Estimating Productivity: Composite Operators for Keystroke Level Modeling

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Abstract

Task time is a measure of productivity in an interface. Keystroke Level Modeling (KLM) can predict experienced user task time to within 10 to 30% of actual times. One of the biggest constraints to implementing KLM is the tedious aspect of estimating the low-level motor and cognitive actions of the users. The method proposed here combines common actions in applications into high-level operators (composite operators) that represent the average error-free time (e.g. to click on a button, select from a drop-down, type into a text-box). The combined operators dramatically reduce the amount of time and error in building an estimate of productivity. An empirical test of 26 users across two enterprise web-applications found this method to estimate the mean observed time to within 10%. The composite operators lend themselves to use by designers and product developers early in development without the need for different prototyping environments or tedious calculations.