The selection of patients for controlled trials.
The selection of patients for testing drugs is a very complicated process even overtly; subconscious bias must be avoided and our social conscience respected. It is of prime importance to define in advance exactly what you want to test and this may include not only the therapeutic and pharmacological effects and side-effects, the long-term neoplastic potential, the mutagenic effects and the effects on the foetus, but also mundane effects like credibility, acceptance, and even taste! Patient selection is not just "Attention there Volunteers nos. 1,3,5,7,9,....step forward smartly from the left". It is a complicated process in which there is inevitably some bias and our job is to see that any biases which are included do not bias the results, and that the results are understood to apply to this particular selection of patients and not to any other. Too many explicit exclusions therefore make results less useful because less widely relevant.
D002986:Clinical Trials as Topic; D004341:Drug Evaluation / Q000379:methods*; D004992:Ethics, Medical; D006801:Humans; D012107:Research Design