Vilijandas Bagdonavicius

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The proportional hazards (Cox) model is generalized by assuming that at any moment the ratio of hazard rates is depending not only on values of covariates but also on resources used until this moment. Relations with generalized multiplicative, frailty and linear transformation models are considered. A modified partial likelihood function is proposed, and(More)
We present a model and semiparametric estimation procedures for analysis of survival data with cross-effects (CE) of survival functions. Finite sample properties of the estimators are analyzed by simulation. A goodness-of-fit test for the proportional hazards model against the CE model is proposed. The well known data concerning effects of chemotherapy and(More)
The paper considers linear degradation and failure time models with multiple failure modes. Dependence of traumatic failure intensities on the degradation level are included into the models. Estimators of traumatic event cumulative intensities, and of various reliability characteristics are proposed. Prediction of residual reliability characteristics given(More)
Applications of the additive accumulation of damages (AAD) or the accelerated failure time (AFT) and the proportional hazards (PH) models in accelerated life testing with step-stresses are discussed. A new model including AAD and PH models is proposed. It is more reasonable than the PH model and wider then the AAD model. Constructing the maximum likelihood(More)
The paper considers the statistical analysis of aging and degradation processes in the elderly. The role played by dementia and sex in the loss of functional autonomy in elderly patients, in terms of progression and recovery, through several stages of increasing disability is analysed. The conjoint accelerated degradation model for statistical analysis of(More)
A survey of statistical methods for validation of shape-scale families of probability distributions from type II censored samples is given. We propose "integrated likelihood ratio tests" which are modifications of Zhang's tests from complete to type II censored data. We also give modifications of Cramér-von-Mises and Anderson-Darling tests using integration(More)
We propose new two and k-sample tests for evaluating the equality of survival distributions against alternatives that include crossing of survival functions, and proportional and monotone hazard ratios. The tests allow for right censored data. The asymptotic power against local alternatives is investigated. Simulation results demonstrate that the new tests(More)