Emanating from classical Weibull mixture models we propose a framework for clustering survival data with various more parsimonious models by imposing restrictions on the distributional parameters. We show that these restrictions on the Weibull mixtures correspond to different proportional hazard...

Statistical experiments possess the property of adaptivity, if the ignorance of a nuisance parameter does not cause any loss in efficiency. In order to include a large variety of cases, the efficiency is measured in terms of minimax bounds. It is shown that a necessary and sufficient condition...