Clinical research is generally a matter of investigating pertinent questions regarding a condition and its management. In an ideal world, the answers to those questions are best answered by looking at every person with that condition or its risk factors. In reality, this is hardly feasible because most conditions studied can involve a very large population. To conduct any observational study in the entire population would involve prohibitive logistical and cost issues. If the study were interventional in nature, this would be almost impossible on ethical grounds given the potential risk the population would be exposed to.