A same research question can be answered with different designs or types of studies. Know the types of studies is an essential step to through a research project to answer the question posed. In this unit, described the different designs or types of research exploring specifically in observational studies. The advantages and disadvantages to each type of observational study has outlined. On the one hand the observational descriptive studies exposing the utility troop. On the other hand, the observational analytical, such as case control and cohort with its advantages and limitations.