8 resultados para stratified random sampling

em DigitalCommons@The Texas Medical Center


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The purpose of this study was to design, implement and evaluate the effectiveness of a date rape prevention program among new students at Rice University. Six-hundred and fifteen new students were randomly assigned to one of eight residential colleges or dormitories. The distribution of students to each of the dormitories was carried out in accordance with a stratified random sampling procedure. The study population was divided into strata based on ethnicity, gender, geographical region, and academic major. The number of students randomly assigned to each of the eight dormitories was approximately 75. After this procedure was completed, each of the colleges was randomly selected to either the intervention or control group. A randomized pretest and posttest control group design was used to assess changes in attitudes, self-efficacy, and behavior with regard to date rape. All participants were given an anonymous pretest and posttest measuring attitudes, self-efficacy, and behavior immediately prior to and following the intervention. The intervention group attended the play Scruples, designed to promote date rape prevention, after which they were immediately posttested. After this initial posttest the intervention group also participated in an interactive group role-playing activity led by trained peer instructors. The control group was pretested and subject to the placebo intervention of a multiculturalism play and was posttested immediately afterwards. Later in the week this group saw the Scruples play only. Both control and intervention groups were sent a two month follow-up survey questionnaire, to measure any changes in attitudes, self-efficacy, and behavior over time. As hypothesized students who saw the play Scruples showed a change in attitudes immediately posttest but no difference in self-efficacy or behavior. The two month follow-up survey showed no change in attitudes, self-efficacy, or behavior. There was a difference at pretest in males and females attitudes, with males showing significantly more rape tolerant attitudes than females. Thus, the proposed research findings will provide a better understanding of the attitudes that perpetuate date rape, and will inform strategies for prevention programs. ^

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Background. Accurate measurement of attitudes toward participation in cancer treatment trials (CTs) and cancer prevention trials (CPTs) across varied groups could assist health researchers and educators when addressing attitudinal barriers to participation in these trials. ^ Methods. The Attitudes toward Cancer Trials Scales (ACTS) instrument development was based on a conceptual model developed from research literature, clinical practice experience, and empirical testing of items with a sample of 312 respondents. The ACTS contains two scales, the Cancer Trials (CT) scale (4 components; 18 items) and the Cancer Prevention Trials (CPT) scale (3 components; 16 items). Cronbach's alpha values for the CT and CPT scales, respectively, were 0.86 and 0.89. These two scales along with sociodemographic and cancer trial history variables were distributed in a mail survey of former patients of a large cancer research center. The disproportionate stratified probability sampling procedure yielded 925 usable responses (54% response rate). ^ Results. Prevalence of favorable attitudes toward CTs and CPTs was 66% and 69%, respectively. There were no significant differences in mean scale scores by cancer site or gender, but African Americans had more favorable attitudes toward CTs than European Americans. Multiple regression analysis indicated that older age, lower education level, and prior CT participation history were associated with more favorable attitudes toward CTs. Prior CT participation and prior CPT participation were associated with more favorable attitudes toward CPTs. Results also provided evidence of reliability and construct validity for both scales. ^ Conclusions. Middle age, higher education, and European American ethnicity are associated with less positive attitudes about participating in cancer treatment trials. Availability of a psychometrically sound instrument to measure attitudes may facilitate a better understanding decision making regarding participation in CTs and CPTs. It is this author's intention that the ACTS' scales will be used by other investigators to measure attitudes toward CTs and CPTs in various groups of persons, and that the many issues regarding participation in trials might become more explicit. ^

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Currently there is no general method to study the impact of population admixture within families on the assumptions of random mating and consequently, Hardy-Weinberg equilibrium (HWE) and linkage equilibrium (LE) and on the inference obtained from traditional linkage analysis. ^ First, through simulation, the effect of admixture of two populations on the log of the odds (LOD) score was assessed, using Prostate Cancer as the typical disease model. Comparisons between simulated mixed and homogeneous families were performed. LOD scores under both models of admixture (within families and within a data set of homogeneous families) were closest to the homogeneous family scores of the population having the highest mixing proportion. Random sampling of families or ascertainment of families with disease affection status did not affect this observation, nor did the mode of inheritance (dominant/recessive) or sample size. ^ Second, after establishing the effect of admixture on the LOD score and inference for linkage, the presence of induced disequilibria by population admixture within families was studied and an adjustment procedure was developed. The adjustment did not force all disequilibria to disappear but because the families were adjusted for the population admixture, those replicates where the disequilibria exist are no longer affected by the disequilibria in terms of maximization for linkage. Furthermore, the adjustment was able to exclude uninformative families or families that had such a high departure from HWE and/or LE that their LOD scores were not reliable. ^ Together these observations imply that the presence of families of mixed population ancestry impacts linkage analysis in terms of the LOD score and the estimate of the recombination fraction. ^

