Consistent Estimation of the Structural Distribution Function

Motivated by problems in linguistics we consider a multinomial random vector for which the number of cells N is not much smaller than the sum of the cell frequencies, i.e. the sample size n . The distribution function of the uniform distribution on the set of all cell probabilities multiplied by N is called the structural distribution function of the cell probabilities. Conditions are given that guarantee that the structural distribution function can be estimated consistently as n increases indefinitely although n / N does not. The natural estimator is inconsistent and we prove consistency of essentially two alternative estimators.     

Identifiable finite mixtures of location models for clustering mixed-mode data

For clustering mixed categorical and continuous data, Lawrence and Krzanowski (1996) proposed a finite mixture model in which component densities conform to the location model. In the graphical models literature the location model is known as the homogeneous Conditional Gaussian model. In this paper it is shown that their model is not identifiable without imposing additional restrictions. Specifically, for g groups and m locations, (g!)m–1 distinct sets of parameter values (not including permutations of the group mixing parameters) produce the same likelihood function. Excessive shrinkage of parameter estimates in a simulation experiment reported by Lawrence and Krzanowski (1996) is shown to be an artifact of the model's non-identifiability. Identifiable finite mixture models can be obtained by imposing restrictions on the conditional means of the continuous variables. These new identified models are assessed in simulation experiments. The conditional mean structure of the continuous variables in the restricted location mixture models is similar to that in the underlying variable mixture models proposed by Everitt (1988), but the restricted location mixture models are more computationally tractable.     

Estimation for hidden Markov random fields

A finite state Markov random field is noisily observed via a second finite state process. The parameters of the model are estimated, as well as the most likely signal given the observations.     

Child-Oriented Family Therapy Outcome Research: Comparisons Between Brief Family Therapy and an Alternative Treatment

This paper is concerned with outcome research in child-oriented family therapy. Nine investigations comparing brief family therapy with an alternative treatment were critically reviewed. All of the studies were vulnerable to criticisms on design and methodological grounds. Problem areas included: specification of therapeutic techniques, confounding of therapeutic variables, equivalence of therapist factors, measurement of outcome, adequacy of measures and appropriate use of control groups. All studies concluded that childhood problems could be treated successfully with brief family therapy techniques. However, in the light of the design problems listed above, these conclusions should be treated tentatively.     

Establishing verbal repertoires: Toward the application of general case analysis and programming

A great deal of clinical and experimental work in past decades has focused on establishing functional verbal repertoires that are used across various settings and situations by persons with moderate and severe disabilities. Such work has not always involved a careful analysis and programming approach for structuring training to achieve the desired range of stimulus control relationships. General case analysis and programming procedures, which are based on behavior analytic and Direct Instruction principles and techniques, have proven effective in recent years for teaching a variety of community-based skills to learners with moderate and severe disabilities. This paper outlines the general case process and discusses its application to establish verbal repertoires.

     

The Significance of Shift Work: Current Status and Future Directions

This paper provides a review and synthesis of research literature on the effects of shift work on workers’ physical health, mental health/well-being, and family life. The focus is on current knowledge, unanswered questions, and new directions for future research. The selection of research literature is guided by a general conceptual framework that identifies predictor variables, moderating variables, and outcome variables. The paper concludes with a discussion of the variables that should be incorporated into an agenda for future research.     

Markov bridges and enlarged filtrations

The semimartingale decomposition of a Markov chain, whose value at some future time is known, is obtained by considering an enlarged filtration.