Abstract
Studies follow a hierarchy in terms of the quality of evidence that they can provide. Randomized double blind placebo control (RDBPC) studies are considered the "gold standard" of epidemiologic studies. And the same is discussed at length in this paper taking example of a real journal article employing this study design to answer the research question; "Does once daily dose of Valacyclovir reduce the risk of transmission of genital herpes in a susceptible partner?" RDBPC studies remain the most convincing research design in which randomly assigning the intervention can eliminate the influence of unknown or immeasurable confounding variables that may otherwise lead to biased and incorrect estimate of treatment effect. Also, randomization eliminates confounding by baseline variables and blinding eliminates confounding by co-interventions, thus eliminating the possibility that the observed effects of intervention are due to differential use of other treatments. The best comparison is placebo control that allows participants, investigators and study staff to be blinded. The advantage of trial over an observational study is the ability to demonstrate causality. Hope, this will be useful to neophyte researchers to understand causal hierarchy when critically evaluating epidemiologic literature.