... person's level of, for example, mental well-being, and the level of well-being expressed by the item. The model can be expressed in the form of a logit model:where ln is the normal log, P is the probability ... data from the full 14item scale was fitted to the Rasch model independently forThreshold map for the 14 item scaleFigure 1Threshold map for the 14 item scale. (See additional file 1 for full ... For example, in the case of measuring mental well-being, males andfemales should have the same probability of affirming anitem (in the dichotomous case), at the same level of mentalwell-being....