We model the genetic behavior of a large population of individuals which is to some extent subdivided into colonies. At some stage of the life cycle there is genetic exchange among the colonies due to migration. We consider the stationary distribution of allele frequencies at a specific locus over all the colonies under various models of migration among the colonies. All of our models are variations of the Wright-Fisher Model. We consider both estimating and modeling gene flow among the colonies. / The Island Model assumes that migrants into a given colony are equally likely to come from any of the other colonies. In the Island Model with all mutations producing new alleles (the infinite-allele model), we use a moment argument to provide analytic support that the Beta (or Dirichlet) distribution is a good model for the stationary distribution of allele frequencies. In simulated data, we compare the performance of several candidate estimators of migration rate. / If migration is more likely to be from nearest-neighbor colonies, then the Stepping-Stone Model is an appropriate extension of the Island Model. For a stepping-stone migration pattern we consider the two-allele case, and study the relative frequency of allele A1 over all the colonies. The effects of various migration patterns across colonies on these relative frequencies are studied. We set down a joint distribution for the relative frequencies of A1 at the colonies. This joint distribution is Gaussian and allows us to estimate parameters that describe the extent of genetic exchange across colonies. The Gaussian Model is easy to simulate and fits well to data (possibly transformed) that has been generated according to the Stepping-Stone Model. The Gaussian Model can be extended without much difficulty to describe various mating patterns across colonies. / Source: Dissertation Abstracts International, Volume: 53-07, Section: B, page: 3252. / Major Professor: Duane Meeter. / Thesis (Ph.D.)--The Florida State University, 1992.

Source: Dissertation Abstracts International, Volume: 40-06, Section: B, page: 2498. / Thesis (Ph.D.)--The Florida State University, 1979.

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Additive and multiplicative statistical models in epidemiology invoke different assumptions regarding exposure-outcome relationships. While either may seem to provide an adequate fit in small data sets, a comparative parameter based on the correct set of assumptions will be more stable when applied in other contexts. Important implications of model selection and the scant literature on theoretical reasoning are presented. Given a lack of biological knowledge, a body of corroborative empirical knowledge would be helpful in choosing between statistical models. Traditionally, the fit of a multiplicative model is evaluated by a $ chi sp2$ test of homogeneity. However, this is a test rather than a measure and is sample-size dependent. In this thesis, the development of a new measure of heterogeneity of rate ratios, phi prime, is presented and applied to stomach cancer registry data. Results suggest homogeneity when comparing regions within countries, but some heterogeneity between continents.

A randomized controlled trial was used to evaluate the effects of a screening programme for intestinal parasite infection in newly-arrived Southeast Asian refugees. Statistically significant prevalence differences over the six-month study period were found between the screened and control groups for each refugee group from Kampuchea, Laos and Vietnam. Further analyses concentrated on the Kampuchean group because of its large number and satisfactory participation rate. / The greatest prevalence differences were found in hookworm and Ascaris infections. Continued high levels of Giardia and Strongyloides infection indicated the potential for transmission and the diagnostic challenges of imported parasites. / A statistically significant reduction in self-reported morbidity was demonstrated between the treatment groups. However, no difference in health care utilization, measured as (outpatient) contact with a physician, was found over the six-month period. / The costs of screening were estimated to exceed the costs of disease in the absence of screening. However, other considerations must be taken into account in public health policy-making in this field.

The standardized patient is one method which can be used in the measurement of clinical competence. The accuracy of reproduction of important features of the patient case by the standardized patient was evaluated in Studies 1 and 2. In 839 encounters reviewed, only 13/89 patients provided an accurate reproduction of the case. Attributes of the patient, training process and evaluation procedure were associated with better patient accuracy. A significant inverse relationship was found between patient accuracy and competence score. In Study 3, the use of standardized patients as raters of behaviour was assessed. There were systematic differences in the scoring by different raters, and overall rater agreement was r =.41.