The objective of this work is to introduce a new method called the Survivorship Instantaneous Log-odds Ratios (SILOR); to illustrate the creation of SILOR from empirical bivariate survival functions; to also derive standard errors of estimation; to compare results with those derived from logistic regression. Hip fracture, AGE and BMI from the Third National Health and Nutritional Examination Survey (NHANES III) were used to calculate empirical survival functions for the adverse health outcome (AHO) and non-AHO. A stable copula was used to create a parametric bivariate survival function, that was fitted to the empirical bivariate survival function. The bivariate survival function had SILOR contours which are not constant. The proposed method has better advantages than logistic regression by following two reasons. The comparison deals with (i) the shapes of the survival surfaces, S(X1, X2), and (ii) the isobols of the log-odds ratios. When using logistic regression the survival surface is either a hyper plane or at most a conic section. Our approach preserves the shape of the survival surface in two dimensions, and the isobols are observed in every detail instead of being overly smoothed by a regression with no more than a second degree polynomial. The present method is straightforward, and it captures all but random variability of the data.

No description available.

The Swedish Association of Local Authorities and Regions (SALAR) and the Swedish National Board of Health and Welfare (NBHW) have published a yearly report called “Open Comparisons of Quality and Efficiency in Swedish Health Care –Regional Comparisons” since the year 2006 to compare medical outcomes, patient experience, availability and costs among hospitals and counties. In this paper, inspired by the region profiles attached to the report, we describe several possible measurement methods for comparing dichotomous data: Risk Difference (RD), Relative Risk (RR), Relative Risk Reduction (RRR) and Odds Ratio (OR), mainly by using a geometric approach as a basis for further discussion. A standard scores method is also presented as a means for more efficient comparisons.

Bachelor-Arbeit Univ. St. Gallen, 2007.

The introduction of airbags has not significantly reduced serious thoracic injury for belted occupants in frontal crashes. This thesis has investigated the effectiveness of airbags and the characteristics of residual thoracic organ injury incurred by belted occupants in vehicles equipped with airbags. This study was based on the injury outcome of over 28,000 belted front seat occupants involved in frontal collisions. Data for this analysis was extracted from National Automotive Sampling System / Crashworthiness Data System (NASS/CDS) case years 1993-2007. The use of odds ratios for comparing the effect of airbags on the occurrence of injury has shown that airbags do not significantly increase protection against head and chest injuries. Overall, the lower extremity and the upper extremity were shown to be adversely affected by airbags. The face was the only body region that was shown to benefit from the combination of seat belts and airbags as compared to seat belts alone. An investigation into the characteristics and distributions associated with thoracic organ injuries showed the heart and great vessels are the only thoracic organs that showed a significant reduction in the rate of injury with the inclusion of airbags. In vehicles with airbags, the thoracic organs are injured more frequently than the ribs. When occupants sustain thoracic organ injury, the delta-V of the crash for vehicles with and without airbags is not significantly different. The odds of serious injury to the lungs and spleen are higher for occupants in vehicles with airbags as compared to those in vehicles without airbags. Rib fracture was found to be a poor predictor of moderate to fatal thoracic organ injury. Only 31-61% of thoracic organ injuries occur with an associated rib fracture. / Master of Science

Der Zusammenhang zwischen den Begriffen "Chance" (odd) und "Wahrscheinlichkeit" (probability) und die Anwendung des Chancenverhältnisses (odds ratio) im Bereich der Biometrie und bei der logistischen Regression werden erläutert. Es wird auf mögliche Fehlinterpretationen der Begriffe Chance und Chancenverhältnis hingewiesen.

Der Zusammenhang zwischen den Begriffen "Chance" (odd) und "Wahrscheinlichkeit" (probability) und die Anwendung des Chancenverhältnisses (odds ratio) im Bereich der Biometrie und bei der logistischen Regression werden erläutert. Es wird auf mögliche Fehlinterpretationen der Begriffe Chance und Chancenverhältnis hingewiesen.

