One of the features of below replacement fertility level is increasing first birth interval which
has occurred in recent years in Iran. According to importance of using valid statiatical
methods for analyzing first birth interval, in this article parametric survival method were
introduced and compared by nonparametric survival methods for data in fertility and
marriage attitudes survey in Semnan. Data were contained 390 married women aged 15–49
years old collected by stratified sampling method in Semnan, 2013. In univariate survival …