MEASUREMENT OF THE AVERAGE VALUES OVER OBSERVER'S CONFIDENCE-RATING LEVELS BY THE METHOD OF SUCCESSIVE CATEGORIES

ROC analysis and rating by cumulated points have been widely employed for visual evaluations regarding medical images, which have no objective interval scales of the observer's confidence levels to categories in which their judgements regarding the presence or absence of subtle signals are ranked based on different types of point confidence-rating scales. By the method of successive categories, measurements of mean values over their confidence levels to categories and distances among them were carried out under the following assumptions. Observers ranked their judgements regarding the presence or absence of subtle signals on a 5-point confidence-rating scale. Their interpretation of the rating scale should be kept constant throughout this experiment. There experimental results suggest that the interval scales of confidence level of the rating to categories depend on the observers.