Selection of elements in process schemes on Cathode Ray Tube (CRT). A comparative study between four types of trackballs

Trackballs were compared for best task performance and for optimum value of control/display ratio (C/D-ratio). The time to place the cursor on a target and the error rate were used as performance measures. The subjects (six for each trackball) rated the C/D-ratios used according to their preference. Results show that target dimension does not influence the error rate; with increasing target dimension the positioning time decreases. Performance with one of the trackballs differs strongly from that of the others, this trackball being originally selected for a totally different purpose. No differences in positioning time and error rate are demonstrated between the remaining types. An optimum C/D-ratio is defined.