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Model-Based Evaluation
Published in Julie A. Jacko, The Human–Computer Interaction Handbook, 2012
As summarized earlier, GOMS is an approach to describing the knowledge of procedures that a user must have to operate a system. The different types of GOMS models differ in the specifics of how the methods and sequences of operators are represented. The aforementioned CPM-GOMS model represents a specific sequence of activity in terms of the cognitive, perceptual, and motor operators performed in the context of a simple model of human information processing. At the other extreme of detail, the Keystroke-Level Model (Card, Moran, and Newell 1980) is likewise based on a specific sequence of activities, but these are limited to the overt keystroke-level operators (i.e., easily observable actions at the level of keystrokes, mouse moves, finding something on the screen, turning a page, and so forth). The task execution time can be predicted by simply looking up a standardized time estimate for each operator and then summing the times. The Keystroke-Level Model has a long string of successes to its credit (see John and Kieras 1996a). Without a doubt, if the design question involves which alternative design is faster in fairly simple situations, there is no excuse for measuring or guessing when a few simple calculations will produce a usefully accurate answer.
Big I Notation to Estimate the Interaction Complexity of Interaction Concepts
Published in International Journal of Human–Computer Interaction, 2022
The keystroke-level model (KLM) predicts the execution times for known task scenarios with keyboards and monitors as interaction devices (Card et al., 1980). The predictions are based on measured average execution times for the specific target user group and operators by using the application for which the predictions will be made. (Card et al., 1983) determined the following average execution times for the operators “P” (pointing with a point device) in 1.10 sec, “K” (press and release key or button) in 0.20 sec., “H” (move hand from mouse to keyboard or the other way around) in 0.40 sec., and “M” (mental preparation and thinking time) in 1.35 sec. The operators are modality specific and independent from user tasks.