M.A. University of the Witwatersrand, Faculty of Humanities (Population Studies), 2012 / This study is based on secondary data analysis of the 1998 South African Demographic and Health Survey (SADHS) data set. The aim of the study was to identify socio-demographic, socio-economic and environmental variables that affect the survival of South African children under the age of five years. Descriptive analyses, frequency tables, Pearson’s chi-square tests of association and binary logistic regression analysis were used for data analysis in this study. Mothers who lost an under-five child were predominantly Black and rural. Such mothers were characterized by rural residential areas, relatively large family sizes, relatively poorer socioeconomic status, relatively poorer access to basic health services, relatively more child deliveries at home, and low level of education. The study showed that 269 of the 5, 066 children in the study died before celebrating their fifth birthday (5.31%). At the 5% level of significance, the survival of under-five children is significantly influenced by 2 of the 11 predictor variables found to be significantly associated in the univariate analysis and therefore included in the logistic regression analysis. These 2 predictor variables were: place of delivery of child [OR=0.97; P=0.000; CI = (0.96, 0.98)], and use of modern contraceptives by the mother [OR=0.73; P=0.002; CI = (0.59, 0.89)]. The study found that not using modern contraceptives gives a lower chance on death of a child under 5 as well as delivering at home, in the absence of a trained birth attendant. These findings are unexpected and contrary to what was found in the univariate analysis. No real explanation can be given for these findings and it would be interesting to see if the same results are found with more recent data. In order for the South African National Department of Health to fulfil its United Nations Millennium Development Goals, rural mothers and their under-five children must be provided with improved health as well as socioeconomic services.

O presente estudo se baseou em levantamentos retrospectivos e prospectivos obtidos de bovinos abatidos no Frigorífico Bertin, em Lins-SP. No primeiro levantamento consultaram-se os registros do Serviço de Inspeção Federal de ocorrência de alterações hepáticas em 1.568.821 bovinos (85% machos e 15% fêmeas), proveniente de seis Estados (SP, MS, PR, GO, MT e MG) durante os anos de 2002 a 2006. Consideraram-se os animais abatidos no último trimestre de cada ano como terminados em confinamento, sendo os demais criados continuamente em regime extensivo. Os abscessos hepáticos (1,60%) foram a segunda mais freqüente alteração hepática após a teleangectasia (1,67%). A freqüência desses abscessos foi maior em bovinos confinados (2,54%) que nos criados extensivamente (1,28%) e em fêmeas (1,85%) que em machos (1,56%). O confinamento aumenta o fator de risco (FR) de surgimento de abscessos hepáticos na ordem de 2,01 vezes. Maior freqüência de abscessos foi registrada em bovinos oriundos do Paraná, em ambos os sistemas de terminação. No levantamento prospectivo foram acompanhados o abate de 1.617 bovinos nos meses de dezembro de 2007 (n=858) e outubro de 2008 (n=759). Os abscessos hepáticos foram registrados de acordo com a freqüência, tamanho, número e localização dos mesmos em 1.617 animais; a mucosa ruminal foi avaliada (n=1.397) quanto à presença de ruminite, sua classificação e área afetada; e os pulmões (n=759) examinados para a detecção de hepatização pulmonar nas diferentes regiões, lóbos e lóbulos pulmonares, assim como grau de acometimento nos lóbulos. Foram detectados abscessos hepáticos, ruminites e pulmões hepatizados em 3,29%, 11,88% e 8,30% dos animais, respectivamente. Os abscessos estiveram igualmente distribuídos em todas as quatro regiões hepáticas, e na maioria dos casos (78,26%) os mesmos eram de pequeno tamanho (< 2,5cm) e número (até dois/órgão). Foram encontrados quatro tipos de ruminites, sendo a mais freqüente a retração cicatricial (54,22%), seguido de retalhos aderentes (24,10%), vilosidades aderidas (13,25%) e ruminite erosiva (8,43%). Em 32,53% desses casos à área afetada do rúmen ultrapassava os 300cm2. Animais com ruminite apresentavam um altíssimo risco (FR=12,67x) de manifestar abscessos hepáticos e hepatização pulmonar (FR=5,8x), com destaque para a ruminite erosiva. A hepatização pulmonar foi mais freqüente na região ventral (71,4%) que dorsal (28,6%), nos lóbulos esquerdos (59,79%) que direitos (40,21%) e na maioria dos casos acometia apenas um lóbulo (53,97%) não atingindo a hepatização mais do que 50% deste (66,6%). Abscessos hepáticos ocorreram com maior freqüência quando concomitantemente um único lóbulo pulmonar era acometido (FR=3,0x) e este se apresentava com menos de 50% de seu parênquima hepatizado (FR=11,61x). / A retrospective and prospective survey was carried out in cattle slaughtered in a private abattoir in the State of Sao Paulo, Brazil. The first survey was based on the reports done by the Federal Inspection Service of the liver condemnations among 1,568,821 cattle (85% steers; 15% cows and heifers) from six different Brazilian states during 2002 and 2006. Feedlot cattle were mostly slaughtered in the last trimester of each year, while the cattle bred extensively were in the remaining months. The abscesses (1.60%) were the second highest cause of liver condemnation after telangiectasis (1.67%). The frequency of liver abscesses were higher in feedlot cattle (2.54%) than those bred extensively (1.28%), female (1.85%) than male (1.56%). Feedlot increased the outcome (odds ratio OD= 2.01x) of liver abscess. The highest frequency of liver abscess was detected in feedlot and extensively bred cattle from the Parana state. The prospective survey was carried out following the slaughtering of 1,617 cattle during the months of December 2007 (n=858) and October 2008 (n=759). The abscesses frequency, size, number and location in the liver were recorded in all animals; the rumen mucosa (n=1,397) was examined for the presence, type and size of ruminitis; the lungs (n=759) were also examined for detection of consolidation, evaluating the affected region, number of lobes and lesion score. The following frequencies were seen: liver abscess (3.29%), ruminitis (11.88%) and lung consolidation (8.30%). The abscesses were equally distributed in all hepatic regions; most abscesses (78.2%) were small (< 2.5cm) and present in low number (1-2/liver). Four different types of ruminitis were seen: scars (54.22%), adherent contents (21.10%), clumped villi (13.25%) and erosive ruminitis (8.43%). In many cases (32.53%) the ruminitis spread to an area larger than 300cm2. Cattle with ruminitis had a very high risk of contracting liver abscesses (OD=12.67x) and lung consolidation (OR= 5.8x), principally with erosive ruminitis. Lung consolidation was mostly seen in the ventral (71.4%) than dorsal areas (28.6%), in the left (59.79%) than right lobes (40.21%); in most cases a single lobe was affected (53.97%) and less than 50% of the lobe was consolidated (66.6%). Liver abscesses were commonly seen in cattle with a single lobe (OD=3.0x) and less than 50% of this lobe consolidated (OR=11.61x).

