In many problems in science and practice, the following questions arise: Which one of two or more alternative states is present or which event will occur? Which factors are suitable for the decision or prognosis and what influence do they have on the occurrence of a state or event? Often, only two alternative states or events are involved, as in the question whether a patient has a certain disease or not. Logistic regression can be used to answer such questions. The logistic regression is similar to discriminant analysis with regard to the problem definition. The main difference between the two methods is that logistic regression directly provides probabilities for the occurrence of the alternative states or the affiliations to the individual groups.