Intended for healthcare professionals

Student Education

Epidemiological research

BMJ 2001; 323 doi: (Published 01 August 2001) Cite this as: BMJ 2001;323:0108277
  1. Mona Okasha, epidemiologist1
  1. 1University of Bristol

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.

How do I choose a study type?

  • (1) Ensure that it directly addresses your research question. There is no point performing a study which will not answer the question in hand. Many study types can address the same question, so choose a design carefully.

  • (2) Make sure the study is ethical. Epidemiology usually involves the active cooperation of patients. They usually participate for the good of research rather than for any benefit which they stand to gain. The ideal study must be ethically sound and ought to minimise the invasiveness to the participants.

  • (3) Work within your budget. Epidemiological studies tend to be much larger than other scientific experiments and resources are always limited. Patient recruitment and assessment take time and money. You need to consider the cost of collection and testing of biological samples, telephone calls and postage, and of course salaries--personnel resources have high costs attached. The cost of the research can preclude certain study designs.

  • (4) Make sure the results will be valid. The most frequent flaws in epidemiology are bias and confounding. Bias produces incorrect results and can rarely be rectified after data collection. Confounding can be addressed during statistical analysis (number crunching), provided that sufficient information was gathered during the study. Ways to …

View Full Text

Log in

Log in through your institution


* For online subscription