Fig 2. Item Characteristic Curve (ICC) and Item Information Function (IIF) of the 5 items of the Well-being Numerical Rating Scales (WB-NRSs).

Latent trait (Theta) is shown on the horizontal axis, the probability of endorsing a response option (solid line) is shown on the left vertical axis, and the amount of information (dotted line) yielded by the item at each trait level is shown on the right vertical axis.