A Joint Modeling Approach for Longitudinal Outcomes and Non-ignorable Dropout under Population Heterogeneity in Mental Health Studies

The paper proposes a joint mixture model to model non-ignorable drop-out in longitudinal cohort studies of mental health outcomes. The model combines a (non)-linear growth curve model for the time-dependent outcomes and a discrete-time survival model for the drop-out with random effects shared by the two sub-models. The mixture part of the model takes into account population heterogeneity by accounting for latent subgroups of the shared effects that may lead to different patterns for the growth and the drop-out tendency. A simulation study shows that the joint mixture model provides greater precision in estimating the average slope and covariance matrix of random effects. We illustrate its benefits with data from a longitudinal cohort study that characterizes depression symptoms over time yet is hindered by non-trivial participant drop-out.KEYWORDS: Latent growth curve, MNAR drop-out, survival analysis, finite mixture model, mental health     

A graph-theoretical approach to the aggregation of individual preference orderings

A graph-theoretical approach as first outlined by Harary et al. is developed for solving the problem of aggregating a given set of individual preference orderings provided that no individual preferential judgment is inconsistent with the collective preference ordering obtained by aggregation.

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Evaluating a Group Home: Problems and Results

Summary The need for an evaluative framework for group homes for thementally ill is discussed. Evaluation involves separating implicitfrom explicit objectives. The possible objectives for a grouphome are considered in terms of the questions of who decideswhat the objectives are to be, how they are defined, and theirrelationship to the idea of normality. A further issue in decidingobjectives is whether the client's independence is to be foundwithin the group home or beyond it. The elements of a group home's regime are then considered: theseinclude control and group support. Problems in measuring theelements involved are mentioned. An evaluative scheme based upon this is then drawn up for aparticular group home, and the results described. The residentsare found to have experienced little change overall in theirlevel of independence, and this is associated with a regimewhere residents act in a dependent way towards staff, and staffperceptions of control and support are different from thoseof residents.