The Cox proportional hazards model is ubiquitous in time-to-event studies of political processes. Plausible deviations from correct specification and operationalization caused by problems such as measurement error or omitted variables can produce substantial bias when the Cox model is estimated by conventional partial likelihood maximization (PLM). One alternative is an iteratively reweighted r...

This paper presents a method for estimating a class of panel data duration models, under which an unknown transformation of the duration variable is linearly related to the observed explanatory variables and the unobserved heterogeneity ~or frailty! with completely known error distributions+ This class of duration models includes a panel data proportional hazards model with fixed effects+ The p...

A new approach for analyzing state duration data in brand-choice studies is explored. This approach not only incorporates the correlation among repeated purchases for a subject, it also models the purchase timing and the brand decision jointly. The former is accomplished by applying transition model approaches from longitudinal studies while the latter is done by conditioning on the brand choic...

Correspondence to Dr Michael Nurmohamed; [email protected] ABSTRACT Objective: To assess the effects of treatment with antitumour necrosis factor (TNF) agents, methotrexate, or other non-biological disease-modifying antirheumatic drugs (DMARDs) on cardiovascular event risks among patients with rheumatoid arthritis (RA). Methods: We conducted a retrospective study using data from the MarketScan...

It is common for large population-based surveys to select a sample from a population using a complex design. A simulation study was conducted to compare the estimates from the stratified proportional hazards model with the weighted estimates of the Binder method, when a stratified random sample of the population is used. The SAS PHREG procedure performs regression analysis of survival data base...

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...

We extend the proportional hazards model to a two-level model with a random intercept term and random coefficients. The parameters in the multilevel model are estimated by a combination of EM and Newton-Raphson algorithms. Even for samples of 50 groups, this method produces estimators of the fixed effects coefficients that are approximately unbiased and normally distributed. Two different metho...

This paper presents a simple way to handle missing values in categorical covariates, namely conditional probability imputation . Properties of this technique are given for various patterns of missing data in regression studies . An example shows its use in the proportional hazards model . The probability imputation technique is furthermore compared with multiple imputation and model-based appro...