Subjective Workload Assessment and Effect of Delayed Ratings in a Probability Monitoring Task

In this investigation, twenty-four subjects performed a probability monitoring task under two difficulty levels and rated the workload associated with each using the Subjective Workload Assessment Technique (SWAT). Measures of response accuracy and response time in the monitoring task were also recorded. The effect of delaying SWAT ratings for both 15 and 30 minute intervals after task completion was also investigated. Study results indicated that SWAT was sensitive to the two levels of probability monitoring task difficulty, but not as sensitive as response accuracy. SWAT was, however, more sensitive to the varying levels than response time. Although there were no statistically significant effects associated with the interval between task completion and assigning ratings, five of the sixteen subjects who gave delayed ratings indicated that workload associated with the more difficult task was lower than the workload associated with the easier task. This finding may be interpreted as evidence that there may be practical consequences when ratings are delayed beyond task completion. The results, in general, are interpreted as supporting the applicability of SWAT as a sensitive workload measure.