Clinicians who observed the evidence for better care of their patients, should be familiar not only with some tools of critical literature reading of biomedical articles, but also with some epidemiological concepts and statistical tools that are useful to assess the validity of these studies. We are referring particularly to the measures of association and impact which permit us the ability to summarize statistical information from the articles concerned, as a summary of data and analysis and interpretation of results with both statistical and clinical significance. We understand that this is not easy because these are dry concepts, and furthermore, it is rare that health staff have incorporated probabilistic reasoning, and because ultimately, the way these results are reported is not the most didactic and practical. However, given the increasing proliferation and availability of scientific publications, it becomes more and more essential to understand these concepts and their usefulness in clinical practice. Therefore, the aim of this paper is to describe the theoretical concepts for understanding the importance of risk analysis, to know the method of calculation of the main measures of association and impact used in clinical research, as well as its interpretation and practical application in different types of study designs.