Maria Vicente A. Bonto-Kane ( mabonto@ncsu ) and Robert St. Amant ( stamant@csc.ncsu )

1. Maria Vicente A. Bonto-Kane (mabonto@ncsu.edu) and Robert St. Amant (stamant@csc.ncsu.edu) Computer Science Department, North Carolina State University, Raleigh, NC 27695 Variance in Execution of GOMS Keyboard Level Operators Show Alternative Directions in Designing and Evaluating Interfaces 1. Problem Statement 3. Results • This research asserts that GOMS’ use of earlier derived mean statistics for task operators has limited applications. GOMS norms need to be updated using better methods of standardization. Earlier mean statistics: • Were derived using total task times divided by number of character sequences, not individual keystroke executions • Were derived on older equipment with slower clock speeds and a limited ability to capture very quick strokes • Do not include norms and variances to allow intelligent decisions when making comparisons and evaluations • Imply executions of operators are the same regardless of contextual conditions when, in fact, productions vary under different task and context conditions ANOVA shows significant differences in mean execution times and variances among different keystroke productions. Paired t-test comparisons show where significant differences lie. 2. Method Subjects were asked to type 1 vs 2 letter sequences under conditions of 1 vs 2 fingers using 1 vs 2 hands and doing repeated vs alternating letter sequences. Latencies for individual keystrokes were captured and statistical means and variances compared. Results are shown: 4. Implications 5. Future Directions • Need for updated norms for GOMS task operators • Need to examine variances to determine what is “empirically” better • Directions gained for improving interfaces • Directions for design of newer devices http://www.marivicbontokane.com/research/poster2-Tapia2009-mabk&stamant.pdf