Shared parameter joint models provide a framework under which a longitudinal response and a timeto-event can be modelled simultaneously. A common assumption in shared parameter joint models has been to assume the longitudinal response is normally distributed. In this paper we instead propose a joint model which incorporates a two-part “hurdle” model for the longitudinal response, motivated in p...

For a random variable Y, denote its survival function by ( ) ( ) = SY t P Y t > , its density function by ( ) fY t , and its hazard function by ( ) ( ( ) ) Y fY t h t SY t = − . Given a covariate (vector) Z which does not depend on time Y,(Z,Y) follows a time-independent covariate PH (TIPH) model or Cox’s regression model if the conditional hazard function of | Y Z is ( ) ( ) | ( ) | | , Z Y z ...

Survival bias is a potential problem when subjects are lost to follow-up, and this selection issue may arise in a wide range of biomedical studies. Controlling for the bias is difficult because subjects may be lost due to unmeasured factors. This article presents a two-step method that adjusts for survival bias in the proportional hazards model, even when unmeasured factors influence survival. ...

Background: Nitrosamines, which are known bladder carcinogens, or their precursors are found in certain meat items, and concentrations of these compounds are especially high in bacon. Only 3 cohort studies, all with 100 case subjects, have examined the relation between meat intake and bladder cancer, and few studies have examined the relation of different meat types with bladder cancer. Objecti...

Cox proportional hazard model has been widely used for survival analysis in many areas in investigating time-to-event data. PROC PHREG in SAS has been a powerful tool used for construction of a Cox model. In addition to the STATEMENTs and OPTIONs within PHREG that have already provided the most demanded output, a little more effort on data manipulation would accomplish the calculations and gene...

We study residuals of parametric accelerated failure time (AFT) models for censored data, with the main aim of inferring the correct functional form of possibly misspecified covariates. We demonstrate the use of the methods by a simulated example and by applications to two reliability data sets. We also consider briefly a corresponding approach for parametric proportional hazards models.

GREGORY ANTHONY FEENEY. Extreme Value Theory for Non-Stationary Sequences with Applications to Air Pollution Standards. (Under the direction of PRANAB KUMAR SEN and MICHAEL JOSEPH SYMONS.) The theory on extreme values has been extended to accommodate certain non-stationary sequences. Of particular interest are -sequences of daily maximum ozone concentrations which, while exhibiting obvious non-...