Trajectory plots for vertigo data. Effect of betahistine-dihydrochloride on the frequency of attacks of vertigo in a total of 112 Menière’s disease patients; 2 treatment groups: “low-dosage” (50 patients) vs. “high-dosage” (62 patients). A) individual trajectories for vertigo data. B) and C) display the conditional posterior mean trajectories of the number of attacks depending upon fixed and random effects after fitting a Poisson GLMM (I: model with random intercepts. IS: model with random intercepts and slopes). The same color is used to indicate observations and model-based estimates for the same patient.