In the second article of our series on epidemiology Mona Okasha explains the different types of study involved
Epidemiology may seem difficult to understand. It has concepts and words very different to those that you come across in the rest of your medical training. In this article I give an overview of what types of studies are available to us, with examples of when and when not to consider each type. I have not included an exhaustive list of advantages and disadvantages; these are available in most textbooks. The next article will concentrate on how to interpret study results.
In an ecological study, we would compare rates of orgasm and death across different geographical areas. But how would we find out orgasm rates per area? And would these differ sufficiently across areas to be able to correlate them with death rates?
A cross sectional study by its nature excludes dead people. We could do a survey of women, asking them about the frequency of their partner's orgasms, and