7 resultados para group membership models

em DigitalCommons@The Texas Medical Center


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Ethnic violence appears to be the major source of violence in the world. Ethnic hostilities are potentially all-pervasive because most countries in the world are multi-ethnic. Public health's focus on violence documents its increasing role in this issue.^ The present study is based on a secondary analysis of a dataset of responses by 272 individuals from four ethnic groups (Anglo, African, Mexican, and Vietnamese Americans) who answered questions regarding variables related to ethnic violence from a general questionnaire which was distributed to ethnically diverse purposive, nonprobability, self-selected groups of individuals in Houston, Texas, in 1993.^ One goal was psychometric: learning about issues in analysis of datasets with modest numbers, comparison of two approaches to dealing with missing observations not missing at random (conducting analysis on two datasets), transformation analysis of continuous variables for logistic regression, and logistic regression diagnostics.^ Regarding the psychometric goal, it was concluded that measurement model analysis was not possible with a relatively small dataset with nonnormal variables, such as Likert-scaled variables; therefore, exploratory factor analysis was used. The two approaches to dealing with missing values resulted in comparable findings. Transformation analysis suggested that the continuous variables were in the correct scale, and diagnostics that the model fit was adequate.^ The substantive portion of the analysis included the testing of four hypotheses. Hypothesis One proposed that attitudes/efficacy regarding alternative approaches to resolving grievances from the general questionnaire represented underlying factors: nonpunitive social norms and strategies for addressing grievances--using the political system, organizing protests, using the system to punish offenders, and personal mediation. Evidence was found to support all but one factor, nonpunitive social norms.^ Hypothesis Two proposed that the factor variables and the other independent variables--jail, grievance, male, young, and membership in a particular ethnic group--were associated with (non)violence. Jail, grievance, and not using the political system to address grievances were associated with a greater likelihood of intergroup violence.^ No evidence was found to support Hypotheses Three and Four, which proposed that grievance and ethnic group membership would interact with other variables (i.e., age, gender, etc.) to produce variant levels of subgroup (non)violence.^ The generalizability of the results of this study are constrained by the purposive self-selected nature of the sample and small sample size (n = 272).^ Suggestions for future research include incorporating other possible variables or factors predictive of intergroup violence in models of the kind tested here, and the development and evaluation of interventions that promote electoral and nonelectoral political participation as means of reducing interethnic conflict. ^

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Uruguay has some of the strictest tobacco-control laws in Latin America. Despite this, youth smoking rates in Uruguay are amongst the highest in South America. Thus, it is important to identify strategies to prevent youth smoking in Uruguay. The current qualitative research study sought to identify intrapersonal and socioenvironmental factors that are associated with smoking among middle school youth in Uruguay. It also sought to develop potential prevention strategies and media messages that would resonate with youth for a social media campaign. The study was grounded in social cognitive theory and the theory of reasoned action/planned behavior, among other behavioral science theories; anthropological perspectives were also considered. To achieve these goals, 29 group and individual structured interviews were conducted in two private middle schools catering to lower and higher SES youth in Montevideo, Uruguay during the summer of 2012. One hundred and three study participants, including students, parents, and teachers, were interviewed. The structured interviews were recorded, transcribed, translated, back translated, coded and analyzed. The study findings show that positive attitudes towards smoking (i.e. to be seen, to increase status, to ensure women's equality, to looking old, and to service as a rite of passage), delinquent behavior (i.e. transgression/deviant behavior), social norms that support smoking (i.e. peer pressure and modeling, group membership/sense of belonging, parental modeling, and family support), easy access and availability to tobacco (i.e. retails stores) were factors associated with youth smoking. Potential protective factors may include parental support, negative attitudes towards smoking, sports/music, and smoke-free environments. Because study participants are accustomed to government-sponsored strong countermarketing graphic imaging, study participants selected even stronger images and messages as the preferred way to receive tobacco prevention messages. Something Real ("Algo Real") was a theme that resonated with the participants and chosen as the name for the proposed campaign. This campaign was designed as a multiple component intervention that included mass, school base, and family based strategies to prevent tobacco use. Some intervention materials specific to these intervention components were developed to target relevant intrapersonal and socioenvironmental factors identified above. These materials will be tested in future pilot studies and larger scale evaluation with this population, outside the scope of this dissertation. ^

