Rasch scalability of the somatosensory amplification scale: a mixture distribution approach.

Abstract Objective Somatosensory amplification refers to a person's tendency to experience somatic sensations as inappropriately intense and involves hypervigilance concerning bodily sensations. We applied the Somatosensory Amplification Scale (SSAS) in an Internet sample of young adults (N = 3031) to test whether the SSAS is Rasch scalable. Methods We applied mixture distribution extensions of the partial credit and rating scale models to identify possible subgroups that use the response set of the SSAS in different ways. Results A partial credit model, with two latent classes, showed a superior fit to all other models. Still, one of the SSAS items had to be removed because it showed sever…