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The level of compliance with clinical practice guidelines for patients with Type II Diabetes Mellitus was evaluated in 157 patients treated at BAMC from 1 January 2006 to 1 January 2007. This retrospective analysis was conducted reviewing data from medical records and following the VA/DOD protocols that health care providers are expected to follow at this facility. Data collected included patient’s age and gender, presence or absence of complications of diabetes, physical examination findings, glycemic and lipid control, eye care, foot care, kidney function, and self-management and education. Subjects were selected performing systematic random sampling, and included both male and female patients, from a variety of ages and ethnic groups. The Diabetes complications screened for included glycemic and lipid complications, retinopathy, cardiovascular complications, peripheral circulation complications, and nephropathy. The results revealed that 19.10% had no complications and that the most common complications were: cardiovascular (49.68%), glycemic and lipid control (10.82%), retinopathy and peripheral circulation (8.28% each), and nephropathy (2.54%). Only 2.54% of the records reviewed did not include information on complications. Strictly following the Department of Defense guidelines, six treatment modules were evaluated independently and together to get a final percentage of adherence to the clinical practice guidelines. It was established that the level of adherence was going to be graded as follows: Extremely deficient: 0-15%; very poor: 16-30%; Poor and in need of improvement: 31-45%. Acceptable: 46-60%; Good: 61-80%, and Excellent: 81-100%. The results indicated that the percentage of physicians' adherence to each protocol was as follows: 88.31%, 89.93%, 90.63%, 89.42%, 89.42% and 89.64%. When the results were pooled, the level of adherence to the clinical practice guidelines was 89.55%, proving my hypothesis that Brooke Army Medical Center physicians have excellent adherence to the standard protocols for Diabetes Type II to treat their patients. ^

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Although long distance running clearly has benefits--as witnessed by its popularity--it also has risks of injury and death. Little is known, however, about the prevalence of potentially dangerous training habits in long distance runners, although anecdotal information suggests that many runners have erroneous beliefs about risks and benefits of marathon running. We conducted a cross-sectional survey to estimate the prevalence of 19 potentially dangerous training habits (risky behaviors) among marathon runners. A 66-item self-administered questionnaire was mailed to a stratified random sample of runners who finished of the 1992 Houston-Tenneco Marathon and were 21-71 years of age. Responses were obtained from 508 runners (83%) with approximately equal representation in four age-gender groups: men $<$40 years, men $\ge$40 years, women $<$40 years, and women $\ge$40 years.^ Prevalences of risky behaviors were high. 50% or more ran in dangerously hot and humid conditions, did not cool down or stretch after running, did not wear proper running gear, or ran when injured or ill; 25-49% did not warm up, ran on dangerous surfaces, did not drink sufficient water during training, increased weekly mileage too quickly, and ran during lightning storms; 10-24% ran daily, ran in areas with high pollution, ran in the same direction as traffic, did hard runs frequently, ran more than 60 miles per week, or ran against the advice of a physician.^ Positive associations were found between the practice of risky behaviors and self-reported prevalence of musculoskeletal injuries, heat-related injuries, noncompliance with recommendations for preventive health examinations, and noncompliance with positive health habits.^ These results indicate that many marathon runners engage in training habits that may increase risk of substantial injury or illness. Further studies are needed to explore the association of risky training behaviors on the incidence of injuries, and to determine reasons for noncompliance with recommendations from sports medicine specialists. ^

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Objectives. The central objective of this study was to systematically examine the internal structure of multihospital systems, determining the management principles used and the performance levels achieved in medical care and administrative areas.^ The Universe. The study universe consisted of short-term general American hospitals owned and operated by multihospital corporations. Corporations compared were the investor-owned (for-profit) and the voluntary multihospital systems. The individual hospital was the unit of analysis for the study.^ Theoretical Considerations. The contingency theory, using selected aspects of the classical and human relations schools of thought, seemed well suited to describe multihospital organization and was used in this research.^ The Study Hypotheses. The main null hypotheses generated were that there are no significant differences between the voluntary and the investor-owned multihospital sectors in their (1) hospital structures and (2) patient care and administrative performance levels.^ The Sample. A stratified random sample of 212 hospitals owned by multihospital systems was selected to equally represent the two study sectors. Of the sampled hospitals approached, 90.1% responded.^ The Analysis. Sixteen scales were constructed in conjunction with 16 structural variables developed from the major questions and sub-items of the questionnaire. This was followed by analysis of an additional 7 structural and 24 effectiveness (performance) measures, using frequency distributions. Finally, summary statistics and statistical testing for each variable and sub-items were completed and recorded in 38 tables.^ Study Findings. While it has been argued that there are great differences between the two sectors, this study found that with a few exceptions the null hypotheses of no difference in organizational and operational characteristics of non-profit and for-profit hospitals was accepted. However, there were several significant differences found in the structural variables: functional specialization, and autonomy were significantly higher in the voluntary sector. Only centralization was significantly different in the investor owned. Among the effectiveness measures, occupancy rate, cost of data processing, total manhours worked, F.T.E. ratios, and personnel per occupied bed were significantly higher in the voluntary sector. The findings indicated that both voluntary and for-profit systems were converging toward a common hierarchical corporate management approach. Factors of size and management style may be better descriptors to characterize a specific multihospital group than its profit or nonprofit status. (Abstract shortened with permission of author.) ^

