This manual is intended for students in their second year of higher education.This manual has a unifying concept: it is a continuum whose different parts refer to each other. Its purpose is not exhaustive, but pedagogical and explanatory in order to make the essential clear and to open a wider field.We aim essentially at the following objectives:- To consolidate the knowledge already acquired- To motivate students by allowing them to apply their knowledge in concrete situations;- To make students aware of the value and limitations of the information available for decision-making.In writing this manual, we have done our best to produce a pleasant and attractive book that allows students to approach their end-of-year exams in excellent conditions. We wish them good luck.Finally, we would be very happy to receive constructive criticism and suggestions from our colleagues, for which we would like to thank them.