In model 1 of Example 7.5, try a scale mixture version for the random effects \(b_{i, 1: 2}\) with degrees of freedom an unknown (equivalent to a bivariate Student \(t\) ). The analysis may be sensitive to the prior adopted for the degrees of freedom (e.g. a uniform between 4 and 100, an exponential with unknown mean, etc.). Are there any clear outliers (scale factors clearly under one)?

Data from Example 7.5

To illustrate longitudinal approaches for ordinal responses, consider data on the impacts of drug treatments on symptom severity among n = 324 schizophrenic patients, collected as part of the NIMH Schizophrenic Collaborative Study (Hedecker and Gibbons, 1994). There were originally four treatments: chloropromazine, fluphenazine, thioridazine, and placebo. Since previous analysis revealed similar effects of the three anti-psychotic drugs, the treatment is