Fig. 2

Response category functioning for the Minimal Insomnia Symptom Scale (MISS; A), the four-item MISS (B), and the MISS-Revised (C). Areas 0–4 correspond to the five response categories (0 = no problems, 1 = minor problems, 2 = moderate problems, 3 = severe problems, 4 = very severe problems), and the borders between the respective areas are the logit threshold location on the insomnia continuum (x-axis; positive values = more insomnia) where there are equal probabilities of responding in either of the adjacent response categories