Fig. 1From: Latent variable mixture models to test for differential item functioning: a population-based analysisWithin-class item response percentages for the SF-36 physical functioning (PF) sub-scale items. Legend: The selected best-fit latent variable mixture model had three classes. For items PF9 and PF10, response categories of “limited a lot” and “limited a little” were combined due to low frequenciesBack to article page