Certified in Public Health (CPH) Practice Exam

Which characteristic does NOT apply to a cross-sectional study?

1. Characteristics of "case" are clearly defined

2. The study is done on a defined population

3. All members of the population should be able to experience the outcome of interest

4. Patients are followed for a sufficient period of time for outcome events to occur

The correct answer is: Patients are followed for a sufficient period of time for outcome events to occur

In a cross-sectional study, researchers collect data at one specific point in time to assess the prevalence of an outcome or characteristic within a defined population. This type of study is observational and does not involve following subjects over time, which is why it is critical to understand the nature of cross-sectional studies. The characteristic that does not apply is that patients are followed for a sufficient period of time for outcome events to occur. Cross-sectional studies do not examine changes or developments over time; they provide a snapshot of data regarding participants’ characteristics and outcomes at a single moment. This is in stark contrast to longitudinal studies, where individuals are followed over extended periods to observe how outcomes change. The other characteristics—having clearly defined case characteristics, relevant to a specific population, and ensuring that all members can experience the outcome of interest—are fundamental to cross-sectional studies. These aspects ensure that the study captures an accurate representation of the population concerning the prevalence of the condition or characteristic being investigated.