[Methodological deficiencies in clinical trials].

In many cases, the results obtained with clinical trials are out of all proportion to the time, money and effort invested by those participating in them. The reasons for this are to be sought, for the most part, in readily avoidable errors at the planning stage, during evaluation and during preparation for publication. Common weak points prove to be the design of the trial, patient numbers, selection of end points, characteristics of case material, blinding, randomization, exclusion from evaluation, test efficiency (power 1-beta), subgroup analyses and interim analyses.