ABSTRACT
Reported falls in human sperm counts in many developed countries have serious implications for the future of mankind. In fecundability studies, data are collected on waiting times to conception in human beings, as well as on variables such as age and body mass index, which is a measure of obesity. For instance, the paper by Jensen et al. (1998) concluded that the probability of conception in a menstrual cycle was lowered if only five alcoholic drinks were taken by the woman each week. Data from studies such as this require appropriate statistical analysis, which quite often results from describing the data by means of models tailored specifically to the particular question of interest.
