an observational study that collects data from a population or a representative subset at a single point in time. It provides a “snapshot” of variables such as health status, behaviors, or exposures without following participants over a period. Cross-sectional studies are efficient for assessing prevalence and associations but are less powerful than prospective or longitudinal studies for determining causality or changes over time.
Example
A public health researcher conducts a cross-sectional study by surveying 5,000 adults in one city during June 2025 to assess the prevalence of e-cigarette use and its association with demographic factors. Data are collected only once and analyzed to estimate how common e-cigarette use is at that moment.