ABSTRACT
This chapter discusses the most commonly used study designs in biomedical and epidemiological research. A research design is the framework or guide used for the planning, implementation, and analysis of data related to a specific study. The design can be used with both quantitative and qualitative methods. The main objective of using a cross-sectional type of design is to examine data across different groups at one point in time. Case-control studies involve a description of cases with and without a preexisting exposure. A case-crossover study design is useful when the risk factor/exposure is transient. In medical research studies that compare different treatment interventions, effect size is the magnitude of the difference between two or more groups. Thus, effect size can refer to the raw difference between group means, or absolute effect size, as well as standardized measures of effect, which are calculated to transform the effect to an easily understood scale.
