Application of Conjoint Measurement to Workload Scale Development

Abstract

W r i g h t -P a t t e r s o n A i r Force Base, Ohio ABSTRACT A i r Force Aerospace Medical Research L a b o r a t o r y P r a c t i c a l c o n s i d e r a t i o n s make s u b j e c t i v e o p i n i o n one o f t h e most w i d e l y used methods t o assess mental workload. However, t h e v a l u e o f t h e d a t a o b t a i n e d by s u b j e c t i v e methods i s o f t e n l i m i t e d because s c a l e s a r e n o t s t a n d a r d i z e d and a r e n o t based on modern psychometric p r i n c i p l e s . T h i s paper d e s c r i b e s t h e development and v a l i d a t i o n o f a S u b j e c t i v e Workload Assessment Technique (SWAT) w h i c h uses c o n j o i n t measurement t o c o n s t r u c t i n t e r v a l l e v e l workload s c a l e s f r o m o r d i n a l r a n k i n g s o f combinations o f l e v e l s on t h r e e c o n t r i b u t o r y dimensions. An exDeriment was conducted t o i n v e s t i a a t e t h e c o n s t r u c t v a l i d i t v and c o n c u r r e n t v a l i d i t y ' o f t h e e c t o r group o f s u b j e c t s completes a s c a l e development phase and an e v e n t s c o r i n g phase. D u r i n g t h e s c a l e development phase, d a t a necessary t o develop a workload s c a l e a r e o b t a i n e d f r o m a group o f s u b j e c t s . D u r i n g t h e e v e n t s c o r i n g phase, s u b j e c t s r a t e t h e workload a s s o c i a t e d w i t h a p a r t i c u l a r t a s k and/or m i s s i o n segment. These a r e two d i s t i n c t e v e n t s and o c c u r a t d i f f e r e n t t i m e s . The e n t i r e SWAT procedure i s base upon an a p p l i c a t i o n o f a psychometric t e c h n i q u e known as c o n j o i n t measurement (Coombs e t a l , 1970, K r a n t z and Tversky, 1971). In c o n j o i n t measurement t h e j o i n t e f f e c t s o f s e v e r a l f a c t o r s Recommendations f o r f u r t h e r developme& a r e a r e i n v e s t i g a t e d and t h e r u l e o r c o m p o s i t i o n p r i n c i p l e t h a t r e l a t e s t h e f a c t o r s t o one another i s e x t r a c t e d f r o m t h e d a t a . One major advantage o f c o n j o i n t measurement and r e l a t e d s c a l i n g procedures i s t h a t o n l y t h e o r d i n a l aspects o f t h e d a t a a r e r e q u i r e d f o r t h e p r o d u c t i o n o f an i n t e r v a l l e v e l s c a l e which r e p r e s e n t s t h e j o i n t e f f e c t o f t h e f a c t o r s . The c a p a b i l i t y t o d e r i v e i n t e r v a l l e v e l d a t a f r o m s u b j e c t i v e judgements r e p r e s e n t s obvious advantages o v e r o r d i n a l l e v e l d a t a which t y p i c a l l y r e s u l t f r o m s u b j e c t i v e r a t i n g s . Because o n l y o r d i n a l p r o p e r t i e s o f t h e d a t a a r e needed t o generate a scale, t h e f i r s t s t e p i n t h e procedure i s t o o r d e r t h e dependent v a r i a b l e as a f u n c t i o n o f t h e j o i n t e f f e c t o f t h e f a c t o r s b e i n g i n v e s t i g a t e d . For example, degree o f workloa...

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