A<unk>  is an adequately controlled<unk>  where hypotheses are stated in advance and evaluated according to a protocol. This type of<unk>  may be implemented when it is necessary to provide additional or firm evidence of efficacy or safety. The mechanism of the<unk>  implements a key hypothesis of interest which is rigorously tested at the end of the<unk>  and directly follows the predefined primary objective of the<unk> . Of importance in a<unk>  is the process of estimating with due precision potential effects attributable to the treatment, the quantity of effects and relating these effects to their clinical significance. According to the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use:<unk> s are intended to provide firm evidence in support of claims and hence adherence to protocols and standard operating procedures is particularly important; unavoidable changes should be explained and documented, and their effect examined." Basic outline of the process of a<unk>  # A design justification and statistical aspects such as the principal features of the planned analysis, is established as part of the initial protocol. # The<unk>  should be concise in addressing only a specific number of questions. # The<unk>  should clarify key clinical questions relevant to efficacy and/or safety clearly and definitively. # The target patient population segmented for the<unk>  is clearly outlined, understood and defined as this may influence the test sites and scientists (practitioners, specialists, etc.) involved.
Confirmatory trial
Natural history study
Parallel study
Intersalt study
Clinical study design
Placebo-controlled study
Multicenter trial
Multiple baseline design