The range of different study designs can be quite confusing. However, to help you navigate the maze of study designs, we can split them into groups which share common characteristics. In this module, you will be introduced to these common characteristics, and you will learn the main principles of ecological and cross-sectional studies, as well as when it is appropriate to use them. By the end of the module, you will be able to identify and critically consider the advantages and disadvantages of these study designs.

This module focuses on case-control studies, which is one of the best known epidemiological study designs. Case-control studies are particularly useful when you don’t have the luxury of waiting for a long follow-up period to conclude. In this module, you will learn the key elements of case-control study design, and you will learn how to estimate the appropriate measure of association when presented with data from a case-control study.

Cohorts were ancient Roman military units, but in modern epidemiology the word “cohort” is used to describe a group with a shared characteristic. In cohort studies, we follow groups of people over time, we collect data on their exposure and outcome, and try to estimate whether there is an association between the group-defining characteristic and the outcome of interest. In this module, you will learn how to design such a study, the kind of problems which may arise and how it compares with case-control studies. You will also learn about nested case-control and case-cohort studies, which allow us to harness the advantages of cohort studies in more efficient ways. By the end of the module, you will be able to choose the best study design in a variety of contexts.