

   IInnffeerrttiilliittyy aafftteerr ssppoonnttaanneeoouuss aanndd iinndduucceedd aabboorrttiioonn

        data(infert)

   FFoorrmmaatt::

         1.     Education                 0 = 0-5  years
                                          1 = 6-11 years
                                          2 = 12+  years
         2.     age                       age in years of case
         3.     parity                    count
         4.     number of prior           0 = 0
                induced abortions         1 = 1
                                          2 = 2 or more
         5.     case status               1 = case
                                          0 = control
         6.     number of prior           0 = 0
                spontaneous abortions     1 = 1
                                          2 = 2 or more
         7.     matched set number        1-83
         8.     stratum number            1-63

   DDeessccrriippttiioonn::

        This is a matched case-control study dating from before
        the availability of conditional logistic regression.

   NNoottee::

        One case with two prior spontaneous abortions and two
        prior induced abortions is omitted.

   SSoouurrccee::

        Trichopoulos et al. (1976) Br. J. of Obst. and Gynaec.
        vol.83, pp. 645-650.

   EExxaammpplleess::

        data(infert)
        model1 <- glm(case ~ spontaneous+induced, data=infert,family=binomial())
        summary(model1)
        ## adjusted for other potential confounders:
        summary(model2 <- glm(case ~ age+parity+education+spontaneous+induced,
                        data=infert,family=binomial()))
        ## Really should be analysed by conditional logistic regression
        ## which is equivalent to a Cox model :
        if(require(survival4)){
          faketime <- rep(42,nrow(infert))
          model3 <- coxph(Surv(faketime,case)~spontaneous+induced+strata(stratum),
                        data=infert,method="exact")
          summary(model3)
          detach()# survival4 (conflicts)
        }

