Fig. 1

Item characteristic curves (ICC) of two mis fitting items of J-EAT-10. ICC plot for two items. Based on the sample size, persons (respondents) are divided into six ability groups (class intervals with at least 50 persons in each). The curved line represents the expected scores for the item, and the dots represent the observed scores for the class intervals at the different levels of the measured variable (self-perceived OD severity). a The ICC plot for item 1 with a high positive and significant fit residual of 5.9. The observed scores form a flatter curve than the expected scores, which indicates that this item is under discriminating and might reflect multidimensionality. b The ICC plot for item 10 with a high negative and significant fit residual of − 6.3. The observed scores form a steeper curve than the expected scores, which indicates that this item is over discriminating and might reflect potential redundancy or dependency within the item set