Figure 2
From: Cross-diagnostic validity of the Nottingham health profile index of distress (NHPD)
Two items with some signs of misfit in the DIF-adjusted NHPD. Item characteristic curves (ICCs) of items 9 ("everything is an effort"; panel A) and 24 ("in pain when sitting"; panel B) following scale adjustment for cross-diagnostic DIF. Black dots represent the observed responses in the sample as divided into six class intervals according to their levels of illness-related distress, indicated by red marks on the x-axis.