Comparison of GOMS Analysis Methods

Abstract

Although members of the same family of techniques, the Keystroke Level Model and CPM-GOMS often predict different execution times for the same task [4]. Our data suggest that KLM describes error-tree performance of a skilled user with little practice on a particular task whereas CPM-GOMS describes error-free performance after extensive practice. A participant completed a task 500 times using two different methods. Observed times for the first error-free trial were close to the times predicted by KLM and quickly decreased with practice to more closely match those predicted by CPM-GOMS. The biggest contributor to the change were mental operators, which decreased markedly in both duration and frequency, although the duration of pointing also decreased.