Final answer:
A cross-sectional study is an observational study that collects data from a sample of subjects at one point in time to analyze the prevalence of factors or health outcomes in a population.
Step-by-step explanation:
An observational study that assesses aggregate data collected at the population level for exposures and/or outcomes is known as a cross-sectional study. This type of study takes a snapshot of a sample of subjects at a single point in time. For example, early suggestions of a possible link between smoking and lung cancer emerged from cross-sectional studies, which found a higher rate of lung cancer among smokers when compared to non-smokers at that point in time. The primary characteristic of a cross-sectional study is that it is not prospective like a cohort study, which follows subjects over time. Instead, cross-sectional studies provide valuable information on the prevalence of factors or outcomes within a given population at a specific time, offering insights into associations which can be further explored in more analytical epidemiological research.
It's critical in an observational study like a cross-sectional study to define the population precisely, as most epidemiological measures are made with reference to the size of the population at risk. Without manipulating or controlling variables, researchers use these studies to draw associations between various factors and health outcomes, contributing fundamentally to the fields of public health and epidemiology.