What type of study samples subjects at one point in time for presence or absence of exposure and disease?

The correct answer is the type of study that samples subjects at one specific point in time for both the presence or absence of exposure and disease, which is known as a cross-sectional study. This design allows researchers to assess the relationship between exposure and health outcomes at a single point in time, making it particularly useful for estimating prevalence.

In a cross-sectional study, individuals are evaluated to determine whether they have the disease of interest and if they have been exposed to a particular risk factor. This simultaneous assessment provides a snapshot of the population and can highlight associations between exposures and outcomes but does not establish cause-and-effect relationships since it doesn't track changes over time.

Other study designs such as case-control studies, longitudinal studies, and cohort studies focus on different aspects of data collection. Case-control studies look backward from outcome to exposure, comparing individuals with a condition to those without. Longitudinal studies follow subjects over time to observe changes and trends. Cohort studies involve tracking a group of individuals who share a common characteristic or experience to see how many develop a particular outcome. These designs differ fundamentally from cross-sectional studies in their approach and methodology.