A NEW APPROACH TO CATEGORY SCALES OF INTENSITY-II - USE OF D'-VALUES

Using a Rank-Rating method, d' values were obtained for stimuli from a model system using 15-point, 9-point, 7-point and 5-point category sc ales. For an apple/grape juice system, d' values were compared for 9-p oint and 7-point scales. There was general agreement on d' values amon g the scales, except where stimuli had their scores 'bunched' into one category: this tended to occur for the strongest and weakest stimuli for Rank-Rating and for the scales with fewer points. Bunching altered distribution variances and distorted the calculated d' values. Furthe r study gave d' values for the discrimination of confusable stimuli, u sing paired-comparison and rating data, thus providing numerical measu res of their relative sensitivity.