Fig. 1

Item information functions (IIFs) Curves. Note. Using Baker’s criteria (a < 0.64 = very low or low, 0.65 < a < 1.34 = moderate, 1.35 < a < 1.69 = high, a > 1.7 = very high) [70], the item information function curves for items with very high item discrimination parameter estimates (a >1.7) were plotted. Such higher discriminating items provide more information with greater precision for measuring a respondent’s level of depression and are thus particularly useful. BDI-II = Beck Depression Inventory–II; CES-D = Center for Epidemiologic Studies Depression Scale; PHQ-9 = 9-item Patient Health Questionnaire; DASS-Depression = Depression subscale of the 21-item Depression, Anxiety and Stress Scale; HADS-Depression = Depression subscale of the Hospital Anxiety and Depression Scale