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Objective: To determine how a clinician’s background knowledge, their tasks, and displays of information interact to affect the clinician’s mental model. Design: Repeated Measure Nested Experimental Design Population, Sample, Setting: Populations were gastrointestinal/internal medicine physicians and nurses within the greater Houston area. A purposeful sample of 24 physicians and 24 nurses were studied in 2003. Methods: Subjects were randomized to two different displays of two different mock medical records; one that contained highlighted patient information and one that contained non-highlighted patient information. They were asked to read and summarize their understanding of the patients aloud. Propositional analysis was used to understand their comprehension of the patients. Findings: Different mental models were found between physicians and nurses given the same display of information. The information they shared was very minor compared to the variance in their mental models. There was additionally more variance within the nursing mental models than the physician mental models given different displays of the same information. Statistically, there was no interaction effect between the display of information and clinician type. Only clinician type could account for the differences in the clinician comprehension and thus their mental models of the cases. Conclusion: The factors that may explain the variance within and between the clinician models are clinician type, and only in the nursing group, the use of highlighting.

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Cultural models of the domains healing and health are important in how people understand health and their behavior regarding it. The biomedicine model has been predominant in Western society. Recent popularity of holistic health and alternative healing modalities contrasts with the biomedical model and the assumptions upon which that model has been practiced. The holistic health movement characterizes an effort by health care providers and others such as nurses to expand the biomedical model and has often incorporated alternative modalities. This research described and compared the cultural models of healing of professional nurses and alternative healers. A group of nursing faculty who promote a holistic model were compared to a group of healers using healing touch. Ethnographic methods of participant observation, free listing and pile sort were used. Theoretical sampling in the free listings reached saturation at 18 in the group of nurses and 21 in the group of healers. Categories consistent for both groups emerged from the data. These were: physical, mental, attitude, relationships, spiritual, self management, and health seeking including biomedical and alternative resources. The healers had little differentiation between the concepts health and healing. The nurses, however, had more elements in self management for health and in health seeking for healing. This reflects the nurse's role in facilitating the shift in locus of responsibility between health and healing. The healers provided more specific information regarding alternative resources. The healer's conceptualization of health was embedded in a spiritual belief system and contrasted dramatically with that of biomedicine. The healer's models also contrasted with holistic health in the areas of holism, locus of responsibility, and dealing with uncertainty. The similarity between the groups and their dissimilarity to biomedicine suggest a larger cultural shift in beliefs regarding health care. ^

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The use of group-randomized trials is particularly widespread in the evaluation of health care, educational, and screening strategies. Group-randomized trials represent a subset of a larger class of designs often labeled nested, hierarchical, or multilevel and are characterized by the randomization of intact social units or groups, rather than individuals. The application of random effects models to group-randomized trials requires the specification of fixed and random components of the model. The underlying assumption is usually that these random components are normally distributed. This research is intended to determine if the Type I error rate and power are affected when the assumption of normality for the random component representing the group effect is violated. ^ In this study, simulated data are used to examine the Type I error rate, power, bias and mean squared error of the estimates of the fixed effect and the observed intraclass correlation coefficient (ICC) when the random component representing the group effect possess distributions with non-normal characteristics, such as heavy tails or severe skewness. The simulated data are generated with various characteristics (e.g. number of schools per condition, number of students per school, and several within school ICCs) observed in most small, school-based, group-randomized trials. The analysis is carried out using SAS PROC MIXED, Version 6.12, with random effects specified in a random statement and restricted maximum likelihood (REML) estimation specified. The results from the non-normally distributed data are compared to the results obtained from the analysis of data with similar design characteristics but normally distributed random effects. ^ The results suggest that the violation of the normality assumption for the group component by a skewed or heavy-tailed distribution does not appear to influence the estimation of the fixed effect, Type I error, and power. Negative biases were detected when estimating the sample ICC and dramatically increased in magnitude as the true ICC increased. These biases were not as pronounced when the true ICC was within the range observed in most group-randomized trials (i.e. 0.00 to 0.05). The normally distributed group effect also resulted in bias ICC estimates when the true ICC was greater than 0.05. However, this may be a result of higher correlation within the data. ^

