Fig. 4From: Rasch modelling to deal with changes in the questionnaires used during long-term follow-up of cohort studies: a simulation studyThe four scenarios for items shared by the questionnaires across time. Bold items are those available to calculate the raw score, grey items are additional items available to compute the standardised score and to estimate the latent variable score. δj: value for the difficulty of item j as set in the simulation modelBack to article page