Subjective phenomena in drug trials.

Three types of problem arise from subjective phenomena in drug trials: problems of control, measurement, and analysis. Examples are given in order to illustrate these three aspects and to present some recent advances in clinical pharmacology. The author discusses the control of drug compliance, the validity of questionnaires, the subjectivity of the observer and that of the observations. Drug side-effects and the statistical analysis of qualitative data are presented in more detail.