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When conducting a randomized comparative clinical trial, ethical, scientific or economic considerations often motivate the use of interim decision rules after successive groups of patients have been treated. These decisions may pertain to the comparative efficacy or safety of the treatments under study, cost considerations, the desire to accelerate the drug evaluation process, or the likelihood of therapeutic benefit for future patients. At the time of each interim decision, an important question is whether patient enrollment should continue or be terminated; either due to a high probability that one treatment is superior to the other, or a low probability that the experimental treatment will ultimately prove to be superior. The use of frequentist group sequential decision rules has become routine in the conduct of phase III clinical trials. In this dissertation, we will present a new Bayesian decision-theoretic approach to the problem of designing a randomized group sequential clinical trial, focusing on two-arm trials with time-to-failure outcomes. Forward simulation is used to obtain optimal decision boundaries for each of a set of possible models. At each interim analysis, we use Bayesian model selection to adaptively choose the model having the largest posterior probability of being correct, and we then make the interim decision based on the boundaries that are optimal under the chosen model. We provide a simulation study to compare this method, which we call Bayesian Doubly Optimal Group Sequential (BDOGS), to corresponding frequentist designs using either O'Brien-Fleming (OF) or Pocock boundaries, as obtained from EaSt 2000. Our simulation results show that, over a wide variety of different cases, BDOGS either performs at least as well as both OF and Pocock, or on average provides a much smaller trial. ^

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The major risk factors for liver cancer in Southeast Asia: HBV infection, aflatoxin exposure and p53 expression/mutation, were examined in experimental models. Four groups were examined for development of hepatocellular carcinoma (HCC) with and without neonatal exposure to aflatoxin (AFB$\sb1)$: (Group I.) Transgenic HBsAg mice with one p53 allele. (Group II) Transgenic HBsAg mice with two p53 alleles. (Group III) Non-transgenic litter mates with one p53 allele. (Group IV) Non-transgenic litter mates with two p53 alleles. HCC developed in Group I animals exposed to aflatoxin at an earlier time and were of a higher grade than those seen later in other groups. These results provide an explanation for as to why p53 is a target for deletion and/or mutation in human HCC especially when found in high risk areas where HBV infection and Aflatoxin B1 food contamination is high, and nicely illustrates a synergistic interaction among these three factors. None of the tumors analyzed had loss or mutation in the p53 gene.^ To determine the significance of the specific p53ser249 mutation found in HBV/aflatoxin associated human hepatomas in an in-vivo experimental model using transgenic mice, a two-nucleotide change in the mouse p53 gene at amino acid position 246, which is equivalent to that of 249 in human p53, was introduced. Transgenic mice with mutant p53 controlled by the albumin promoter were generated and shown to express the p53ser246 mutant RNA and protein specifically in liver. Three groups were examined for development of HCC with and without neonatal exposure to aflatoxin: (Group V) Transgenic p53ser246 mice with two p53 alleles. (Group VI) Transgenic p53ser246 mice with one p53 allele. (Group VII) Double transgenic for p53ser246 and HBsAg with two p53 alleles. One hundred percent of male mice with the three risk factors injected with aflatoxin developed high grade liver tumors, compared to 66.6% from group VI and only 14.2% of group V suggesting synergistic interaction between HBsAg and this particular ser246 p53 mutation.^ In order to examine the growth properties of hepatocytes and correlation with p53 loss and/or mutation, cell proliferation and ploidy analysis of liver from normal heterozyous, homozygous null mice and from transgenic mutant p53ser246, mice were studied. Loss of wild-type p53 increased G1/G0 ratios of cells as well as proliferation and decreased cell ploidy. The mutant p53ser246 did not show a significant effect on cell ploidy or proliferation. However a striking 5-10X increase in G1/G0 ratio suggests that this specific mutation specifically induces G0 to G1 transition, which in turn further predisposes hepatocytes to the damaging effect of Aflatoxin. (Abstract shortened by UMI.) ^