No abstract

The present study sought to determine the sensitivity of three alternative approaches to deriving a workload composite measure based upon data gathered using the Subjective Workload Assessment Technique (SWAT) and to determine through the use of multivariate statistical procedures (MANOVA) if anything is to be gained by retaining the individual scale information of SWAT. The three rating scale dimensions of SWAT (time load, mental effort load, psychological stress load) were combined into a single workload composite using three techniques: conjoint measurement; a simple sum of the three scales weighted equally; an empirically determined weighted-linear combination of the three scales (from MANOVA). Using data gathered by having subjects perform a continuous memory task under twelve levels of task difficulty, it was found that the three composite measures were equally sensitive and highly correlated (the minimum correlation among the three composites being 0.9913). The results of the MANOVA performed on the same data indicated that the individual scales of SWAT were differentially sensitive to different task demands and that individual scale information should be retained rather than rely on a simple composite.

Twelve subjects performed the airplane task, a test of spatial ability, in order to determine whether or not the task is suitable for inclusion in the CTS battery. Subjects performed 12 trials of the task on four consecutive days. Both performance and subjective measures were recorded. Three significantly different loading levels were obtained using the rear, front, and bottom views of the plane. It was concluded that the airplane task appears to be suitable for inclusion in the CTS.

The v a l i d i t y of t h r e e p r o j e c t i v e workload techniques-magnitude e s t i m a t i o n , equal appearing i n t e r v a l s , and t h e s u b j e c t i v e workload assessment technique (SWAT)w a s examined using a simple l a b o r a t o r y task. Ratings of workload by s u b j e c t s who received only w r i t t e n and verbal d e s c r i p t i o n s of t h e t a s k ( p r o j e c t i v e group) w e r e compared t o r a t i n g s from s u b j e c t s who performed t h e t a s k (experimental group). R e s u l t s i n d i c a t e d t h a t , f o r a l l r a t i n g s c a l e techniques, s u b j e c t s were a b l e t o v a l i d l y p r o j e c t r a t i n g s of workload. Magnitude e s t i m a t i o n possessed a higher degree of correspondence between both groups than t h e o t h e r two scales. This f i n d i n g o f f e r s workload r e s e a r c h e r s involved w i t h system predesign c o n s i d e r a t i o n s more o p t i o n s i n the choice of an a p p r o p r i a t e proj e c t i v e workload metric.