Abstract
A mathematical model for predicting speed of alphanumeric data entry on small keypads was developed using systems engineering principles. The model included factors for the number of keypresses, the length and direction of each movement, key press and release time, and mental preparation time preceding each character. The model was validated with actual performance data collected from six subjects each using one of three small multifunction keypads based on the touch telephone keyset. Total time to complete the task was predicted reasonably well, but the model failed to correctly differentiate between keypads. The assumptions of the model are discussed in light of the difficulty of modelling the cognitive component of performance.
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