Censure (statistiques) | EPFL Graph Search

En fiabilité, la censure est le fait de prendre en compte des systèmes non-défaillants pour établir la loi de fiabilité. Plus généralement, le terme s'applique lorsque l'on ne connaît pas avec précision la date de défaillance, soit que la défaillance ne soit pas encore survenue, soit qu'elle n'ait pas été enregistrée avec précision. La censure est une information qui doit être intégrée dans le modèle de fiabilité, même si cette information est moins riche qu'un instant de défaillance défini. Types de censure Considérons que l'on suit une population de n systèmes, et que l'on enregistre l'instant de première défaillance au cours du temps. On distingue plusieurs types de censure. La censure à droite On arrête de suivre la population à un instant donné, et à ce moment-là, certains systèmes sont encore en fonctionnement. Par exemple :

on a mis des systèmes en service, et l'on désire faire un état des lieux à un instant t pour pouvoir anticiper ;
on a mis de

Contributions to Likelihood-Based Modelling of Extreme Values

Léo Raymond-Belzile

xtreme value analysis is concerned with the modelling of extreme events such as floods and heatwaves, which can have large impacts. Statistical modelling can be useful to better assess risks even if, due to scarcity of measurements, there is inherently very large residual uncertainty in any analysis. Driven by the increase in environmental databases, spatial modelling of extremes has expanded rapidly in the last decade. This thesis presents contributions to such analysis. The first chapter is about likelihood-based inference in the univariate setting and investigates the use of bias-correction and higher-order asymptotic methods for extremes, highlighting through examples and illustrations the unique challenge posed by data scarcity. We focus on parametric modelling of extreme values, which relies on limiting distributional results and for which, as a result, uncertainty quantification is complicated. We find that, in certain cases, small-sample asymptotic methods can give improved inference by reducing the error rate of confidence intervals. Two data illustrations, linked to assessment of the frequency of extreme rainfall episodes in Venezuela and the analysis of survival of supercentenarians, illustrate the methods developed. In the second chapter, we review the major methods for the analysis of spatial extremes models. We highlight the similarities and provide a thorough literature review along with novel simulation algorithms. The methods described therein are made available through a statistical software package. The last chapter focuses on estimation for a Bayesian hierarchical model derived from a multivariate generalized Pareto process. We review approaches for the estimation of censored components in models derived from (log)-elliptical distributions, paying particular attention to the estimation of a high-dimensional Gaussian distribution function via Monte Carlo methods. The impacts of model misspecification and of censoring are explored through extensive simulations and we conclude with a case study of rainfall extremes in Eastern Switzerland.

EPFL2019

Sliced inverse regression for survival data

Stephan Morgenthaler, Maya Shevlyakova

We apply the univariate sliced inverse regression to survival data. Our approach is different from the other papers on this subject. The right-censored observations are taken into account during the slicing of the survival times by assigning each of them with equal weight to all of the slices with longer survival. We test this method with different distributions for the two main survival data models, the accelerated lifetime model and Cox's proportional hazards model. In both cases and under different conditions of sparsity, sample size and dimension of parameters, this non-parametric approach finds the data structure and can be viewed as a variable selector.

Springer Verlag2014

Contributions to Likelihood-Based Modelling of Extreme Values

Léo Raymond-Belzile

EPFL2019