Topics: Basic ideas of latent state-trait-theory, Singletrait model, multistate model and multistate-singletrait model, Analysis of a probit multistate model with the life-satisfaction scale (3 times points), Analysis of this model with the additional constraint: The correlations of the three latent state variables are equal to 1, Analysis of a probit singletrait model with the life-satisfaction scale (3 times points), Differences between the last two models