721,728 research outputs found

    An overall strategy based on regression models to estimate relative survival and model the effects of prognostic factors in cancer survival studies.

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    Relative survival provides a measure of the proportion of patients dying from the disease under study without requiring the knowledge of the cause of death. We propose an overall strategy based on regression models to estimate the relative survival and model the effects of potential prognostic factors. The baseline hazard was modelled until 10 years follow-up using parametric continuous functions. Six models including cubic regression splines were considered and the Akaike Information Criterion was used to select the final model. This approach yielded smooth and reliable estimates of mortality hazard and allowed us to deal with sparse data taking into account all the available information. Splines were also used to model simultaneously non-linear effects of continuous covariates and time-dependent hazard ratios. This led to a graphical representation of the hazard ratio that can be useful for clinical interpretation. Estimates of these models were obtained by likelihood maximization. We showed that these estimates could be also obtained using standard algorithms for Poisson regression

    A Model of Income Insurance and Social Norms

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    A large literature on ex ante moral hazard in income insurance emphasizes that the individual can affect the probability of an income loss by choice of lifestyle and hence, the degree of risk-taking. The much smaller literature on moral hazard ex post mainly analyzes how a “moral hazard constraint” can make the individual abstain from fraud (“mimicking”). The present paper instead presents a model of moral hazard ex post without a moral hazard constraint; the individual's ability and willingness to work is represented by a continuous stochastic variable in the utility function, and the extent of moral hazard depends on the generosity of the insurance system. Our model is also well suited for analyzing social norms concerning work and benefit dependency.moral hazard, sick pay insurance, labor supply, asymmetric information

    An empirical investigation of failing companies and their determinants using the hazard model in an emerging capital market

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    The purpose of this study is to highlight the predictors of financial distress during the period 1990 to 2000. Previous studies highlight the inadequacies of the MDA and the log it models and suggest that a hazard model gives a more accurate result due to its consideration of time varying co-variates. By applying the hazard model, we find that leverage, profit, cash flow, liquidity, size and growth play a significant role in explaining financial distress with 83% accuracy rate. This rate did not change much when the model is applied to the hold-out sample. We also find that multicollinearity problem is not a threat in our analysis

    NEW SEISMIC SOURCE ZONE MODEL FOR PORTUGAL AND AZORES

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    The development of seismogenic source models is one of the first steps in seismic hazard assessment. In seismic hazard terminology, seismic source zones (SSZ) are polygons (or volumes) that delineate areas with homogeneous characteristics of seismicity. The importance of using knowledge on geology, seismicity and tectonics in the definition of source zones has been recognized for a long time [1]. However, the definition of SSZ tends to be subjective and controversial. Using SSZ based on broad geology, by spreading the seismicity clusters throughout the areal extent of a zone, provides a way to account for possible long-term non-stationary seismicity behavior [2,3]. This approach effectively increases seismicity rates in regions with no significant historical or instrumental seismicity, while decreasing seismicity rates in regions that display higher rates of seismicity. In contrast, the use of SSZ based on concentrations of seismicity or spatial smoothing results in stationary behavior [4]. In the FP7 Project SHARE (Seismic Hazard Harmonization in Europe), seismic hazard will be assessed with a logic tree approach that allows for three types of branches for seismicity models: a) smoothed seismicity, b) SSZ, c) SSZ and faults. In this context, a large-scale zonation model for use in the smoothed seismicity branch, and a new consensus SSZ model for Portugal and Azores have been developed. The new models were achieved with the participation of regional experts by combining and adapting existing models and incorporating new regional knowledge of the earthquake potential. The main criteria used for delineating the SSZ include distribution of seismicity, broad geological architecture, crustal characteristics (oceanic versus continental, tectonically active versus stable, etc.), historical catalogue completeness, and the characteristics of active or potentially-active faults. This model will be integrated into an Iberian model of SSZ to be used in the Project SHARE seismic hazard assessment
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