Correlated data frequently arise from epidemiological studies, especially familial and longitudinal studies. Longitudinal design has been used by researchers to investigate the changes of certain characteristics over time at the individual level as well as how potential factors influence the changes. Familial studies are often designed to investigate the dependence of health conditions among family members. Various models have been developed for this type of multivariate data, and a wide variety of estimation techniques have been proposed. However, data collected from observational studies are often far from perfect, as measurement error may arise from different sources such as defective measuring systems, diagnostic tests without gold references, and self-reports. Under such scenarios only rough surrogate variables are measured. Measurement error in covariates in various regression models has been discussed extensively in the literature. It is well known that naive approaches ignoring covariate error often lead to inconsistent estimators for model parameters. In this thesis, we develop inferential procedures for analyzing correlated data with response measurement error. We consider three scenarios: (i) likelihood-based inferences for generalized linear mixed models when the continuous response is subject to nonlinear measurement errors; (ii) estimating equations methods for binary responses with misclassifications; and (iii) estimating equations methods for ordinal responses when the response variable and categorical/ordinal covariates are subject to misclassifications. The first problem arises when the continuous response variable is difficult to measure. When the true response is defined as the long-term average of measurements, a single measurement is considered as an error-contaminated surrogate. We focus on generalized linear mixed models with nonlinear response error and study the induced bias in naive estimates. We propose likelihood-based methods that can yield consistent and efficient estimators for both fixed-effects and variance parameters. Results of simulation studies and analysis of a data set from the Framingham Heart Study are presented. Marginal models have been widely used for correlated binary, categorical, and ordinal data. The regression parameters characterize the marginal mean of a single outcome, without conditioning on other outcomes or unobserved random effects. The generalized estimating equations (GEE) approach, introduced by Liang and Zeger (1986), only models the first two moments of the responses with associations being treated as nuisance characteristics. For some clustered studies especially familial studies, however, the association structure may be of scientific interest. With binary data Prentice (1988) proposed additional estimating equations that allow one to model pairwise correlations. We consider marginal models for correlated binary data with misclassified responses. We develop “corrected” estimating equations approaches that can yield consistent estimators for both mean and association parameters. The idea is related to Nakamura (1990) that is originally developed for correcting bias induced by additive covariate measurement error under generalized linear models. Our approaches can also handle correlated misclassifications rather than a simple misclassification process as considered by Neuhaus (2002) for clustered binary data under generalized linear mixed models. We extend our methods and further develop marginal approaches for analysis of longitudinal ordinal data with misclassification in both responses and categorical covariates. Simulation studies show that our proposed methods perform very well under a variety of scenarios. Results from application of the proposed methods to real data are presented. Measurement error can be coupled with many other features in the data, e.g., complex survey designs, that can complicate inferential procedures. We explore combining survey weights and misclassification in ordinal covariates in logistic regression analyses. We propose an approach that incorporates survey weights into estimating equations to yield design-based unbiased estimators. In the final part of the thesis we outline some directions for future work, such as transition models and semiparametric models for longitudinal data with both incomplete observations and measurement error. Missing data is another common feature in applications. Developing novel statistical techniques for dealing with both missing data and measurement error can be beneficial.