Abstract
The paper demonstrates how various parametric models for duration data such as the exponential, Weibull, and lognormal may be embedded in a single framework, and how such competing models may be assessed relative to a more comprehensive one. To illustrate the issues addressed, the survival patterns of marriages among 1203 Swedish men born 1936-1964 are studied by parametric and non-parametric survival methods. In particular, we study the sensitivity of model-choice with respect to level of aggregation of the time variable; and of covariate-effects with respect to the model chosen. In accordance with previous works our empirical results indicate that the choice of a parametric model for the duration variable is affected by the level of time aggregation. In contrast to previous results, however, our analysis shows that estimates of covariate effects are not always robust to distributional assumptions for the duration variable.

Address for Correspondence: Stockholm University, Department of Statistics, SE-106 91, Stockholm - Sweden. Tel. 46-8-162983, Fax. 46-8-167511, E-mail: Gebre@stat.su.se