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In recent years, disaster preparedness through assessment of medical and special needs persons (MSNP) has taken a center place in public eye in effect of frequent natural disasters such as hurricanes, storm surge or tsunami due to climate change and increased human activity on our planet. Statistical methods complex survey design and analysis have equally gained significance as a consequence. However, there exist many challenges still, to infer such assessments over the target population for policy level advocacy and implementation. ^ Objective. This study discusses the use of some of the statistical methods for disaster preparedness and medical needs assessment to facilitate local and state governments for its policy level decision making and logistic support to avoid any loss of life and property in future calamities. ^ Methods. In order to obtain precise and unbiased estimates for Medical Special Needs Persons (MSNP) and disaster preparedness for evacuation in Rio Grande Valley (RGV) of Texas, a stratified and cluster-randomized multi-stage sampling design was implemented. US School of Public Health, Brownsville surveyed 3088 households in three counties namely Cameron, Hidalgo, and Willacy. Multiple statistical methods were implemented and estimates were obtained taking into count probability of selection and clustering effects. Statistical methods for data analysis discussed were Multivariate Linear Regression (MLR), Survey Linear Regression (Svy-Reg), Generalized Estimation Equation (GEE) and Multilevel Mixed Models (MLM) all with and without sampling weights. ^ Results. Estimated population for RGV was 1,146,796. There were 51.5% female, 90% Hispanic, 73% married, 56% unemployed and 37% with their personal transport. 40% people attained education up to elementary school, another 42% reaching high school and only 18% went to college. Median household income is less than $15,000/year. MSNP estimated to be 44,196 (3.98%) [95% CI: 39,029; 51,123]. All statistical models are in concordance with MSNP estimates ranging from 44,000 to 48,000. MSNP estimates for statistical methods are: MLR (47,707; 95% CI: 42,462; 52,999), MLR with weights (45,882; 95% CI: 39,792; 51,972), Bootstrap Regression (47,730; 95% CI: 41,629; 53,785), GEE (47,649; 95% CI: 41,629; 53,670), GEE with weights (45,076; 95% CI: 39,029; 51,123), Svy-Reg (44,196; 95% CI: 40,004; 48,390) and MLM (46,513; 95% CI: 39,869; 53,157). ^ Conclusion. RGV is a flood zone, most susceptible to hurricanes and other natural disasters. People in the region are mostly Hispanic, under-educated with least income levels in the U.S. In case of any disaster people in large are incapacitated with only 37% have their personal transport to take care of MSNP. Local and state government’s intervention in terms of planning, preparation and support for evacuation is necessary in any such disaster to avoid loss of precious human life. ^ Key words: Complex Surveys, statistical methods, multilevel models, cluster randomized, sampling weights, raking, survey regression, generalized estimation equations (GEE), random effects, Intracluster correlation coefficient (ICC).^

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Gastroesophageal reflux disease is a common condition affecting 25 to 40% of the population and causes significant morbidity in the U.S., accounting for at least 9 million office visits to physicians with estimated annual costs of $10 billion. Previous research has not clearly established whether infection with Helicobacter pylori, a known cause of peptic ulcer, atrophic gastritis and non cardia adenocarcinoma of the stomach, is associated with gastroesophageal reflux disease. This study is a secondary analysis of data collected in a cross-sectional study of a random sample of adult residents of Ciudad Juarez, Mexico, that was conducted in 2004 (Prevalence and Determinants of Chronic Atrophic Gastritis Study or CAG study, Dr. Victor M. Cardenas, Principal Investigator). In this study, the presence of gastroesophageal reflux disease was based on responses to the previously validated Spanish Language Dyspepsia Questionnaire. Responses to this questionnaire indicating the presence of gastroesophageal reflux symptoms and disease were compared with the presence of H. pylori infection as measured by culture, histology and rapid urease test, and with findings of upper endoscopy (i.e., hiatus hernia and erosive and atrophic esophagitis). The prevalence ratio was calculated using bivariate, stratified and multivariate negative binomial logistic regression analyses in order to assess the relation between active H. pylori infection and the prevalence of gastroesophageal reflux typical syndrome and disease, while controlling for known risk factors of gastroesophageal reflux disease such as obesity. In a random sample of 174 adults 48 (27.6%) of the study participants had typical reflux syndrome and only 5% (or 9/174) had gastroesophageal reflux disease per se according to the Montreal consensus, which defines reflux syndromes and disease based on whether the symptoms are perceived as troublesome by the subject. There was no association between H. pylori infection and typical reflux syndrome or gastroesophageal reflux disease. However, we found that in this Northern Mexican population, there was a moderate association (Prevalence Ratio=2.5; 95% CI=1.3, 4.7) between obesity (≥30 kg/m2) and typical reflux syndrome. Management and prevention of obesity will significantly curb the growing numbers of persons affected by gastroesophageal reflux symptoms and disease in Northern Mexico. ^