Which type of epidemiological study?

A key issue in epidemiology is to choose an appropriate study design. The design chosen will depend on the question of interest and some designs will offer clear advantages over others. However, other factors such as current state of knowledge will be important. The decision will be based not only on methodological but also on practical considerations, including the resources available, and the speed with which a result is required. For example, the most appropriate study may be too expensive or take too long to provide an answer. In such circumstances a compromise will need to be made—to undertake a study which can be conducted within the budget and time available, and which delivers information that is suitable for addressing the question of interest.