A mere few years ago it would have seemed odd to propose a Handbook on the treatment of management problems within a sphere of uncertainty. Even today, on the threshold of the third millennium, this statement may provoke a certain wariness. In fact, to resort to exact or random data, that is probable date, is quite normal and con­ venient, as we then know where we are going best, where we are proposing to go if all occurs as it is conceived and hoped for. To treat uncertain information, to accept a new principle and from there determined criteria, without being sure of oneself and confiding only in the will to better understand objects and phenomena, constitutes and compromise with a new form of understanding the behaviour of current beings that goes even further than simple rationality. Economic Science and particularly the use of its elements of configuration in the world of management, has imbued several generations with an analytical spirit that has given rise to the elaboration of theories widely accepted by the international scientific community. In this work we are proposing something a little more modest: to use, in the best possible way, data and information that are available for drawing up and applying techniques and instruments that are useful for current reality within the world of businesses and institutions, in an attempt to mislead ourselves as little as possible.