Gray, John, & Atwood, 1993

Gray, W. D., John, B. E., & Atwood, M. E. (1993). Project Ernestine: Validating a GOMS analysis for predicting and explaining real-world performance. Human-Computer Interaction, 8(3), 237-309.

Project Ernestine: Validating a GOMS Analysis for Predicting and Explaining Real-world Performance

Project Ernestine served a pragmatic as well as a scientific goal: to compare the worktimes of telephone company toll and assistance operators on two different workstations, and to validate a GOMS analysis for predicting and explaining real-world performance. Contrary to expectations, GOMS predicted and the data confirmed, that performance with the proposed workstation was slower than with the current one. Pragmatically, this increase in performance time translates into a cost of almost $2 million dollars a year to NYNEX. Scientifically, the GOMS models predicted performance with exceptional accuracy.

The empirical data provided us with three interesting results: proof that the new workstation was slower than the old, evidence that this difference was not constant but varied with call category, and (in a trial that spanned four months and collected data on 72,450 phone calls) proof that performance on the new workstation stabilized after the first month. The GOMS models predicted the first two results and explained all three.

In this paper, we discuss the process and results of model building as well as the design and outcome of the field trial. We assess the accuracy of GOMS predictions and use the mechanisms of the models to explain the empirical results. Lastly, we demonstrate how the GOMS models can be used to guide the design of a new workstation and evaluate design decisions before they are implemented.

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