Canadian Health Information Management Association Practice Exam

What is a major difficulty in an epidemiologic experiment comparing two cities?

1. The cities may not be of equal population

2. The case and control groups may not be comparable

3. The groups studied may not be representative

4. There may be bias in determining the factor

The correct answer is: The case and control groups may not be comparable

In an epidemiologic experiment comparing two cities, a major difficulty arises from the fact that the case and control groups may not be comparable. This is crucial because for the validity of the study, it's essential that the groups being compared are as similar as possible, except for the exposure of interest. If the case group (those with the disease or condition) and the control group (those without) are not matched appropriately or share different characteristics that could influence the outcome, any observed differences may be skewed or misleading. This lack of comparability can lead to confounding factors that obscure the true relationship between the exposure and the outcome being studied. Furthermore, while population size disparities, representativeness of groups, and biases in determining factors can also present challenges in epidemiologic studies, the fundamental issue of comparability directly impacts the ability to draw accurate conclusions about the relationship being investigated, making it a significant difficulty in the context of comparing two cities.