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Shape Constrained Non‐parametric Estimators of the Baseline Distribution in Cox Proportional Hazards Model
Author(s) -
LOPUHAÄ HENDRIK P.,
NANE GABRIELA F.
Publication year - 2013
Publication title -
scandinavian journal of statistics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.359
H-Index - 65
eISSN - 1467-9469
pISSN - 0303-6898
DOI - 10.1002/sjos.12008
Subject(s) - mathematics , estimator , statistics , monotone polygon , efficient estimator , trimmed estimator , minimax estimator , hazard ratio , parametric statistics , invariant estimator , m estimator , minimum variance unbiased estimator , confidence interval , geometry
. We investigate non‐parametric estimation of a monotone baseline hazard and a decreasing baseline density within the Cox model. Two estimators of a non‐decreasing baseline hazard function are proposed. We derive the non‐parametric maximum likelihood estimator and consider a Grenander type estimator, defined as the left‐hand slope of the greatest convex minorant of the Breslow estimator. We demonstrate that the two estimators are strongly consistent and asymptotically equivalent and derive their common limit distribution at a fixed point. Both estimators of a non‐increasing baseline hazard and their asymptotic properties are obtained in a similar manner. Furthermore, we introduce a Grenander type estimator for a non‐increasing baseline density, defined as the left‐hand slope of the least concave majorant of an estimator of the baseline cumulative distribution function, derived from the Breslow estimator. We show that this estimator is strongly consistent and derive its asymptotic distribution at a fixed point.