Fig. 2

Category probability curves for two items of J-EAT-10. The y-axis represents the probability of observing each category of the five response options on J-EAT-10 at each level of item difficulty on the x-axis. Each colour corresponds to the different response options: 0 = blue, 1 = red, 2 = green, 3 = purple, 4 = pink. The intersections of adjacent curves are the thresholds. a The category probability curves for item 9 (Cough) with ordered thresholds. The responses to this item are distributed in a logical progressive order, and as a respondent’s OD severity increases, so the probability of achieving the next score increases. b The category probability curves for item 3 (Liquids effort) with disordered thresholds. The responses to this item are not distributed in a logical progressive order, and a score of 1 or 3 is never probable