctly).
The utterance accuracy results showed that speech requires many more interactions to complete the task than typing. According to the metrics defined typing reported better results in comparison to speech. The author discussed several reasons of why it was the case.
The author showed how speech compares with typing for the entry of digit string tasks. However, the authors cautioned how real world task, requiring more keystroke per syllable, would demonstrate the effectiveness of speech much better.
The authors concluded that depending on the task, speech can have a tremendous advantages for casual users. The more a task requires visual moniotoring of input the more preferable speech will become as an input medium. For skilled typist these relation might be reversed.