Fig. 3From: The COPD-SIB: a newly developed disease-specific item bank to measure health-related quality of life in patients with chronic obstructive pulmonary diseaseOption response curves as estimated using the GRM (on the right), and parametric smoothed regression lines based on a GAM (on the left) for an item with good fit to the GRM (item 27), and one with bad fit (item 10)Back to article page