An epidemiological study looks for a strong correlation between a specific factor and a disease.Analytical epidemiology concerns the “how” and the “why” questions of an epidemic—explaining how and why an epidemic occurs. To find the answers to these questions, we rely on conducting epidemiological studies to prove or disprove our hypotheses we make about the cause of the disease (based on descriptive epidemiology). Epidemiological studies look closely at the statistical relationship between a factor (exposure) and the disease, allowing us to see whether a certain factor is associated with, or causes a disease.
An epidemiological study looks for a strong correlation between a specific factor and a disease. For example, data that shows that 90% of people in the study that were exposed to a particular factor “X,” developed disease “Y” may be a strong indication that factor “X” causes disease “Y.” But however strong the correlation may be, something that must be kept in mind is that epidemiological studies only involve numbers and statistics. In order to come to a conclusion, the data must be brought to life, to find a reasonable story to explain what happened. A conclusion that explains the data must make sense—in other words, it must be based on a strong association, it must be consistently true when the experiment is duplicated, and it must be biologically possible.
Participants in a study may omit important information, or refuse to answer altogether because they are busy. These are called "nonresponse", and can influence the results of a survey.
In carrying out epidemiological studies, the fact that the data is being collected from humans is a very important fact to remember. The data that is collected may sometimes not be completely accurate, because participants in a study might recall the information differently than what actually happened—for example, someone may accidentally omit a small, but important piece of information, or just not remember details correctly. This is always something that must be kept in mind when conducting a study.
Sources:
Jha, Prabhat, and Witold A. Zatonski. "“Smoking and Premature Mortality: Reflections on the Contributions of Sir Robert Doll”." JAMC (August 2005).
“Introduction to Basic Epidemiology and Principles of Statistics for Tropical Diseases Control”. World Health Organization. 2002.
"Steps of an Outbreak Investigation." Centers for Disease Control and Prevention.
"The Man Who Saved a Million Lives." The Observer 24 Apr. 2005.
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