Fig. 2

a The Person-Item Threshold Distribution of the rescored 12-item brief MHQ. b The Person-Item Threshold Distribution of the 9-item brief MHQ. The Person-Item Threshold Distribution illustrates person ability on the top portion of the graph, and item difficulty on the bottom portion of the graph. The vertical axis represents frequency of participants and items. The horizontal axis represents the ability in logits measured by the questionnaire, which is hand disability for the brief MHQ. Negative scores (on the left) represent less hand disability and positive scores (on the right) represent more hand disability. Each bar on the graph represents the frequency of participants and the frequency of items at each level of hand disability. This graph is inspected visually in order to assess how well the item difficult and person ability match