ABSTRACT
Clinical research is performed in an attempt to learn about the effects of a phenomenon in a specific population under study and extrapolate that knowledge to the truth of its effect in nature. For practical reasons, a sample of the entire population is chosen to represent the larger population of interest. In other words, the sample is chosen in a way that the results can be generalized to the larger population. This goal can be accomplished with techniques such as observational studies (cohort and crossover designs) as well as clinical trials involving an intervention, especially randomized trials with their variations and complexities.
