[Planning and data analysis in prospective controlled clinical trials (author's transl)].

Planning of prospective controlled clinical trials in surgery requires the use of test and control groups, sufficiently frequent repetition of experiments, random allocation of patients to the groups (example), and balancing. The descriptive data analysis should be performed in a stepwise manner (list of new data, rank list, range, median, quartiles, histogram, mean value standard deviation). The advantages of the median-quartile-system and the prerequisites for application of various significance tests are pointed out. In the conduct of controlled clinical trials, the consultative role of experimental surgeons is proposed.