The Methodology of Controlled Clinical Trials

Abstract

The comparison of two groups differently treated is based mainly on two principles:

• a) the comparison between the 2 groups must be made through significance tests which enable one to know if the difference is reasonably attributable to chance or if, on the contrary, it is significant;

• b) if the difference is significant, it can be explained by the treatments alone only if the groups are comparable in every respect, except for treatments. They must be chosen comparable, from the start, which can only be done properly through randomisation and the comparability must be maintained as well as from the point of view of the evolution of the disease (of course, outside the effects of the treatments), as from that of the evaluation of this evolution which sometimes entails blind readings and even blind trials or double blind.