The objective of this book is to collect and simplify what has been done in the study of extreme values theory. This branch is interested in rare events and the causes of all disasters we know and of all economic crises. In addition, the second objective is to present an introduction that is devoted to the basic notions of survival analysis. Furthermore, we present two cases of incomplete data (censored and truncated) with giving the non-parametric estimator of the mean for each case.