Scheike T H, Jensen T K
Department of Biostatistics, University of Copenhagen, Denmark.
Biometrics. 1997 Mar;53(1):318-29.
Time to pregnancy, the number of menstrual cycles it takes a couple to conceive, and various covariates have been collected among couples ultimately achieving conception. To assess the influence of the covariates, we constructed a discrete survival model that allows time-dependent covariates. A random effect was included to account for unobserved heterogeneity. The collected waiting times are obtained through retrospective ascertainment and are analyzed as truncated data. Maximum likelihood estimation was implemented by Fisher scoring through iteratively reweighted least squares.
受孕时间、夫妻受孕所需的月经周期数以及各种协变量已在最终成功受孕的夫妻中收集。为了评估协变量的影响，我们构建了一个允许时间依存协变量的离散生存模型。纳入了一个随机效应以考虑未观察到的异质性。收集到的等待时间是通过回顾性确定获得的，并作为截断数据进行分析。最大似然估计通过迭代加权最小二乘法的Fisher评分实现。
